granicus.if.org Git - postgresql/blob - src/backend/executor/nodeMergejoin.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeMergejoin.c
   4  *        routines supporting merge joins
   5  *
   6  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/executor/nodeMergejoin.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /*
  16  * INTERFACE ROUTINES
  17  *              ExecMergeJoin                   mergejoin outer and inner relations.
  18  *              ExecInitMergeJoin               creates and initializes run time states
  19  *              ExecEndMergeJoin                cleans up the node.
  20  *
  21  * NOTES
  22  *
  23  *              Merge-join is done by joining the inner and outer tuples satisfying
  24  *              join clauses of the form ((= outerKey innerKey) ...).
  25  *              The join clause list is provided by the query planner and may contain
  26  *              more than one (= outerKey innerKey) clause (for composite sort key).
  27  *
  28  *              However, the query executor needs to know whether an outer
  29  *              tuple is "greater/smaller" than an inner tuple so that it can
  30  *              "synchronize" the two relations. For example, consider the following
  31  *              relations:
  32  *
  33  *                              outer: (0 ^1 1 2 5 5 5 6 6 7)   current tuple: 1
  34  *                              inner: (1 ^3 5 5 5 5 6)                 current tuple: 3
  35  *
  36  *              To continue the merge-join, the executor needs to scan both inner
  37  *              and outer relations till the matching tuples 5. It needs to know
  38  *              that currently inner tuple 3 is "greater" than outer tuple 1 and
  39  *              therefore it should scan the outer relation first to find a
  40  *              matching tuple and so on.
  41  *
  42  *              Therefore, rather than directly executing the merge join clauses,
  43  *              we evaluate the left and right key expressions separately and then
  44  *              compare the columns one at a time (see MJCompare).      The planner
  45  *              passes us enough information about the sort ordering of the inputs
  46  *              to allow us to determine how to make the comparison.  We may use the
  47  *              appropriate btree comparison function, since Postgres' only notion
  48  *              of ordering is specified by btree opfamilies.
  49  *
  50  *
  51  *              Consider the above relations and suppose that the executor has
  52  *              just joined the first outer "5" with the last inner "5". The
  53  *              next step is of course to join the second outer "5" with all
  54  *              the inner "5's". This requires repositioning the inner "cursor"
  55  *              to point at the first inner "5". This is done by "marking" the
  56  *              first inner 5 so we can restore the "cursor" to it before joining
  57  *              with the second outer 5. The access method interface provides
  58  *              routines to mark and restore to a tuple.
  59  *
  60  *
  61  *              Essential operation of the merge join algorithm is as follows:
  62  *
  63  *              Join {
  64  *                      get initial outer and inner tuples                              INITIALIZE
  65  *                      do forever {
  66  *                              while (outer != inner) {                                        SKIP_TEST
  67  *                                      if (outer < inner)
  68  *                                              advance outer                                           SKIPOUTER_ADVANCE
  69  *                                      else
  70  *                                              advance inner                                           SKIPINNER_ADVANCE
  71  *                              }
  72  *                              mark inner position                                                     SKIP_TEST
  73  *                              do forever {
  74  *                                      while (outer == inner) {
  75  *                                              join tuples                                                     JOINTUPLES
  76  *                                              advance inner position                          NEXTINNER
  77  *                                      }
  78  *                                      advance outer position                                  NEXTOUTER
  79  *                                      if (outer == mark)                                              TESTOUTER
  80  *                                              restore inner position to mark          TESTOUTER
  81  *                                      else
  82  *                                              break   // return to top of outer loop
  83  *                              }
  84  *                      }
  85  *              }
  86  *
  87  *              The merge join operation is coded in the fashion
  88  *              of a state machine.  At each state, we do something and then
  89  *              proceed to another state.  This state is stored in the node's
  90  *              execution state information and is preserved across calls to
  91  *              ExecMergeJoin. -cim 10/31/89
  92  */
  93 #include "postgres.h"
  94
  95 #include "access/nbtree.h"
  96 #include "catalog/pg_amop.h"
  97 #include "executor/execdebug.h"
  98 #include "executor/nodeMergejoin.h"
  99 #include "miscadmin.h"
 100 #include "utils/acl.h"
 101 #include "utils/lsyscache.h"
 102 #include "utils/memutils.h"
 103 #include "utils/syscache.h"
 104
 105
 106 /*
 107  * States of the ExecMergeJoin state machine
 108  */
 109 #define EXEC_MJ_INITIALIZE_OUTER                1
 110 #define EXEC_MJ_INITIALIZE_INNER                2
 111 #define EXEC_MJ_JOINTUPLES                              3
 112 #define EXEC_MJ_NEXTOUTER                               4
 113 #define EXEC_MJ_TESTOUTER                               5
 114 #define EXEC_MJ_NEXTINNER                               6
 115 #define EXEC_MJ_SKIP_TEST                               7
 116 #define EXEC_MJ_SKIPOUTER_ADVANCE               8
 117 #define EXEC_MJ_SKIPINNER_ADVANCE               9
 118 #define EXEC_MJ_ENDOUTER                                10
 119 #define EXEC_MJ_ENDINNER                                11
 120
 121 /*
 122  * Runtime data for each mergejoin clause
 123  */
 124 typedef struct MergeJoinClauseData
 125 {
 126         /* Executable expression trees */
 127         ExprState  *lexpr;                      /* left-hand (outer) input expression */
 128         ExprState  *rexpr;                      /* right-hand (inner) input expression */
 129
 130         /*
 131          * If we have a current left or right input tuple, the values of the
 132          * expressions are loaded into these fields:
 133          */
 134         Datum           ldatum;                 /* current left-hand value */
 135         Datum           rdatum;                 /* current right-hand value */
 136         bool            lisnull;                /* and their isnull flags */
 137         bool            risnull;
 138
 139         /*
 140          * The comparison strategy in use, and the lookup info to let us call the
 141          * btree comparison support function.
 142          */
 143         bool            reverse;                /* if true, negate the cmpfn's output */
 144         bool            nulls_first;    /* if true, nulls sort low */
 145         FmgrInfo        cmpfinfo;
 146 } MergeJoinClauseData;
 147
 148 /* Result type for MJEvalOuterValues and MJEvalInnerValues */
 149 typedef enum
 150 {
 151         MJEVAL_MATCHABLE,                       /* normal, potentially matchable tuple */
 152         MJEVAL_NONMATCHABLE,            /* tuple cannot join because it has a null */
 153         MJEVAL_ENDOFJOIN                        /* end of input (physical or effective) */
 154 } MJEvalResult;
 155
 156
 157 #define MarkInnerTuple(innerTupleSlot, mergestate) \
 158         ExecCopySlot((mergestate)->mj_MarkedTupleSlot, (innerTupleSlot))
 159
 160
 161 /*
 162  * MJExamineQuals
 163  *
 164  * This deconstructs the list of mergejoinable expressions, which is given
 165  * to us by the planner in the form of a list of "leftexpr = rightexpr"
 166  * expression trees in the order matching the sort columns of the inputs.
 167  * We build an array of MergeJoinClause structs containing the information
 168  * we will need at runtime.  Each struct essentially tells us how to compare
 169  * the two expressions from the original clause.
 170  *
 171  * In addition to the expressions themselves, the planner passes the btree
 172  * opfamily OID, btree strategy number (BTLessStrategyNumber or
 173  * BTGreaterStrategyNumber), and nulls-first flag that identify the intended
 174  * sort ordering for each merge key.  The mergejoinable operator is an
 175  * equality operator in this opfamily, and the two inputs are guaranteed to be
 176  * ordered in either increasing or decreasing (respectively) order according
 177  * to this opfamily, with nulls at the indicated end of the range.      This
 178  * allows us to obtain the needed comparison function from the opfamily.
 179  */
 180 static MergeJoinClause
 181 MJExamineQuals(List *mergeclauses,
 182                            Oid *mergefamilies,
 183                            int *mergestrategies,
 184                            bool *mergenullsfirst,
 185                            PlanState *parent)
 186 {
 187         MergeJoinClause clauses;
 188         int                     nClauses = list_length(mergeclauses);
 189         int                     iClause;
 190         ListCell   *cl;
 191
 192         clauses = (MergeJoinClause) palloc0(nClauses * sizeof(MergeJoinClauseData));
 193
 194         iClause = 0;
 195         foreach(cl, mergeclauses)
 196         {
 197                 OpExpr     *qual = (OpExpr *) lfirst(cl);
 198                 MergeJoinClause clause = &clauses[iClause];
 199                 Oid                     opfamily = mergefamilies[iClause];
 200                 StrategyNumber opstrategy = mergestrategies[iClause];
 201                 bool            nulls_first = mergenullsfirst[iClause];
 202                 int                     op_strategy;
 203                 Oid                     op_lefttype;
 204                 Oid                     op_righttype;
 205                 RegProcedure cmpproc;
 206                 AclResult       aclresult;
 207
 208                 if (!IsA(qual, OpExpr))
 209                         elog(ERROR, "mergejoin clause is not an OpExpr");
 210
 211                 /*
 212                  * Prepare the input expressions for execution.
 213                  */
 214                 clause->lexpr = ExecInitExpr((Expr *) linitial(qual->args), parent);
 215                 clause->rexpr = ExecInitExpr((Expr *) lsecond(qual->args), parent);
 216
 217                 /* Extract the operator's declared left/right datatypes */
 218                 get_op_opfamily_properties(qual->opno, opfamily, false,
 219                                                                    &op_strategy,
 220                                                                    &op_lefttype,
 221                                                                    &op_righttype);
 222                 if (op_strategy != BTEqualStrategyNumber)               /* should not happen */
 223                         elog(ERROR, "cannot merge using non-equality operator %u",
 224                                  qual->opno);
 225
 226                 /* And get the matching support procedure (comparison function) */
 227                 cmpproc = get_opfamily_proc(opfamily,
 228                                                                         op_lefttype,
 229                                                                         op_righttype,
 230                                                                         BTORDER_PROC);
 231                 if (!RegProcedureIsValid(cmpproc))              /* should not happen */
 232                         elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
 233                                  BTORDER_PROC, op_lefttype, op_righttype, opfamily);
 234
 235                 /* Check permission to call cmp function */
 236                 aclresult = pg_proc_aclcheck(cmpproc, GetUserId(), ACL_EXECUTE);
 237                 if (aclresult != ACLCHECK_OK)
 238                         aclcheck_error(aclresult, ACL_KIND_PROC,
 239                                                    get_func_name(cmpproc));
 240
 241                 /* Set up the fmgr lookup information */
 242                 fmgr_info(cmpproc, &(clause->cmpfinfo));
 243
 244                 /* Fill the additional comparison-strategy flags */
 245                 if (opstrategy == BTLessStrategyNumber)
 246                         clause->reverse = false;
 247                 else if (opstrategy == BTGreaterStrategyNumber)
 248                         clause->reverse = true;
 249                 else    /* planner screwed up */
 250                         elog(ERROR, "unsupported mergejoin strategy %d", opstrategy);
 251
 252                 clause->nulls_first = nulls_first;
 253
 254                 iClause++;
 255         }
 256
 257         return clauses;
 258 }
 259
 260 /*
 261  * MJEvalOuterValues
 262  *
 263  * Compute the values of the mergejoined expressions for the current
 264  * outer tuple.  We also detect whether it's impossible for the current
 265  * outer tuple to match anything --- this is true if it yields a NULL
 266  * input, since we assume mergejoin operators are strict.  If the NULL
 267  * is in the first join column, and that column sorts nulls last, then
 268  * we can further conclude that no following tuple can match anything
 269  * either, since they must all have nulls in the first column.  However,
 270  * that case is only interesting if we're not in FillOuter mode, else
 271  * we have to visit all the tuples anyway.
 272  *
 273  * For the convenience of callers, we also make this routine responsible
 274  * for testing for end-of-input (null outer tuple), and returning
 275  * MJEVAL_ENDOFJOIN when that's seen.  This allows the same code to be used
 276  * for both real end-of-input and the effective end-of-input represented by
 277  * a first-column NULL.
 278  *
 279  * We evaluate the values in OuterEContext, which can be reset each
 280  * time we move to a new tuple.
 281  */
 282 static MJEvalResult
 283 MJEvalOuterValues(MergeJoinState *mergestate)
 284 {
 285         ExprContext *econtext = mergestate->mj_OuterEContext;
 286         MJEvalResult result = MJEVAL_MATCHABLE;
 287         int                     i;
 288         MemoryContext oldContext;
 289
 290         /* Check for end of outer subplan */
 291         if (TupIsNull(mergestate->mj_OuterTupleSlot))
 292                 return MJEVAL_ENDOFJOIN;
 293
 294         ResetExprContext(econtext);
 295
 296         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 297
 298         econtext->ecxt_outertuple = mergestate->mj_OuterTupleSlot;
 299
 300         for (i = 0; i < mergestate->mj_NumClauses; i++)
 301         {
 302                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 303
 304                 clause->ldatum = ExecEvalExpr(clause->lexpr, econtext,
 305                                                                           &clause->lisnull, NULL);
 306                 if (clause->lisnull)
 307                 {
 308                         /* match is impossible; can we end the join early? */
 309                         if (i == 0 && !clause->nulls_first && !mergestate->mj_FillOuter)
 310                                 result = MJEVAL_ENDOFJOIN;
 311                         else if (result == MJEVAL_MATCHABLE)
 312                                 result = MJEVAL_NONMATCHABLE;
 313                 }
 314         }
 315
 316         MemoryContextSwitchTo(oldContext);
 317
 318         return result;
 319 }
 320
 321 /*
 322  * MJEvalInnerValues
 323  *
 324  * Same as above, but for the inner tuple.      Here, we have to be prepared
 325  * to load data from either the true current inner, or the marked inner,
 326  * so caller must tell us which slot to load from.
 327  */
 328 static MJEvalResult
 329 MJEvalInnerValues(MergeJoinState *mergestate, TupleTableSlot *innerslot)
 330 {
 331         ExprContext *econtext = mergestate->mj_InnerEContext;
 332         MJEvalResult result = MJEVAL_MATCHABLE;
 333         int                     i;
 334         MemoryContext oldContext;
 335
 336         /* Check for end of inner subplan */
 337         if (TupIsNull(innerslot))
 338                 return MJEVAL_ENDOFJOIN;
 339
 340         ResetExprContext(econtext);
 341
 342         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 343
 344         econtext->ecxt_innertuple = innerslot;
 345
 346         for (i = 0; i < mergestate->mj_NumClauses; i++)
 347         {
 348                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 349
 350                 clause->rdatum = ExecEvalExpr(clause->rexpr, econtext,
 351                                                                           &clause->risnull, NULL);
 352                 if (clause->risnull)
 353                 {
 354                         /* match is impossible; can we end the join early? */
 355                         if (i == 0 && !clause->nulls_first && !mergestate->mj_FillInner)
 356                                 result = MJEVAL_ENDOFJOIN;
 357                         else if (result == MJEVAL_MATCHABLE)
 358                                 result = MJEVAL_NONMATCHABLE;
 359                 }
 360         }
 361
 362         MemoryContextSwitchTo(oldContext);
 363
 364         return result;
 365 }
 366
 367 /*
 368  * MJCompare
 369  *
 370  * Compare the mergejoinable values of the current two input tuples
 371  * and return 0 if they are equal (ie, the mergejoin equalities all
 372  * succeed), +1 if outer > inner, -1 if outer < inner.
 373  *
 374  * MJEvalOuterValues and MJEvalInnerValues must already have been called
 375  * for the current outer and inner tuples, respectively.
 376  */
 377 static int32
 378 MJCompare(MergeJoinState *mergestate)
 379 {
 380         int32           result = 0;
 381         bool            nulleqnull = false;
 382         ExprContext *econtext = mergestate->js.ps.ps_ExprContext;
 383         int                     i;
 384         MemoryContext oldContext;
 385         FunctionCallInfoData fcinfo;
 386
 387         /*
 388          * Call the comparison functions in short-lived context, in case they leak
 389          * memory.
 390          */
 391         ResetExprContext(econtext);
 392
 393         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 394
 395         for (i = 0; i < mergestate->mj_NumClauses; i++)
 396         {
 397                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 398                 Datum           fresult;
 399
 400                 /*
 401                  * Deal with null inputs.
 402                  */
 403                 if (clause->lisnull)
 404                 {
 405                         if (clause->risnull)
 406                         {
 407                                 nulleqnull = true;              /* NULL "=" NULL */
 408                                 continue;
 409                         }
 410                         if (clause->nulls_first)
 411                                 result = -1;    /* NULL "<" NOT_NULL */
 412                         else
 413                                 result = 1;             /* NULL ">" NOT_NULL */
 414                         break;
 415                 }
 416                 if (clause->risnull)
 417                 {
 418                         if (clause->nulls_first)
 419                                 result = 1;             /* NOT_NULL ">" NULL */
 420                         else
 421                                 result = -1;    /* NOT_NULL "<" NULL */
 422                         break;
 423                 }
 424
 425                 /*
 426                  * OK to call the comparison function.
 427                  */
 428                 InitFunctionCallInfoData(fcinfo, &(clause->cmpfinfo), 2,
 429                                                                  NULL, NULL);
 430                 fcinfo.arg[0] = clause->ldatum;
 431                 fcinfo.arg[1] = clause->rdatum;
 432                 fcinfo.argnull[0] = false;
 433                 fcinfo.argnull[1] = false;
 434                 fresult = FunctionCallInvoke(&fcinfo);
 435                 if (fcinfo.isnull)
 436                 {
 437                         nulleqnull = true;      /* treat like NULL = NULL */
 438                         continue;
 439                 }
 440                 result = DatumGetInt32(fresult);
 441
 442                 if (clause->reverse)
 443                         result = -result;
 444
 445                 if (result != 0)
 446                         break;
 447         }
 448
 449         /*
 450          * If we had any null comparison results or NULL-vs-NULL inputs, we do not
 451          * want to report that the tuples are equal.  Instead, if result is still
 452          * 0, change it to +1.  This will result in advancing the inner side of
 453          * the join.
 454          *
 455          * Likewise, if there was a constant-false joinqual, do not report
 456          * equality.  We have to check this as part of the mergequals, else the
 457          * rescan logic will do the wrong thing.
 458          */
 459         if (result == 0 &&
 460                 (nulleqnull || mergestate->mj_ConstFalseJoin))
 461                 result = 1;
 462
 463         MemoryContextSwitchTo(oldContext);
 464
 465         return result;
 466 }
 467
 468
 469 /*
 470  * Generate a fake join tuple with nulls for the inner tuple,
 471  * and return it if it passes the non-join quals.
 472  */
 473 static TupleTableSlot *
 474 MJFillOuter(MergeJoinState *node)
 475 {
 476         ExprContext *econtext = node->js.ps.ps_ExprContext;
 477         List       *otherqual = node->js.ps.qual;
 478
 479         ResetExprContext(econtext);
 480
 481         econtext->ecxt_outertuple = node->mj_OuterTupleSlot;
 482         econtext->ecxt_innertuple = node->mj_NullInnerTupleSlot;
 483
 484         if (ExecQual(otherqual, econtext, false))
 485         {
 486                 /*
 487                  * qualification succeeded.  now form the desired projection tuple and
 488                  * return the slot containing it.
 489                  */
 490                 TupleTableSlot *result;
 491                 ExprDoneCond isDone;
 492
 493                 MJ_printf("ExecMergeJoin: returning outer fill tuple\n");
 494
 495                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 496
 497                 if (isDone != ExprEndResult)
 498                 {
 499                         node->js.ps.ps_TupFromTlist =
 500                                 (isDone == ExprMultipleResult);
 501                         return result;
 502                 }
 503         }
 504
 505         return NULL;
 506 }
 507
 508 /*
 509  * Generate a fake join tuple with nulls for the outer tuple,
 510  * and return it if it passes the non-join quals.
 511  */
 512 static TupleTableSlot *
 513 MJFillInner(MergeJoinState *node)
 514 {
 515         ExprContext *econtext = node->js.ps.ps_ExprContext;
 516         List       *otherqual = node->js.ps.qual;
 517
 518         ResetExprContext(econtext);
 519
 520         econtext->ecxt_outertuple = node->mj_NullOuterTupleSlot;
 521         econtext->ecxt_innertuple = node->mj_InnerTupleSlot;
 522
 523         if (ExecQual(otherqual, econtext, false))
 524         {
 525                 /*
 526                  * qualification succeeded.  now form the desired projection tuple and
 527                  * return the slot containing it.
 528                  */
 529                 TupleTableSlot *result;
 530                 ExprDoneCond isDone;
 531
 532                 MJ_printf("ExecMergeJoin: returning inner fill tuple\n");
 533
 534                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 535
 536                 if (isDone != ExprEndResult)
 537                 {
 538                         node->js.ps.ps_TupFromTlist =
 539                                 (isDone == ExprMultipleResult);
 540                         return result;
 541                 }
 542         }
 543
 544         return NULL;
 545 }
 546
 547
 548 /*
 549  * Check that a qual condition is constant true or constant false.
 550  * If it is constant false (or null), set *is_const_false to TRUE.
 551  *
 552  * Constant true would normally be represented by a NIL list, but we allow an
 553  * actual bool Const as well.  We do expect that the planner will have thrown
 554  * away any non-constant terms that have been ANDed with a constant false.
 555  */
 556 static bool
 557 check_constant_qual(List *qual, bool *is_const_false)
 558 {
 559         ListCell   *lc;
 560
 561         foreach(lc, qual)
 562         {
 563                 Const      *con = (Const *) lfirst(lc);
 564
 565                 if (!con || !IsA(con, Const))
 566                         return false;
 567                 if (con->constisnull || !DatumGetBool(con->constvalue))
 568                         *is_const_false = true;
 569         }
 570         return true;
 571 }
 572
 573
 574 /* ----------------------------------------------------------------
 575  *              ExecMergeTupleDump
 576  *
 577  *              This function is called through the MJ_dump() macro
 578  *              when EXEC_MERGEJOINDEBUG is defined
 579  * ----------------------------------------------------------------
 580  */
 581 #ifdef EXEC_MERGEJOINDEBUG
 582
 583 static void
 584 ExecMergeTupleDumpOuter(MergeJoinState *mergestate)
 585 {
 586         TupleTableSlot *outerSlot = mergestate->mj_OuterTupleSlot;
 587
 588         printf("==== outer tuple ====\n");
 589         if (TupIsNull(outerSlot))
 590                 printf("(nil)\n");
 591         else
 592                 MJ_debugtup(outerSlot);
 593 }
 594
 595 static void
 596 ExecMergeTupleDumpInner(MergeJoinState *mergestate)
 597 {
 598         TupleTableSlot *innerSlot = mergestate->mj_InnerTupleSlot;
 599
 600         printf("==== inner tuple ====\n");
 601         if (TupIsNull(innerSlot))
 602                 printf("(nil)\n");
 603         else
 604                 MJ_debugtup(innerSlot);
 605 }
 606
 607 static void
 608 ExecMergeTupleDumpMarked(MergeJoinState *mergestate)
 609 {
 610         TupleTableSlot *markedSlot = mergestate->mj_MarkedTupleSlot;
 611
 612         printf("==== marked tuple ====\n");
 613         if (TupIsNull(markedSlot))
 614                 printf("(nil)\n");
 615         else
 616                 MJ_debugtup(markedSlot);
 617 }
 618
 619 static void
 620 ExecMergeTupleDump(MergeJoinState *mergestate)
 621 {
 622         printf("******** ExecMergeTupleDump ********\n");
 623
 624         ExecMergeTupleDumpOuter(mergestate);
 625         ExecMergeTupleDumpInner(mergestate);
 626         ExecMergeTupleDumpMarked(mergestate);
 627
 628         printf("******** \n");
 629 }
 630 #endif
 631
 632 /* ----------------------------------------------------------------
 633  *              ExecMergeJoin
 634  * ----------------------------------------------------------------
 635  */
 636 TupleTableSlot *
 637 ExecMergeJoin(MergeJoinState *node)
 638 {
 639         EState     *estate;
 640         List       *joinqual;
 641         List       *otherqual;
 642         bool            qualResult;
 643         int32           compareResult;
 644         PlanState  *innerPlan;
 645         TupleTableSlot *innerTupleSlot;
 646         PlanState  *outerPlan;
 647         TupleTableSlot *outerTupleSlot;
 648         ExprContext *econtext;
 649         bool            doFillOuter;
 650         bool            doFillInner;
 651
 652         /*
 653          * get information from node
 654          */
 655         estate = node->js.ps.state;
 656         innerPlan = innerPlanState(node);
 657         outerPlan = outerPlanState(node);
 658         econtext = node->js.ps.ps_ExprContext;
 659         joinqual = node->js.joinqual;
 660         otherqual = node->js.ps.qual;
 661         doFillOuter = node->mj_FillOuter;
 662         doFillInner = node->mj_FillInner;
 663
 664         /*
 665          * Check to see if we're still projecting out tuples from a previous join
 666          * tuple (because there is a function-returning-set in the projection
 667          * expressions).  If so, try to project another one.
 668          */
 669         if (node->js.ps.ps_TupFromTlist)
 670         {
 671                 TupleTableSlot *result;
 672                 ExprDoneCond isDone;
 673
 674                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 675                 if (isDone == ExprMultipleResult)
 676                         return result;
 677                 /* Done with that source tuple... */
 678                 node->js.ps.ps_TupFromTlist = false;
 679         }
 680
 681         /*
 682          * Reset per-tuple memory context to free any expression evaluation
 683          * storage allocated in the previous tuple cycle.  Note this can't happen
 684          * until we're done projecting out tuples from a join tuple.
 685          */
 686         ResetExprContext(econtext);
 687
 688         /*
 689          * ok, everything is setup.. let's go to work
 690          */
 691         for (;;)
 692         {
 693                 MJ_dump(node);
 694
 695                 /*
 696                  * get the current state of the join and do things accordingly.
 697                  */
 698                 switch (node->mj_JoinState)
 699                 {
 700                                 /*
 701                                  * EXEC_MJ_INITIALIZE_OUTER means that this is the first time
 702                                  * ExecMergeJoin() has been called and so we have to fetch the
 703                                  * first matchable tuple for both outer and inner subplans. We
 704                                  * do the outer side in INITIALIZE_OUTER state, then advance
 705                                  * to INITIALIZE_INNER state for the inner subplan.
 706                                  */
 707                         case EXEC_MJ_INITIALIZE_OUTER:
 708                                 MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_OUTER\n");
 709
 710                                 outerTupleSlot = ExecProcNode(outerPlan);
 711                                 node->mj_OuterTupleSlot = outerTupleSlot;
 712
 713                                 /* Compute join values and check for unmatchability */
 714                                 switch (MJEvalOuterValues(node))
 715                                 {
 716                                         case MJEVAL_MATCHABLE:
 717                                                 /* OK to go get the first inner tuple */
 718                                                 node->mj_JoinState = EXEC_MJ_INITIALIZE_INNER;
 719                                                 break;
 720                                         case MJEVAL_NONMATCHABLE:
 721                                                 /* Stay in same state to fetch next outer tuple */
 722                                                 if (doFillOuter)
 723                                                 {
 724                                                         /*
 725                                                          * Generate a fake join tuple with nulls for the
 726                                                          * inner tuple, and return it if it passes the
 727                                                          * non-join quals.
 728                                                          */
 729                                                         TupleTableSlot *result;
 730
 731                                                         result = MJFillOuter(node);
 732                                                         if (result)
 733                                                                 return result;
 734                                                 }
 735                                                 break;
 736                                         case MJEVAL_ENDOFJOIN:
 737                                                 /* No more outer tuples */
 738                                                 MJ_printf("ExecMergeJoin: nothing in outer subplan\n");
 739                                                 if (doFillInner)
 740                                                 {
 741                                                         /*
 742                                                          * Need to emit right-join tuples for remaining
 743                                                          * inner tuples. We set MatchedInner = true to
 744                                                          * force the ENDOUTER state to advance inner.
 745                                                          */
 746                                                         node->mj_JoinState = EXEC_MJ_ENDOUTER;
 747                                                         node->mj_MatchedInner = true;
 748                                                         break;
 749                                                 }
 750                                                 /* Otherwise we're done. */
 751                                                 return NULL;
 752                                 }
 753                                 break;
 754
 755                         case EXEC_MJ_INITIALIZE_INNER:
 756                                 MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_INNER\n");
 757
 758                                 innerTupleSlot = ExecProcNode(innerPlan);
 759                                 node->mj_InnerTupleSlot = innerTupleSlot;
 760
 761                                 /* Compute join values and check for unmatchability */
 762                                 switch (MJEvalInnerValues(node, innerTupleSlot))
 763                                 {
 764                                         case MJEVAL_MATCHABLE:
 765
 766                                                 /*
 767                                                  * OK, we have the initial tuples.      Begin by skipping
 768                                                  * non-matching tuples.
 769                                                  */
 770                                                 node->mj_JoinState = EXEC_MJ_SKIP_TEST;
 771                                                 break;
 772                                         case MJEVAL_NONMATCHABLE:
 773                                                 /* Mark before advancing, if wanted */
 774                                                 if (node->mj_ExtraMarks)
 775                                                         ExecMarkPos(innerPlan);
 776                                                 /* Stay in same state to fetch next inner tuple */
 777                                                 if (doFillInner)
 778                                                 {
 779                                                         /*
 780                                                          * Generate a fake join tuple with nulls for the
 781                                                          * outer tuple, and return it if it passes the
 782                                                          * non-join quals.
 783                                                          */
 784                                                         TupleTableSlot *result;
 785
 786                                                         result = MJFillInner(node);
 787                                                         if (result)
 788                                                                 return result;
 789                                                 }
 790                                                 break;
 791                                         case MJEVAL_ENDOFJOIN:
 792                                                 /* No more inner tuples */
 793                                                 MJ_printf("ExecMergeJoin: nothing in inner subplan\n");
 794                                                 if (doFillOuter)
 795                                                 {
 796                                                         /*
 797                                                          * Need to emit left-join tuples for all outer
 798                                                          * tuples, including the one we just fetched.  We
 799                                                          * set MatchedOuter = false to force the ENDINNER
 800                                                          * state to emit first tuple before advancing
 801                                                          * outer.
 802                                                          */
 803                                                         node->mj_JoinState = EXEC_MJ_ENDINNER;
 804                                                         node->mj_MatchedOuter = false;
 805                                                         break;
 806                                                 }
 807                                                 /* Otherwise we're done. */
 808                                                 return NULL;
 809                                 }
 810                                 break;
 811
 812                                 /*
 813                                  * EXEC_MJ_JOINTUPLES means we have two tuples which satisfied
 814                                  * the merge clause so we join them and then proceed to get
 815                                  * the next inner tuple (EXEC_MJ_NEXTINNER).
 816                                  */
 817                         case EXEC_MJ_JOINTUPLES:
 818                                 MJ_printf("ExecMergeJoin: EXEC_MJ_JOINTUPLES\n");
 819
 820                                 /*
 821                                  * Set the next state machine state.  The right things will
 822                                  * happen whether we return this join tuple or just fall
 823                                  * through to continue the state machine execution.
 824                                  */
 825                                 node->mj_JoinState = EXEC_MJ_NEXTINNER;
 826
 827                                 /*
 828                                  * Check the extra qual conditions to see if we actually want
 829                                  * to return this join tuple.  If not, can proceed with merge.
 830                                  * We must distinguish the additional joinquals (which must
 831                                  * pass to consider the tuples "matched" for outer-join logic)
 832                                  * from the otherquals (which must pass before we actually
 833                                  * return the tuple).
 834                                  *
 835                                  * We don't bother with a ResetExprContext here, on the
 836                                  * assumption that we just did one while checking the merge
 837                                  * qual.  One per tuple should be sufficient.  We do have to
 838                                  * set up the econtext links to the tuples for ExecQual to
 839                                  * use.
 840                                  */
 841                                 outerTupleSlot = node->mj_OuterTupleSlot;
 842                                 econtext->ecxt_outertuple = outerTupleSlot;
 843                                 innerTupleSlot = node->mj_InnerTupleSlot;
 844                                 econtext->ecxt_innertuple = innerTupleSlot;
 845
 846                                 qualResult = (joinqual == NIL ||
 847                                                           ExecQual(joinqual, econtext, false));
 848                                 MJ_DEBUG_QUAL(joinqual, qualResult);
 849
 850                                 if (qualResult)
 851                                 {
 852                                         node->mj_MatchedOuter = true;
 853                                         node->mj_MatchedInner = true;
 854
 855                                         /* In an antijoin, we never return a matched tuple */
 856                                         if (node->js.jointype == JOIN_ANTI)
 857                                         {
 858                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 859                                                 break;
 860                                         }
 861
 862                                         /*
 863                                          * In a semijoin, we'll consider returning the first
 864                                          * match, but after that we're done with this outer tuple.
 865                                          */
 866                                         if (node->js.jointype == JOIN_SEMI)
 867                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 868
 869                                         qualResult = (otherqual == NIL ||
 870                                                                   ExecQual(otherqual, econtext, false));
 871                                         MJ_DEBUG_QUAL(otherqual, qualResult);
 872
 873                                         if (qualResult)
 874                                         {
 875                                                 /*
 876                                                  * qualification succeeded.  now form the desired
 877                                                  * projection tuple and return the slot containing it.
 878                                                  */
 879                                                 TupleTableSlot *result;
 880                                                 ExprDoneCond isDone;
 881
 882                                                 MJ_printf("ExecMergeJoin: returning tuple\n");
 883
 884                                                 result = ExecProject(node->js.ps.ps_ProjInfo,
 885                                                                                          &isDone);
 886
 887                                                 if (isDone != ExprEndResult)
 888                                                 {
 889                                                         node->js.ps.ps_TupFromTlist =
 890                                                                 (isDone == ExprMultipleResult);
 891                                                         return result;
 892                                                 }
 893                                         }
 894                                 }
 895                                 break;
 896
 897                                 /*
 898                                  * EXEC_MJ_NEXTINNER means advance the inner scan to the next
 899                                  * tuple. If the tuple is not nil, we then proceed to test it
 900                                  * against the join qualification.
 901                                  *
 902                                  * Before advancing, we check to see if we must emit an
 903                                  * outer-join fill tuple for this inner tuple.
 904                                  */
 905                         case EXEC_MJ_NEXTINNER:
 906                                 MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTINNER\n");
 907
 908                                 if (doFillInner && !node->mj_MatchedInner)
 909                                 {
 910                                         /*
 911                                          * Generate a fake join tuple with nulls for the outer
 912                                          * tuple, and return it if it passes the non-join quals.
 913                                          */
 914                                         TupleTableSlot *result;
 915
 916                                         node->mj_MatchedInner = true;           /* do it only once */
 917
 918                                         result = MJFillInner(node);
 919                                         if (result)
 920                                                 return result;
 921                                 }
 922
 923                                 /*
 924                                  * now we get the next inner tuple, if any.  If there's none,
 925                                  * advance to next outer tuple (which may be able to join to
 926                                  * previously marked tuples).
 927                                  *
 928                                  * NB: must NOT do "extraMarks" here, since we may need to
 929                                  * return to previously marked tuples.
 930                                  */
 931                                 innerTupleSlot = ExecProcNode(innerPlan);
 932                                 node->mj_InnerTupleSlot = innerTupleSlot;
 933                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
 934                                 node->mj_MatchedInner = false;
 935
 936                                 /* Compute join values and check for unmatchability */
 937                                 switch (MJEvalInnerValues(node, innerTupleSlot))
 938                                 {
 939                                         case MJEVAL_MATCHABLE:
 940
 941                                                 /*
 942                                                  * Test the new inner tuple to see if it matches
 943                                                  * outer.
 944                                                  *
 945                                                  * If they do match, then we join them and move on to
 946                                                  * the next inner tuple (EXEC_MJ_JOINTUPLES).
 947                                                  *
 948                                                  * If they do not match then advance to next outer
 949                                                  * tuple.
 950                                                  */
 951                                                 compareResult = MJCompare(node);
 952                                                 MJ_DEBUG_COMPARE(compareResult);
 953
 954                                                 if (compareResult == 0)
 955                                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
 956                                                 else
 957                                                 {
 958                                                         Assert(compareResult < 0);
 959                                                         node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 960                                                 }
 961                                                 break;
 962                                         case MJEVAL_NONMATCHABLE:
 963
 964                                                 /*
 965                                                  * It contains a NULL and hence can't match any outer
 966                                                  * tuple, so we can skip the comparison and assume the
 967                                                  * new tuple is greater than current outer.
 968                                                  */
 969                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 970                                                 break;
 971                                         case MJEVAL_ENDOFJOIN:
 972
 973                                                 /*
 974                                                  * No more inner tuples.  However, this might be only
 975                                                  * effective and not physical end of inner plan, so
 976                                                  * force mj_InnerTupleSlot to null to make sure we
 977                                                  * don't fetch more inner tuples.  (We need this hack
 978                                                  * because we are not transiting to a state where the
 979                                                  * inner plan is assumed to be exhausted.)
 980                                                  */
 981                                                 node->mj_InnerTupleSlot = NULL;
 982                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 983                                                 break;
 984                                 }
 985                                 break;
 986
 987                                 /*-------------------------------------------
 988                                  * EXEC_MJ_NEXTOUTER means
 989                                  *
 990                                  *                              outer inner
 991                                  * outer tuple -  5             5  - marked tuple
 992                                  *                                5             5
 993                                  *                                6             6  - inner tuple
 994                                  *                                7             7
 995                                  *
 996                                  * we know we just bumped into the
 997                                  * first inner tuple > current outer tuple (or possibly
 998                                  * the end of the inner stream)
 999                                  * so get a new outer tuple and then
1000                                  * proceed to test it against the marked tuple
1001                                  * (EXEC_MJ_TESTOUTER)
1002                                  *
1003                                  * Before advancing, we check to see if we must emit an
1004                                  * outer-join fill tuple for this outer tuple.
1005                                  *------------------------------------------------
1006                                  */
1007                         case EXEC_MJ_NEXTOUTER:
1008                                 MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTOUTER\n");
1009
1010                                 if (doFillOuter && !node->mj_MatchedOuter)
1011                                 {
1012                                         /*
1013                                          * Generate a fake join tuple with nulls for the inner
1014                                          * tuple, and return it if it passes the non-join quals.
1015                                          */
1016                                         TupleTableSlot *result;
1017
1018                                         node->mj_MatchedOuter = true;           /* do it only once */
1019
1020                                         result = MJFillOuter(node);
1021                                         if (result)
1022                                                 return result;
1023                                 }
1024
1025                                 /*
1026                                  * now we get the next outer tuple, if any
1027                                  */
1028                                 outerTupleSlot = ExecProcNode(outerPlan);
1029                                 node->mj_OuterTupleSlot = outerTupleSlot;
1030                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
1031                                 node->mj_MatchedOuter = false;
1032
1033                                 /* Compute join values and check for unmatchability */
1034                                 switch (MJEvalOuterValues(node))
1035                                 {
1036                                         case MJEVAL_MATCHABLE:
1037                                                 /* Go test the new tuple against the marked tuple */
1038                                                 node->mj_JoinState = EXEC_MJ_TESTOUTER;
1039                                                 break;
1040                                         case MJEVAL_NONMATCHABLE:
1041                                                 /* Can't match, so fetch next outer tuple */
1042                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
1043                                                 break;
1044                                         case MJEVAL_ENDOFJOIN:
1045                                                 /* No more outer tuples */
1046                                                 MJ_printf("ExecMergeJoin: end of outer subplan\n");
1047                                                 innerTupleSlot = node->mj_InnerTupleSlot;
1048                                                 if (doFillInner && !TupIsNull(innerTupleSlot))
1049                                                 {
1050                                                         /*
1051                                                          * Need to emit right-join tuples for remaining
1052                                                          * inner tuples.
1053                                                          */
1054                                                         node->mj_JoinState = EXEC_MJ_ENDOUTER;
1055                                                         break;
1056                                                 }
1057                                                 /* Otherwise we're done. */
1058                                                 return NULL;
1059                                 }
1060                                 break;
1061
1062                                 /*--------------------------------------------------------
1063                                  * EXEC_MJ_TESTOUTER If the new outer tuple and the marked
1064                                  * tuple satisfy the merge clause then we know we have
1065                                  * duplicates in the outer scan so we have to restore the
1066                                  * inner scan to the marked tuple and proceed to join the
1067                                  * new outer tuple with the inner tuples.
1068                                  *
1069                                  * This is the case when
1070                                  *                                                outer inner
1071                                  *                                                      4         5  - marked tuple
1072                                  *                       outer tuple -  5         5
1073                                  *               new outer tuple -      5         5
1074                                  *                                                      6         8  - inner tuple
1075                                  *                                                      7        12
1076                                  *
1077                                  *                              new outer tuple == marked tuple
1078                                  *
1079                                  * If the outer tuple fails the test, then we are done
1080                                  * with the marked tuples, and we have to look for a
1081                                  * match to the current inner tuple.  So we will
1082                                  * proceed to skip outer tuples until outer >= inner
1083                                  * (EXEC_MJ_SKIP_TEST).
1084                                  *
1085                                  *              This is the case when
1086                                  *
1087                                  *                                                outer inner
1088                                  *                                                      5         5  - marked tuple
1089                                  *                       outer tuple -  5         5
1090                                  *               new outer tuple -      6         8  - inner tuple
1091                                  *                                                      7        12
1092                                  *
1093                                  *                              new outer tuple > marked tuple
1094                                  *
1095                                  *---------------------------------------------------------
1096                                  */
1097                         case EXEC_MJ_TESTOUTER:
1098                                 MJ_printf("ExecMergeJoin: EXEC_MJ_TESTOUTER\n");
1099
1100                                 /*
1101                                  * Here we must compare the outer tuple with the marked inner
1102                                  * tuple.  (We can ignore the result of MJEvalInnerValues,
1103                                  * since the marked inner tuple is certainly matchable.)
1104                                  */
1105                                 innerTupleSlot = node->mj_MarkedTupleSlot;
1106                                 (void) MJEvalInnerValues(node, innerTupleSlot);
1107
1108                                 compareResult = MJCompare(node);
1109                                 MJ_DEBUG_COMPARE(compareResult);
1110
1111                                 if (compareResult == 0)
1112                                 {
1113                                         /*
1114                                          * the merge clause matched so now we restore the inner
1115                                          * scan position to the first mark, and go join that tuple
1116                                          * (and any following ones) to the new outer.
1117                                          *
1118                                          * NOTE: we do not need to worry about the MatchedInner
1119                                          * state for the rescanned inner tuples.  We know all of
1120                                          * them will match this new outer tuple and therefore
1121                                          * won't be emitted as fill tuples.  This works *only*
1122                                          * because we require the extra joinquals to be constant
1123                                          * when doing a right or full join --- otherwise some of
1124                                          * the rescanned tuples might fail the extra joinquals.
1125                                          * This obviously won't happen for a constant-true extra
1126                                          * joinqual, while the constant-false case is handled by
1127                                          * forcing the merge clause to never match, so we never
1128                                          * get here.
1129                                          */
1130                                         ExecRestrPos(innerPlan);
1131
1132                                         /*
1133                                          * ExecRestrPos probably should give us back a new Slot,
1134                                          * but since it doesn't, use the marked slot.  (The
1135                                          * previously returned mj_InnerTupleSlot cannot be assumed
1136                                          * to hold the required tuple.)
1137                                          */
1138                                         node->mj_InnerTupleSlot = innerTupleSlot;
1139                                         /* we need not do MJEvalInnerValues again */
1140
1141                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
1142                                 }
1143                                 else
1144                                 {
1145                                         /* ----------------
1146                                          *      if the new outer tuple didn't match the marked inner
1147                                          *      tuple then we have a case like:
1148                                          *
1149                                          *                       outer inner
1150                                          *                         4     4      - marked tuple
1151                                          * new outer - 5         4
1152                                          *                         6     5      - inner tuple
1153                                          *                         7
1154                                          *
1155                                          *      which means that all subsequent outer tuples will be
1156                                          *      larger than our marked inner tuples.  So we need not
1157                                          *      revisit any of the marked tuples but can proceed to
1158                                          *      look for a match to the current inner.  If there's
1159                                          *      no more inners, no more matches are possible.
1160                                          * ----------------
1161                                          */
1162                                         Assert(compareResult > 0);
1163                                         innerTupleSlot = node->mj_InnerTupleSlot;
1164
1165                                         /* reload comparison data for current inner */
1166                                         switch (MJEvalInnerValues(node, innerTupleSlot))
1167                                         {
1168                                                 case MJEVAL_MATCHABLE:
1169                                                         /* proceed to compare it to the current outer */
1170                                                         node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1171                                                         break;
1172                                                 case MJEVAL_NONMATCHABLE:
1173
1174                                                         /*
1175                                                          * current inner can't possibly match any outer;
1176                                                          * better to advance the inner scan than the
1177                                                          * outer.
1178                                                          */
1179                                                         node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1180                                                         break;
1181                                                 case MJEVAL_ENDOFJOIN:
1182                                                         /* No more inner tuples */
1183                                                         if (doFillOuter)
1184                                                         {
1185                                                                 /*
1186                                                                  * Need to emit left-join tuples for remaining
1187                                                                  * outer tuples.
1188                                                                  */
1189                                                                 node->mj_JoinState = EXEC_MJ_ENDINNER;
1190                                                                 break;
1191                                                         }
1192                                                         /* Otherwise we're done. */
1193                                                         return NULL;
1194                                         }
1195                                 }
1196                                 break;
1197
1198                                 /*----------------------------------------------------------
1199                                  * EXEC_MJ_SKIP means compare tuples and if they do not
1200                                  * match, skip whichever is lesser.
1201                                  *
1202                                  * For example:
1203                                  *
1204                                  *                              outer inner
1205                                  *                                5             5
1206                                  *                                5             5
1207                                  * outer tuple -  6             8  - inner tuple
1208                                  *                                7    12
1209                                  *                                8    14
1210                                  *
1211                                  * we have to advance the outer scan
1212                                  * until we find the outer 8.
1213                                  *
1214                                  * On the other hand:
1215                                  *
1216                                  *                              outer inner
1217                                  *                                5             5
1218                                  *                                5             5
1219                                  * outer tuple - 12             8  - inner tuple
1220                                  *                               14    10
1221                                  *                               17    12
1222                                  *
1223                                  * we have to advance the inner scan
1224                                  * until we find the inner 12.
1225                                  *----------------------------------------------------------
1226                                  */
1227                         case EXEC_MJ_SKIP_TEST:
1228                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIP_TEST\n");
1229
1230                                 /*
1231                                  * before we advance, make sure the current tuples do not
1232                                  * satisfy the mergeclauses.  If they do, then we update the
1233                                  * marked tuple position and go join them.
1234                                  */
1235                                 compareResult = MJCompare(node);
1236                                 MJ_DEBUG_COMPARE(compareResult);
1237
1238                                 if (compareResult == 0)
1239                                 {
1240                                         ExecMarkPos(innerPlan);
1241
1242                                         MarkInnerTuple(node->mj_InnerTupleSlot, node);
1243
1244                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
1245                                 }
1246                                 else if (compareResult < 0)
1247                                         node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE;
1248                                 else
1249                                         /* compareResult > 0 */
1250                                         node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1251                                 break;
1252
1253                                 /*
1254                                  * SKIPOUTER_ADVANCE: advance over an outer tuple that is
1255                                  * known not to join to any inner tuple.
1256                                  *
1257                                  * Before advancing, we check to see if we must emit an
1258                                  * outer-join fill tuple for this outer tuple.
1259                                  */
1260                         case EXEC_MJ_SKIPOUTER_ADVANCE:
1261                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPOUTER_ADVANCE\n");
1262
1263                                 if (doFillOuter && !node->mj_MatchedOuter)
1264                                 {
1265                                         /*
1266                                          * Generate a fake join tuple with nulls for the inner
1267                                          * tuple, and return it if it passes the non-join quals.
1268                                          */
1269                                         TupleTableSlot *result;
1270
1271                                         node->mj_MatchedOuter = true;           /* do it only once */
1272
1273                                         result = MJFillOuter(node);
1274                                         if (result)
1275                                                 return result;
1276                                 }
1277
1278                                 /*
1279                                  * now we get the next outer tuple, if any
1280                                  */
1281                                 outerTupleSlot = ExecProcNode(outerPlan);
1282                                 node->mj_OuterTupleSlot = outerTupleSlot;
1283                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
1284                                 node->mj_MatchedOuter = false;
1285
1286                                 /* Compute join values and check for unmatchability */
1287                                 switch (MJEvalOuterValues(node))
1288                                 {
1289                                         case MJEVAL_MATCHABLE:
1290                                                 /* Go test the new tuple against the current inner */
1291                                                 node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1292                                                 break;
1293                                         case MJEVAL_NONMATCHABLE:
1294                                                 /* Can't match, so fetch next outer tuple */
1295                                                 node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE;
1296                                                 break;
1297                                         case MJEVAL_ENDOFJOIN:
1298                                                 /* No more outer tuples */
1299                                                 MJ_printf("ExecMergeJoin: end of outer subplan\n");
1300                                                 innerTupleSlot = node->mj_InnerTupleSlot;
1301                                                 if (doFillInner && !TupIsNull(innerTupleSlot))
1302                                                 {
1303                                                         /*
1304                                                          * Need to emit right-join tuples for remaining
1305                                                          * inner tuples.
1306                                                          */
1307                                                         node->mj_JoinState = EXEC_MJ_ENDOUTER;
1308                                                         break;
1309                                                 }
1310                                                 /* Otherwise we're done. */
1311                                                 return NULL;
1312                                 }
1313                                 break;
1314
1315                                 /*
1316                                  * SKIPINNER_ADVANCE: advance over an inner tuple that is
1317                                  * known not to join to any outer tuple.
1318                                  *
1319                                  * Before advancing, we check to see if we must emit an
1320                                  * outer-join fill tuple for this inner tuple.
1321                                  */
1322                         case EXEC_MJ_SKIPINNER_ADVANCE:
1323                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPINNER_ADVANCE\n");
1324
1325                                 if (doFillInner && !node->mj_MatchedInner)
1326                                 {
1327                                         /*
1328                                          * Generate a fake join tuple with nulls for the outer
1329                                          * tuple, and return it if it passes the non-join quals.
1330                                          */
1331                                         TupleTableSlot *result;
1332
1333                                         node->mj_MatchedInner = true;           /* do it only once */
1334
1335                                         result = MJFillInner(node);
1336                                         if (result)
1337                                                 return result;
1338                                 }
1339
1340                                 /* Mark before advancing, if wanted */
1341                                 if (node->mj_ExtraMarks)
1342                                         ExecMarkPos(innerPlan);
1343
1344                                 /*
1345                                  * now we get the next inner tuple, if any
1346                                  */
1347                                 innerTupleSlot = ExecProcNode(innerPlan);
1348                                 node->mj_InnerTupleSlot = innerTupleSlot;
1349                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
1350                                 node->mj_MatchedInner = false;
1351
1352                                 /* Compute join values and check for unmatchability */
1353                                 switch (MJEvalInnerValues(node, innerTupleSlot))
1354                                 {
1355                                         case MJEVAL_MATCHABLE:
1356                                                 /* proceed to compare it to the current outer */
1357                                                 node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1358                                                 break;
1359                                         case MJEVAL_NONMATCHABLE:
1360
1361                                                 /*
1362                                                  * current inner can't possibly match any outer;
1363                                                  * better to advance the inner scan than the outer.
1364                                                  */
1365                                                 node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1366                                                 break;
1367                                         case MJEVAL_ENDOFJOIN:
1368                                                 /* No more inner tuples */
1369                                                 MJ_printf("ExecMergeJoin: end of inner subplan\n");
1370                                                 outerTupleSlot = node->mj_OuterTupleSlot;
1371                                                 if (doFillOuter && !TupIsNull(outerTupleSlot))
1372                                                 {
1373                                                         /*
1374                                                          * Need to emit left-join tuples for remaining
1375                                                          * outer tuples.
1376                                                          */
1377                                                         node->mj_JoinState = EXEC_MJ_ENDINNER;
1378                                                         break;
1379                                                 }
1380                                                 /* Otherwise we're done. */
1381                                                 return NULL;
1382                                 }
1383                                 break;
1384
1385                                 /*
1386                                  * EXEC_MJ_ENDOUTER means we have run out of outer tuples, but
1387                                  * are doing a right/full join and therefore must null-fill
1388                                  * any remaing unmatched inner tuples.
1389                                  */
1390                         case EXEC_MJ_ENDOUTER:
1391                                 MJ_printf("ExecMergeJoin: EXEC_MJ_ENDOUTER\n");
1392
1393                                 Assert(doFillInner);
1394
1395                                 if (!node->mj_MatchedInner)
1396                                 {
1397                                         /*
1398                                          * Generate a fake join tuple with nulls for the outer
1399                                          * tuple, and return it if it passes the non-join quals.
1400                                          */
1401                                         TupleTableSlot *result;
1402
1403                                         node->mj_MatchedInner = true;           /* do it only once */
1404
1405                                         result = MJFillInner(node);
1406                                         if (result)
1407                                                 return result;
1408                                 }
1409
1410                                 /* Mark before advancing, if wanted */
1411                                 if (node->mj_ExtraMarks)
1412                                         ExecMarkPos(innerPlan);
1413
1414                                 /*
1415                                  * now we get the next inner tuple, if any
1416                                  */
1417                                 innerTupleSlot = ExecProcNode(innerPlan);
1418                                 node->mj_InnerTupleSlot = innerTupleSlot;
1419                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
1420                                 node->mj_MatchedInner = false;
1421
1422                                 if (TupIsNull(innerTupleSlot))
1423                                 {
1424                                         MJ_printf("ExecMergeJoin: end of inner subplan\n");
1425                                         return NULL;
1426                                 }
1427
1428                                 /* Else remain in ENDOUTER state and process next tuple. */
1429                                 break;
1430
1431                                 /*
1432                                  * EXEC_MJ_ENDINNER means we have run out of inner tuples, but
1433                                  * are doing a left/full join and therefore must null- fill
1434                                  * any remaing unmatched outer tuples.
1435                                  */
1436                         case EXEC_MJ_ENDINNER:
1437                                 MJ_printf("ExecMergeJoin: EXEC_MJ_ENDINNER\n");
1438
1439                                 Assert(doFillOuter);
1440
1441                                 if (!node->mj_MatchedOuter)
1442                                 {
1443                                         /*
1444                                          * Generate a fake join tuple with nulls for the inner
1445                                          * tuple, and return it if it passes the non-join quals.
1446                                          */
1447                                         TupleTableSlot *result;
1448
1449                                         node->mj_MatchedOuter = true;           /* do it only once */
1450
1451                                         result = MJFillOuter(node);
1452                                         if (result)
1453                                                 return result;
1454                                 }
1455
1456                                 /*
1457                                  * now we get the next outer tuple, if any
1458                                  */
1459                                 outerTupleSlot = ExecProcNode(outerPlan);
1460                                 node->mj_OuterTupleSlot = outerTupleSlot;
1461                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
1462                                 node->mj_MatchedOuter = false;
1463
1464                                 if (TupIsNull(outerTupleSlot))
1465                                 {
1466                                         MJ_printf("ExecMergeJoin: end of outer subplan\n");
1467                                         return NULL;
1468                                 }
1469
1470                                 /* Else remain in ENDINNER state and process next tuple. */
1471                                 break;
1472
1473                                 /*
1474                                  * broken state value?
1475                                  */
1476                         default:
1477                                 elog(ERROR, "unrecognized mergejoin state: %d",
1478                                          (int) node->mj_JoinState);
1479                 }
1480         }
1481 }
1482
1483 /* ----------------------------------------------------------------
1484  *              ExecInitMergeJoin
1485  * ----------------------------------------------------------------
1486  */
1487 MergeJoinState *
1488 ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
1489 {
1490         MergeJoinState *mergestate;
1491
1492         /* check for unsupported flags */
1493         Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
1494
1495         MJ1_printf("ExecInitMergeJoin: %s\n",
1496                            "initializing node");
1497
1498         /*
1499          * create state structure
1500          */
1501         mergestate = makeNode(MergeJoinState);
1502         mergestate->js.ps.plan = (Plan *) node;
1503         mergestate->js.ps.state = estate;
1504
1505         /*
1506          * Miscellaneous initialization
1507          *
1508          * create expression context for node
1509          */
1510         ExecAssignExprContext(estate, &mergestate->js.ps);
1511
1512         /*
1513          * we need two additional econtexts in which we can compute the join
1514          * expressions from the left and right input tuples.  The node's regular
1515          * econtext won't do because it gets reset too often.
1516          */
1517         mergestate->mj_OuterEContext = CreateExprContext(estate);
1518         mergestate->mj_InnerEContext = CreateExprContext(estate);
1519
1520         /*
1521          * initialize child expressions
1522          */
1523         mergestate->js.ps.targetlist = (List *)
1524                 ExecInitExpr((Expr *) node->join.plan.targetlist,
1525                                          (PlanState *) mergestate);
1526         mergestate->js.ps.qual = (List *)
1527                 ExecInitExpr((Expr *) node->join.plan.qual,
1528                                          (PlanState *) mergestate);
1529         mergestate->js.jointype = node->join.jointype;
1530         mergestate->js.joinqual = (List *)
1531                 ExecInitExpr((Expr *) node->join.joinqual,
1532                                          (PlanState *) mergestate);
1533         mergestate->mj_ConstFalseJoin = false;
1534         /* mergeclauses are handled below */
1535
1536         /*
1537          * initialize child nodes
1538          *
1539          * inner child must support MARK/RESTORE.
1540          */
1541         outerPlanState(mergestate) = ExecInitNode(outerPlan(node), estate, eflags);
1542         innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate,
1543                                                                                           eflags | EXEC_FLAG_MARK);
1544
1545         /*
1546          * For certain types of inner child nodes, it is advantageous to issue
1547          * MARK every time we advance past an inner tuple we will never return to.
1548          * For other types, MARK on a tuple we cannot return to is a waste of
1549          * cycles.      Detect which case applies and set mj_ExtraMarks if we want to
1550          * issue "unnecessary" MARK calls.
1551          *
1552          * Currently, only Material wants the extra MARKs, and it will be helpful
1553          * only if eflags doesn't specify REWIND.
1554          */
1555         if (IsA(innerPlan(node), Material) &&
1556                 (eflags & EXEC_FLAG_REWIND) == 0)
1557                 mergestate->mj_ExtraMarks = true;
1558         else
1559                 mergestate->mj_ExtraMarks = false;
1560
1561         /*
1562          * tuple table initialization
1563          */
1564         ExecInitResultTupleSlot(estate, &mergestate->js.ps);
1565
1566         mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate);
1567         ExecSetSlotDescriptor(mergestate->mj_MarkedTupleSlot,
1568                                                   ExecGetResultType(innerPlanState(mergestate)));
1569
1570         switch (node->join.jointype)
1571         {
1572                 case JOIN_INNER:
1573                 case JOIN_SEMI:
1574                         mergestate->mj_FillOuter = false;
1575                         mergestate->mj_FillInner = false;
1576                         break;
1577                 case JOIN_LEFT:
1578                 case JOIN_ANTI:
1579                         mergestate->mj_FillOuter = true;
1580                         mergestate->mj_FillInner = false;
1581                         mergestate->mj_NullInnerTupleSlot =
1582                                 ExecInitNullTupleSlot(estate,
1583                                                           ExecGetResultType(innerPlanState(mergestate)));
1584                         break;
1585                 case JOIN_RIGHT:
1586                         mergestate->mj_FillOuter = false;
1587                         mergestate->mj_FillInner = true;
1588                         mergestate->mj_NullOuterTupleSlot =
1589                                 ExecInitNullTupleSlot(estate,
1590                                                           ExecGetResultType(outerPlanState(mergestate)));
1591
1592                         /*
1593                          * Can't handle right or full join with non-constant extra
1594                          * joinclauses.  This should have been caught by planner.
1595                          */
1596                         if (!check_constant_qual(node->join.joinqual,
1597                                                                          &mergestate->mj_ConstFalseJoin))
1598                                 ereport(ERROR,
1599                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1600                                                  errmsg("RIGHT JOIN is only supported with merge-joinable join conditions")));
1601                         break;
1602                 case JOIN_FULL:
1603                         mergestate->mj_FillOuter = true;
1604                         mergestate->mj_FillInner = true;
1605                         mergestate->mj_NullOuterTupleSlot =
1606                                 ExecInitNullTupleSlot(estate,
1607                                                           ExecGetResultType(outerPlanState(mergestate)));
1608                         mergestate->mj_NullInnerTupleSlot =
1609                                 ExecInitNullTupleSlot(estate,
1610                                                           ExecGetResultType(innerPlanState(mergestate)));
1611
1612                         /*
1613                          * Can't handle right or full join with non-constant extra
1614                          * joinclauses.  This should have been caught by planner.
1615                          */
1616                         if (!check_constant_qual(node->join.joinqual,
1617                                                                          &mergestate->mj_ConstFalseJoin))
1618                                 ereport(ERROR,
1619                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1620                                                  errmsg("FULL JOIN is only supported with merge-joinable join conditions")));
1621                         break;
1622                 default:
1623                         elog(ERROR, "unrecognized join type: %d",
1624                                  (int) node->join.jointype);
1625         }
1626
1627         /*
1628          * initialize tuple type and projection info
1629          */
1630         ExecAssignResultTypeFromTL(&mergestate->js.ps);
1631         ExecAssignProjectionInfo(&mergestate->js.ps, NULL);
1632
1633         /*
1634          * preprocess the merge clauses
1635          */
1636         mergestate->mj_NumClauses = list_length(node->mergeclauses);
1637         mergestate->mj_Clauses = MJExamineQuals(node->mergeclauses,
1638                                                                                         node->mergeFamilies,
1639                                                                                         node->mergeStrategies,
1640                                                                                         node->mergeNullsFirst,
1641                                                                                         (PlanState *) mergestate);
1642
1643         /*
1644          * initialize join state
1645          */
1646         mergestate->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER;
1647         mergestate->js.ps.ps_TupFromTlist = false;
1648         mergestate->mj_MatchedOuter = false;
1649         mergestate->mj_MatchedInner = false;
1650         mergestate->mj_OuterTupleSlot = NULL;
1651         mergestate->mj_InnerTupleSlot = NULL;
1652
1653         /*
1654          * initialization successful
1655          */
1656         MJ1_printf("ExecInitMergeJoin: %s\n",
1657                            "node initialized");
1658
1659         return mergestate;
1660 }
1661
1662 /* ----------------------------------------------------------------
1663  *              ExecEndMergeJoin
1664  *
1665  * old comments
1666  *              frees storage allocated through C routines.
1667  * ----------------------------------------------------------------
1668  */
1669 void
1670 ExecEndMergeJoin(MergeJoinState *node)
1671 {
1672         MJ1_printf("ExecEndMergeJoin: %s\n",
1673                            "ending node processing");
1674
1675         /*
1676          * Free the exprcontext
1677          */
1678         ExecFreeExprContext(&node->js.ps);
1679
1680         /*
1681          * clean out the tuple table
1682          */
1683         ExecClearTuple(node->js.ps.ps_ResultTupleSlot);
1684         ExecClearTuple(node->mj_MarkedTupleSlot);
1685
1686         /*
1687          * shut down the subplans
1688          */
1689         ExecEndNode(innerPlanState(node));
1690         ExecEndNode(outerPlanState(node));
1691
1692         MJ1_printf("ExecEndMergeJoin: %s\n",
1693                            "node processing ended");
1694 }
1695
1696 void
1697 ExecReScanMergeJoin(MergeJoinState *node)
1698 {
1699         ExecClearTuple(node->mj_MarkedTupleSlot);
1700
1701         node->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER;
1702         node->js.ps.ps_TupFromTlist = false;
1703         node->mj_MatchedOuter = false;
1704         node->mj_MatchedInner = false;
1705         node->mj_OuterTupleSlot = NULL;
1706         node->mj_InnerTupleSlot = NULL;
1707
1708         /*
1709          * if chgParam of subnodes is not null then plans will be re-scanned by
1710          * first ExecProcNode.
1711          */
1712         if (node->js.ps.lefttree->chgParam == NULL)
1713                 ExecReScan(node->js.ps.lefttree);
1714         if (node->js.ps.righttree->chgParam == NULL)
1715                 ExecReScan(node->js.ps.righttree);
1716
1717 }