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) 1996-2008, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/executor/nodeMergejoin.c,v 1.93 2008/08/15 19:20:42 tgl Exp $
  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/execdefs.h"
  99 #include "executor/nodeMergejoin.h"
 100 #include "miscadmin.h"
 101 #include "utils/acl.h"
 102 #include "utils/lsyscache.h"
 103 #include "utils/memutils.h"
 104 #include "utils/syscache.h"
 105
 106
 107 /*
 108  * Runtime data for each mergejoin clause
 109  */
 110 typedef struct MergeJoinClauseData
 111 {
 112         /* Executable expression trees */
 113         ExprState  *lexpr;                      /* left-hand (outer) input expression */
 114         ExprState  *rexpr;                      /* right-hand (inner) input expression */
 115
 116         /*
 117          * If we have a current left or right input tuple, the values of the
 118          * expressions are loaded into these fields:
 119          */
 120         Datum           ldatum;                 /* current left-hand value */
 121         Datum           rdatum;                 /* current right-hand value */
 122         bool            lisnull;                /* and their isnull flags */
 123         bool            risnull;
 124
 125         /*
 126          * The comparison strategy in use, and the lookup info to let us call the
 127          * btree comparison support function.
 128          */
 129         bool            reverse;                /* if true, negate the cmpfn's output */
 130         bool            nulls_first;    /* if true, nulls sort low */
 131         FmgrInfo        cmpfinfo;
 132 } MergeJoinClauseData;
 133
 134
 135 #define MarkInnerTuple(innerTupleSlot, mergestate) \
 136         ExecCopySlot((mergestate)->mj_MarkedTupleSlot, (innerTupleSlot))
 137
 138
 139 /*
 140  * MJExamineQuals
 141  *
 142  * This deconstructs the list of mergejoinable expressions, which is given
 143  * to us by the planner in the form of a list of "leftexpr = rightexpr"
 144  * expression trees in the order matching the sort columns of the inputs.
 145  * We build an array of MergeJoinClause structs containing the information
 146  * we will need at runtime.  Each struct essentially tells us how to compare
 147  * the two expressions from the original clause.
 148  *
 149  * In addition to the expressions themselves, the planner passes the btree
 150  * opfamily OID, btree strategy number (BTLessStrategyNumber or
 151  * BTGreaterStrategyNumber), and nulls-first flag that identify the intended
 152  * sort ordering for each merge key.  The mergejoinable operator is an
 153  * equality operator in this opfamily, and the two inputs are guaranteed to be
 154  * ordered in either increasing or decreasing (respectively) order according
 155  * to this opfamily, with nulls at the indicated end of the range.      This
 156  * allows us to obtain the needed comparison function from the opfamily.
 157  */
 158 static MergeJoinClause
 159 MJExamineQuals(List *mergeclauses,
 160                            Oid *mergefamilies,
 161                            int *mergestrategies,
 162                            bool *mergenullsfirst,
 163                            PlanState *parent)
 164 {
 165         MergeJoinClause clauses;
 166         int                     nClauses = list_length(mergeclauses);
 167         int                     iClause;
 168         ListCell   *cl;
 169
 170         clauses = (MergeJoinClause) palloc0(nClauses * sizeof(MergeJoinClauseData));
 171
 172         iClause = 0;
 173         foreach(cl, mergeclauses)
 174         {
 175                 OpExpr     *qual = (OpExpr *) lfirst(cl);
 176                 MergeJoinClause clause = &clauses[iClause];
 177                 Oid                     opfamily = mergefamilies[iClause];
 178                 StrategyNumber opstrategy = mergestrategies[iClause];
 179                 bool            nulls_first = mergenullsfirst[iClause];
 180                 int                     op_strategy;
 181                 Oid                     op_lefttype;
 182                 Oid                     op_righttype;
 183                 RegProcedure cmpproc;
 184                 AclResult       aclresult;
 185
 186                 if (!IsA(qual, OpExpr))
 187                         elog(ERROR, "mergejoin clause is not an OpExpr");
 188
 189                 /*
 190                  * Prepare the input expressions for execution.
 191                  */
 192                 clause->lexpr = ExecInitExpr((Expr *) linitial(qual->args), parent);
 193                 clause->rexpr = ExecInitExpr((Expr *) lsecond(qual->args), parent);
 194
 195                 /* Extract the operator's declared left/right datatypes */
 196                 get_op_opfamily_properties(qual->opno, opfamily,
 197                                                                    &op_strategy,
 198                                                                    &op_lefttype,
 199                                                                    &op_righttype);
 200                 if (op_strategy != BTEqualStrategyNumber)               /* should not happen */
 201                         elog(ERROR, "cannot merge using non-equality operator %u",
 202                                  qual->opno);
 203
 204                 /* And get the matching support procedure (comparison function) */
 205                 cmpproc = get_opfamily_proc(opfamily,
 206                                                                         op_lefttype,
 207                                                                         op_righttype,
 208                                                                         BTORDER_PROC);
 209                 if (!RegProcedureIsValid(cmpproc))              /* should not happen */
 210                         elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
 211                                  BTORDER_PROC, op_lefttype, op_righttype, opfamily);
 212
 213                 /* Check permission to call cmp function */
 214                 aclresult = pg_proc_aclcheck(cmpproc, GetUserId(), ACL_EXECUTE);
 215                 if (aclresult != ACLCHECK_OK)
 216                         aclcheck_error(aclresult, ACL_KIND_PROC,
 217                                                    get_func_name(cmpproc));
 218
 219                 /* Set up the fmgr lookup information */
 220                 fmgr_info(cmpproc, &(clause->cmpfinfo));
 221
 222                 /* Fill the additional comparison-strategy flags */
 223                 if (opstrategy == BTLessStrategyNumber)
 224                         clause->reverse = false;
 225                 else if (opstrategy == BTGreaterStrategyNumber)
 226                         clause->reverse = true;
 227                 else    /* planner screwed up */
 228                         elog(ERROR, "unsupported mergejoin strategy %d", opstrategy);
 229
 230                 clause->nulls_first = nulls_first;
 231
 232                 iClause++;
 233         }
 234
 235         return clauses;
 236 }
 237
 238 /*
 239  * MJEvalOuterValues
 240  *
 241  * Compute the values of the mergejoined expressions for the current
 242  * outer tuple.  We also detect whether it's impossible for the current
 243  * outer tuple to match anything --- this is true if it yields a NULL
 244  * input, since we assume mergejoin operators are strict.
 245  *
 246  * We evaluate the values in OuterEContext, which can be reset each
 247  * time we move to a new tuple.
 248  */
 249 static bool
 250 MJEvalOuterValues(MergeJoinState *mergestate)
 251 {
 252         ExprContext *econtext = mergestate->mj_OuterEContext;
 253         bool            canmatch = true;
 254         int                     i;
 255         MemoryContext oldContext;
 256
 257         ResetExprContext(econtext);
 258
 259         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 260
 261         econtext->ecxt_outertuple = mergestate->mj_OuterTupleSlot;
 262
 263         for (i = 0; i < mergestate->mj_NumClauses; i++)
 264         {
 265                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 266
 267                 clause->ldatum = ExecEvalExpr(clause->lexpr, econtext,
 268                                                                           &clause->lisnull, NULL);
 269                 if (clause->lisnull)
 270                         canmatch = false;
 271         }
 272
 273         MemoryContextSwitchTo(oldContext);
 274
 275         return canmatch;
 276 }
 277
 278 /*
 279  * MJEvalInnerValues
 280  *
 281  * Same as above, but for the inner tuple.      Here, we have to be prepared
 282  * to load data from either the true current inner, or the marked inner,
 283  * so caller must tell us which slot to load from.
 284  */
 285 static bool
 286 MJEvalInnerValues(MergeJoinState *mergestate, TupleTableSlot *innerslot)
 287 {
 288         ExprContext *econtext = mergestate->mj_InnerEContext;
 289         bool            canmatch = true;
 290         int                     i;
 291         MemoryContext oldContext;
 292
 293         ResetExprContext(econtext);
 294
 295         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 296
 297         econtext->ecxt_innertuple = innerslot;
 298
 299         for (i = 0; i < mergestate->mj_NumClauses; i++)
 300         {
 301                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 302
 303                 clause->rdatum = ExecEvalExpr(clause->rexpr, econtext,
 304                                                                           &clause->risnull, NULL);
 305                 if (clause->risnull)
 306                         canmatch = false;
 307         }
 308
 309         MemoryContextSwitchTo(oldContext);
 310
 311         return canmatch;
 312 }
 313
 314 /*
 315  * MJCompare
 316  *
 317  * Compare the mergejoinable values of the current two input tuples
 318  * and return 0 if they are equal (ie, the mergejoin equalities all
 319  * succeed), +1 if outer > inner, -1 if outer < inner.
 320  *
 321  * MJEvalOuterValues and MJEvalInnerValues must already have been called
 322  * for the current outer and inner tuples, respectively.
 323  */
 324 static int32
 325 MJCompare(MergeJoinState *mergestate)
 326 {
 327         int32           result = 0;
 328         bool            nulleqnull = false;
 329         ExprContext *econtext = mergestate->js.ps.ps_ExprContext;
 330         int                     i;
 331         MemoryContext oldContext;
 332         FunctionCallInfoData fcinfo;
 333
 334         /*
 335          * Call the comparison functions in short-lived context, in case they leak
 336          * memory.
 337          */
 338         ResetExprContext(econtext);
 339
 340         oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
 341
 342         for (i = 0; i < mergestate->mj_NumClauses; i++)
 343         {
 344                 MergeJoinClause clause = &mergestate->mj_Clauses[i];
 345                 Datum           fresult;
 346
 347                 /*
 348                  * Deal with null inputs.
 349                  */
 350                 if (clause->lisnull)
 351                 {
 352                         if (clause->risnull)
 353                         {
 354                                 nulleqnull = true;              /* NULL "=" NULL */
 355                                 continue;
 356                         }
 357                         if (clause->nulls_first)
 358                                 result = -1;    /* NULL "<" NOT_NULL */
 359                         else
 360                                 result = 1;             /* NULL ">" NOT_NULL */
 361                         break;
 362                 }
 363                 if (clause->risnull)
 364                 {
 365                         if (clause->nulls_first)
 366                                 result = 1;             /* NOT_NULL ">" NULL */
 367                         else
 368                                 result = -1;    /* NOT_NULL "<" NULL */
 369                         break;
 370                 }
 371
 372                 /*
 373                  * OK to call the comparison function.
 374                  */
 375                 InitFunctionCallInfoData(fcinfo, &(clause->cmpfinfo), 2,
 376                                                                  NULL, NULL);
 377                 fcinfo.arg[0] = clause->ldatum;
 378                 fcinfo.arg[1] = clause->rdatum;
 379                 fcinfo.argnull[0] = false;
 380                 fcinfo.argnull[1] = false;
 381                 fresult = FunctionCallInvoke(&fcinfo);
 382                 if (fcinfo.isnull)
 383                 {
 384                         nulleqnull = true;      /* treat like NULL = NULL */
 385                         continue;
 386                 }
 387                 result = DatumGetInt32(fresult);
 388
 389                 if (clause->reverse)
 390                         result = -result;
 391
 392                 if (result != 0)
 393                         break;
 394         }
 395
 396         /*
 397          * If we had any null comparison results or NULL-vs-NULL inputs, we do not
 398          * want to report that the tuples are equal.  Instead, if result is still
 399          * 0, change it to +1.  This will result in advancing the inner side of
 400          * the join.
 401          */
 402         if (nulleqnull && result == 0)
 403                 result = 1;
 404
 405         MemoryContextSwitchTo(oldContext);
 406
 407         return result;
 408 }
 409
 410
 411 /*
 412  * Generate a fake join tuple with nulls for the inner tuple,
 413  * and return it if it passes the non-join quals.
 414  */
 415 static TupleTableSlot *
 416 MJFillOuter(MergeJoinState *node)
 417 {
 418         ExprContext *econtext = node->js.ps.ps_ExprContext;
 419         List       *otherqual = node->js.ps.qual;
 420
 421         ResetExprContext(econtext);
 422
 423         econtext->ecxt_outertuple = node->mj_OuterTupleSlot;
 424         econtext->ecxt_innertuple = node->mj_NullInnerTupleSlot;
 425
 426         if (ExecQual(otherqual, econtext, false))
 427         {
 428                 /*
 429                  * qualification succeeded.  now form the desired projection tuple and
 430                  * return the slot containing it.
 431                  */
 432                 TupleTableSlot *result;
 433                 ExprDoneCond isDone;
 434
 435                 MJ_printf("ExecMergeJoin: returning outer fill tuple\n");
 436
 437                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 438
 439                 if (isDone != ExprEndResult)
 440                 {
 441                         node->js.ps.ps_TupFromTlist =
 442                                 (isDone == ExprMultipleResult);
 443                         return result;
 444                 }
 445         }
 446
 447         return NULL;
 448 }
 449
 450 /*
 451  * Generate a fake join tuple with nulls for the outer tuple,
 452  * and return it if it passes the non-join quals.
 453  */
 454 static TupleTableSlot *
 455 MJFillInner(MergeJoinState *node)
 456 {
 457         ExprContext *econtext = node->js.ps.ps_ExprContext;
 458         List       *otherqual = node->js.ps.qual;
 459
 460         ResetExprContext(econtext);
 461
 462         econtext->ecxt_outertuple = node->mj_NullOuterTupleSlot;
 463         econtext->ecxt_innertuple = node->mj_InnerTupleSlot;
 464
 465         if (ExecQual(otherqual, econtext, false))
 466         {
 467                 /*
 468                  * qualification succeeded.  now form the desired projection tuple and
 469                  * return the slot containing it.
 470                  */
 471                 TupleTableSlot *result;
 472                 ExprDoneCond isDone;
 473
 474                 MJ_printf("ExecMergeJoin: returning inner fill tuple\n");
 475
 476                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 477
 478                 if (isDone != ExprEndResult)
 479                 {
 480                         node->js.ps.ps_TupFromTlist =
 481                                 (isDone == ExprMultipleResult);
 482                         return result;
 483                 }
 484         }
 485
 486         return NULL;
 487 }
 488
 489
 490 /* ----------------------------------------------------------------
 491  *              ExecMergeTupleDump
 492  *
 493  *              This function is called through the MJ_dump() macro
 494  *              when EXEC_MERGEJOINDEBUG is defined
 495  * ----------------------------------------------------------------
 496  */
 497 #ifdef EXEC_MERGEJOINDEBUG
 498
 499 static void
 500 ExecMergeTupleDumpOuter(MergeJoinState *mergestate)
 501 {
 502         TupleTableSlot *outerSlot = mergestate->mj_OuterTupleSlot;
 503
 504         printf("==== outer tuple ====\n");
 505         if (TupIsNull(outerSlot))
 506                 printf("(nil)\n");
 507         else
 508                 MJ_debugtup(outerSlot);
 509 }
 510
 511 static void
 512 ExecMergeTupleDumpInner(MergeJoinState *mergestate)
 513 {
 514         TupleTableSlot *innerSlot = mergestate->mj_InnerTupleSlot;
 515
 516         printf("==== inner tuple ====\n");
 517         if (TupIsNull(innerSlot))
 518                 printf("(nil)\n");
 519         else
 520                 MJ_debugtup(innerSlot);
 521 }
 522
 523 static void
 524 ExecMergeTupleDumpMarked(MergeJoinState *mergestate)
 525 {
 526         TupleTableSlot *markedSlot = mergestate->mj_MarkedTupleSlot;
 527
 528         printf("==== marked tuple ====\n");
 529         if (TupIsNull(markedSlot))
 530                 printf("(nil)\n");
 531         else
 532                 MJ_debugtup(markedSlot);
 533 }
 534
 535 static void
 536 ExecMergeTupleDump(MergeJoinState *mergestate)
 537 {
 538         printf("******** ExecMergeTupleDump ********\n");
 539
 540         ExecMergeTupleDumpOuter(mergestate);
 541         ExecMergeTupleDumpInner(mergestate);
 542         ExecMergeTupleDumpMarked(mergestate);
 543
 544         printf("******** \n");
 545 }
 546 #endif
 547
 548 /* ----------------------------------------------------------------
 549  *              ExecMergeJoin
 550  * ----------------------------------------------------------------
 551  */
 552 TupleTableSlot *
 553 ExecMergeJoin(MergeJoinState *node)
 554 {
 555         EState     *estate;
 556         List       *joinqual;
 557         List       *otherqual;
 558         bool            qualResult;
 559         int32           compareResult;
 560         PlanState  *innerPlan;
 561         TupleTableSlot *innerTupleSlot;
 562         PlanState  *outerPlan;
 563         TupleTableSlot *outerTupleSlot;
 564         ExprContext *econtext;
 565         bool            doFillOuter;
 566         bool            doFillInner;
 567
 568         /*
 569          * get information from node
 570          */
 571         estate = node->js.ps.state;
 572         innerPlan = innerPlanState(node);
 573         outerPlan = outerPlanState(node);
 574         econtext = node->js.ps.ps_ExprContext;
 575         joinqual = node->js.joinqual;
 576         otherqual = node->js.ps.qual;
 577         doFillOuter = node->mj_FillOuter;
 578         doFillInner = node->mj_FillInner;
 579
 580         /*
 581          * Check to see if we're still projecting out tuples from a previous join
 582          * tuple (because there is a function-returning-set in the projection
 583          * expressions).  If so, try to project another one.
 584          */
 585         if (node->js.ps.ps_TupFromTlist)
 586         {
 587                 TupleTableSlot *result;
 588                 ExprDoneCond isDone;
 589
 590                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 591                 if (isDone == ExprMultipleResult)
 592                         return result;
 593                 /* Done with that source tuple... */
 594                 node->js.ps.ps_TupFromTlist = false;
 595         }
 596
 597         /*
 598          * Reset per-tuple memory context to free any expression evaluation
 599          * storage allocated in the previous tuple cycle.  Note this can't happen
 600          * until we're done projecting out tuples from a join tuple.
 601          */
 602         ResetExprContext(econtext);
 603
 604         /*
 605          * ok, everything is setup.. let's go to work
 606          */
 607         for (;;)
 608         {
 609                 MJ_dump(node);
 610
 611                 /*
 612                  * get the current state of the join and do things accordingly.
 613                  */
 614                 switch (node->mj_JoinState)
 615                 {
 616                                 /*
 617                                  * EXEC_MJ_INITIALIZE_OUTER means that this is the first time
 618                                  * ExecMergeJoin() has been called and so we have to fetch the
 619                                  * first matchable tuple for both outer and inner subplans. We
 620                                  * do the outer side in INITIALIZE_OUTER state, then advance
 621                                  * to INITIALIZE_INNER state for the inner subplan.
 622                                  */
 623                         case EXEC_MJ_INITIALIZE_OUTER:
 624                                 MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_OUTER\n");
 625
 626                                 outerTupleSlot = ExecProcNode(outerPlan);
 627                                 node->mj_OuterTupleSlot = outerTupleSlot;
 628                                 if (TupIsNull(outerTupleSlot))
 629                                 {
 630                                         MJ_printf("ExecMergeJoin: nothing in outer subplan\n");
 631                                         if (doFillInner)
 632                                         {
 633                                                 /*
 634                                                  * Need to emit right-join tuples for remaining inner
 635                                                  * tuples.      We set MatchedInner = true to force the
 636                                                  * ENDOUTER state to advance inner.
 637                                                  */
 638                                                 node->mj_JoinState = EXEC_MJ_ENDOUTER;
 639                                                 node->mj_MatchedInner = true;
 640                                                 break;
 641                                         }
 642                                         /* Otherwise we're done. */
 643                                         return NULL;
 644                                 }
 645
 646                                 /* Compute join values and check for unmatchability */
 647                                 if (MJEvalOuterValues(node))
 648                                 {
 649                                         /* OK to go get the first inner tuple */
 650                                         node->mj_JoinState = EXEC_MJ_INITIALIZE_INNER;
 651                                 }
 652                                 else
 653                                 {
 654                                         /* Stay in same state to fetch next outer tuple */
 655                                         if (doFillOuter)
 656                                         {
 657                                                 /*
 658                                                  * Generate a fake join tuple with nulls for the inner
 659                                                  * tuple, and return it if it passes the non-join
 660                                                  * quals.
 661                                                  */
 662                                                 TupleTableSlot *result;
 663
 664                                                 result = MJFillOuter(node);
 665                                                 if (result)
 666                                                         return result;
 667                                         }
 668                                 }
 669                                 break;
 670
 671                         case EXEC_MJ_INITIALIZE_INNER:
 672                                 MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_INNER\n");
 673
 674                                 innerTupleSlot = ExecProcNode(innerPlan);
 675                                 node->mj_InnerTupleSlot = innerTupleSlot;
 676                                 if (TupIsNull(innerTupleSlot))
 677                                 {
 678                                         MJ_printf("ExecMergeJoin: nothing in inner subplan\n");
 679                                         if (doFillOuter)
 680                                         {
 681                                                 /*
 682                                                  * Need to emit left-join tuples for all outer tuples,
 683                                                  * including the one we just fetched.  We set
 684                                                  * MatchedOuter = false to force the ENDINNER state to
 685                                                  * emit first tuple before advancing outer.
 686                                                  */
 687                                                 node->mj_JoinState = EXEC_MJ_ENDINNER;
 688                                                 node->mj_MatchedOuter = false;
 689                                                 break;
 690                                         }
 691                                         /* Otherwise we're done. */
 692                                         return NULL;
 693                                 }
 694
 695                                 /* Compute join values and check for unmatchability */
 696                                 if (MJEvalInnerValues(node, innerTupleSlot))
 697                                 {
 698                                         /*
 699                                          * OK, we have the initial tuples.      Begin by skipping
 700                                          * non-matching tuples.
 701                                          */
 702                                         node->mj_JoinState = EXEC_MJ_SKIP_TEST;
 703                                 }
 704                                 else
 705                                 {
 706                                         /* Mark before advancing, if wanted */
 707                                         if (node->mj_ExtraMarks)
 708                                                 ExecMarkPos(innerPlan);
 709                                         /* Stay in same state to fetch next inner tuple */
 710                                         if (doFillInner)
 711                                         {
 712                                                 /*
 713                                                  * Generate a fake join tuple with nulls for the outer
 714                                                  * tuple, and return it if it passes the non-join
 715                                                  * quals.
 716                                                  */
 717                                                 TupleTableSlot *result;
 718
 719                                                 result = MJFillInner(node);
 720                                                 if (result)
 721                                                         return result;
 722                                         }
 723                                 }
 724                                 break;
 725
 726                                 /*
 727                                  * EXEC_MJ_JOINTUPLES means we have two tuples which satisfied
 728                                  * the merge clause so we join them and then proceed to get
 729                                  * the next inner tuple (EXEC_MJ_NEXTINNER).
 730                                  */
 731                         case EXEC_MJ_JOINTUPLES:
 732                                 MJ_printf("ExecMergeJoin: EXEC_MJ_JOINTUPLES\n");
 733
 734                                 /*
 735                                  * Set the next state machine state.  The right things will
 736                                  * happen whether we return this join tuple or just fall
 737                                  * through to continue the state machine execution.
 738                                  */
 739                                 node->mj_JoinState = EXEC_MJ_NEXTINNER;
 740
 741                                 /*
 742                                  * Check the extra qual conditions to see if we actually want
 743                                  * to return this join tuple.  If not, can proceed with merge.
 744                                  * We must distinguish the additional joinquals (which must
 745                                  * pass to consider the tuples "matched" for outer-join logic)
 746                                  * from the otherquals (which must pass before we actually
 747                                  * return the tuple).
 748                                  *
 749                                  * We don't bother with a ResetExprContext here, on the
 750                                  * assumption that we just did one while checking the merge
 751                                  * qual.  One per tuple should be sufficient.  We do have to
 752                                  * set up the econtext links to the tuples for ExecQual to
 753                                  * use.
 754                                  */
 755                                 outerTupleSlot = node->mj_OuterTupleSlot;
 756                                 econtext->ecxt_outertuple = outerTupleSlot;
 757                                 innerTupleSlot = node->mj_InnerTupleSlot;
 758                                 econtext->ecxt_innertuple = innerTupleSlot;
 759
 760                                 qualResult = (joinqual == NIL ||
 761                                                           ExecQual(joinqual, econtext, false));
 762                                 MJ_DEBUG_QUAL(joinqual, qualResult);
 763
 764                                 if (qualResult)
 765                                 {
 766                                         node->mj_MatchedOuter = true;
 767                                         node->mj_MatchedInner = true;
 768
 769                                         /* In an antijoin, we never return a matched tuple */
 770                                         if (node->js.jointype == JOIN_ANTI)
 771                                         {
 772                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 773                                                 break;
 774                                         }
 775
 776                                         /*
 777                                          * In a semijoin, we'll consider returning the first match,
 778                                          * but after that we're done with this outer tuple.
 779                                          */
 780                                         if (node->js.jointype == JOIN_SEMI)
 781                                                 node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 782
 783                                         qualResult = (otherqual == NIL ||
 784                                                                   ExecQual(otherqual, econtext, false));
 785                                         MJ_DEBUG_QUAL(otherqual, qualResult);
 786
 787                                         if (qualResult)
 788                                         {
 789                                                 /*
 790                                                  * qualification succeeded.  now form the desired
 791                                                  * projection tuple and return the slot containing it.
 792                                                  */
 793                                                 TupleTableSlot *result;
 794                                                 ExprDoneCond isDone;
 795
 796                                                 MJ_printf("ExecMergeJoin: returning tuple\n");
 797
 798                                                 result = ExecProject(node->js.ps.ps_ProjInfo,
 799                                                                                          &isDone);
 800
 801                                                 if (isDone != ExprEndResult)
 802                                                 {
 803                                                         node->js.ps.ps_TupFromTlist =
 804                                                                 (isDone == ExprMultipleResult);
 805                                                         return result;
 806                                                 }
 807                                         }
 808                                 }
 809                                 break;
 810
 811                                 /*
 812                                  * EXEC_MJ_NEXTINNER means advance the inner scan to the next
 813                                  * tuple. If the tuple is not nil, we then proceed to test it
 814                                  * against the join qualification.
 815                                  *
 816                                  * Before advancing, we check to see if we must emit an
 817                                  * outer-join fill tuple for this inner tuple.
 818                                  */
 819                         case EXEC_MJ_NEXTINNER:
 820                                 MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTINNER\n");
 821
 822                                 if (doFillInner && !node->mj_MatchedInner)
 823                                 {
 824                                         /*
 825                                          * Generate a fake join tuple with nulls for the outer
 826                                          * tuple, and return it if it passes the non-join quals.
 827                                          */
 828                                         TupleTableSlot *result;
 829
 830                                         node->mj_MatchedInner = true;           /* do it only once */
 831
 832                                         result = MJFillInner(node);
 833                                         if (result)
 834                                                 return result;
 835                                 }
 836
 837                                 /*
 838                                  * now we get the next inner tuple, if any.  If there's none,
 839                                  * advance to next outer tuple (which may be able to join to
 840                                  * previously marked tuples).
 841                                  *
 842                                  * NB: must NOT do "extraMarks" here, since we may need to
 843                                  * return to previously marked tuples.
 844                                  */
 845                                 innerTupleSlot = ExecProcNode(innerPlan);
 846                                 node->mj_InnerTupleSlot = innerTupleSlot;
 847                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
 848                                 node->mj_MatchedInner = false;
 849
 850                                 if (TupIsNull(innerTupleSlot))
 851                                 {
 852                                         node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 853                                         break;
 854                                 }
 855
 856                                 /*
 857                                  * Load up the new inner tuple's comparison values.  If we see
 858                                  * that it contains a NULL and hence can't match any outer
 859                                  * tuple, we can skip the comparison and assume the new tuple
 860                                  * is greater than current outer.
 861                                  */
 862                                 if (!MJEvalInnerValues(node, innerTupleSlot))
 863                                 {
 864                                         node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 865                                         break;
 866                                 }
 867
 868                                 /*
 869                                  * Test the new inner tuple to see if it matches outer.
 870                                  *
 871                                  * If they do match, then we join them and move on to the next
 872                                  * inner tuple (EXEC_MJ_JOINTUPLES).
 873                                  *
 874                                  * If they do not match then advance to next outer tuple.
 875                                  */
 876                                 compareResult = MJCompare(node);
 877                                 MJ_DEBUG_COMPARE(compareResult);
 878
 879                                 if (compareResult == 0)
 880                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
 881                                 else
 882                                 {
 883                                         Assert(compareResult < 0);
 884                                         node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 885                                 }
 886                                 break;
 887
 888                                 /*-------------------------------------------
 889                                  * EXEC_MJ_NEXTOUTER means
 890                                  *
 891                                  *                              outer inner
 892                                  * outer tuple -  5             5  - marked tuple
 893                                  *                                5             5
 894                                  *                                6             6  - inner tuple
 895                                  *                                7             7
 896                                  *
 897                                  * we know we just bumped into the
 898                                  * first inner tuple > current outer tuple (or possibly
 899                                  * the end of the inner stream)
 900                                  * so get a new outer tuple and then
 901                                  * proceed to test it against the marked tuple
 902                                  * (EXEC_MJ_TESTOUTER)
 903                                  *
 904                                  * Before advancing, we check to see if we must emit an
 905                                  * outer-join fill tuple for this outer tuple.
 906                                  *------------------------------------------------
 907                                  */
 908                         case EXEC_MJ_NEXTOUTER:
 909                                 MJ_printf("ExecMergeJoin: EXEC_MJ_NEXTOUTER\n");
 910
 911                                 if (doFillOuter && !node->mj_MatchedOuter)
 912                                 {
 913                                         /*
 914                                          * Generate a fake join tuple with nulls for the inner
 915                                          * tuple, and return it if it passes the non-join quals.
 916                                          */
 917                                         TupleTableSlot *result;
 918
 919                                         node->mj_MatchedOuter = true;           /* do it only once */
 920
 921                                         result = MJFillOuter(node);
 922                                         if (result)
 923                                                 return result;
 924                                 }
 925
 926                                 /*
 927                                  * now we get the next outer tuple, if any
 928                                  */
 929                                 outerTupleSlot = ExecProcNode(outerPlan);
 930                                 node->mj_OuterTupleSlot = outerTupleSlot;
 931                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
 932                                 node->mj_MatchedOuter = false;
 933
 934                                 /*
 935                                  * if the outer tuple is null then we are done with the join,
 936                                  * unless we have inner tuples we need to null-fill.
 937                                  */
 938                                 if (TupIsNull(outerTupleSlot))
 939                                 {
 940                                         MJ_printf("ExecMergeJoin: end of outer subplan\n");
 941                                         innerTupleSlot = node->mj_InnerTupleSlot;
 942                                         if (doFillInner && !TupIsNull(innerTupleSlot))
 943                                         {
 944                                                 /*
 945                                                  * Need to emit right-join tuples for remaining inner
 946                                                  * tuples.
 947                                                  */
 948                                                 node->mj_JoinState = EXEC_MJ_ENDOUTER;
 949                                                 break;
 950                                         }
 951                                         /* Otherwise we're done. */
 952                                         return NULL;
 953                                 }
 954
 955                                 /* Compute join values and check for unmatchability */
 956                                 if (MJEvalOuterValues(node))
 957                                 {
 958                                         /* Go test the new tuple against the marked tuple */
 959                                         node->mj_JoinState = EXEC_MJ_TESTOUTER;
 960                                 }
 961                                 else
 962                                 {
 963                                         /* Can't match, so fetch next outer tuple */
 964                                         node->mj_JoinState = EXEC_MJ_NEXTOUTER;
 965                                 }
 966                                 break;
 967
 968                                 /*--------------------------------------------------------
 969                                  * EXEC_MJ_TESTOUTER If the new outer tuple and the marked
 970                                  * tuple satisfy the merge clause then we know we have
 971                                  * duplicates in the outer scan so we have to restore the
 972                                  * inner scan to the marked tuple and proceed to join the
 973                                  * new outer tuple with the inner tuples.
 974                                  *
 975                                  * This is the case when
 976                                  *                                                outer inner
 977                                  *                                                      4         5  - marked tuple
 978                                  *                       outer tuple -  5         5
 979                                  *               new outer tuple -      5         5
 980                                  *                                                      6         8  - inner tuple
 981                                  *                                                      7        12
 982                                  *
 983                                  *                              new outer tuple == marked tuple
 984                                  *
 985                                  * If the outer tuple fails the test, then we are done
 986                                  * with the marked tuples, and we have to look for a
 987                                  * match to the current inner tuple.  So we will
 988                                  * proceed to skip outer tuples until outer >= inner
 989                                  * (EXEC_MJ_SKIP_TEST).
 990                                  *
 991                                  *              This is the case when
 992                                  *
 993                                  *                                                outer inner
 994                                  *                                                      5         5  - marked tuple
 995                                  *                       outer tuple -  5         5
 996                                  *               new outer tuple -      6         8  - inner tuple
 997                                  *                                                      7        12
 998                                  *
 999                                  *                              new outer tuple > marked tuple
1000                                  *
1001                                  *---------------------------------------------------------
1002                                  */
1003                         case EXEC_MJ_TESTOUTER:
1004                                 MJ_printf("ExecMergeJoin: EXEC_MJ_TESTOUTER\n");
1005
1006                                 /*
1007                                  * Here we must compare the outer tuple with the marked inner
1008                                  * tuple.  (We can ignore the result of MJEvalInnerValues,
1009                                  * since the marked inner tuple is certainly matchable.)
1010                                  */
1011                                 innerTupleSlot = node->mj_MarkedTupleSlot;
1012                                 (void) MJEvalInnerValues(node, innerTupleSlot);
1013
1014                                 compareResult = MJCompare(node);
1015                                 MJ_DEBUG_COMPARE(compareResult);
1016
1017                                 if (compareResult == 0)
1018                                 {
1019                                         /*
1020                                          * the merge clause matched so now we restore the inner
1021                                          * scan position to the first mark, and go join that tuple
1022                                          * (and any following ones) to the new outer.
1023                                          *
1024                                          * NOTE: we do not need to worry about the MatchedInner
1025                                          * state for the rescanned inner tuples.  We know all of
1026                                          * them will match this new outer tuple and therefore
1027                                          * won't be emitted as fill tuples.  This works *only*
1028                                          * because we require the extra joinquals to be nil when
1029                                          * doing a right or full join --- otherwise some of the
1030                                          * rescanned tuples might fail the extra joinquals.
1031                                          */
1032                                         ExecRestrPos(innerPlan);
1033
1034                                         /*
1035                                          * ExecRestrPos probably should give us back a new Slot,
1036                                          * but since it doesn't, use the marked slot.  (The
1037                                          * previously returned mj_InnerTupleSlot cannot be assumed
1038                                          * to hold the required tuple.)
1039                                          */
1040                                         node->mj_InnerTupleSlot = innerTupleSlot;
1041                                         /* we need not do MJEvalInnerValues again */
1042
1043                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
1044                                 }
1045                                 else
1046                                 {
1047                                         /* ----------------
1048                                          *      if the new outer tuple didn't match the marked inner
1049                                          *      tuple then we have a case like:
1050                                          *
1051                                          *                       outer inner
1052                                          *                         4     4      - marked tuple
1053                                          * new outer - 5         4
1054                                          *                         6     5      - inner tuple
1055                                          *                         7
1056                                          *
1057                                          *      which means that all subsequent outer tuples will be
1058                                          *      larger than our marked inner tuples.  So we need not
1059                                          *      revisit any of the marked tuples but can proceed to
1060                                          *      look for a match to the current inner.  If there's
1061                                          *      no more inners, we are done.
1062                                          * ----------------
1063                                          */
1064                                         Assert(compareResult > 0);
1065                                         innerTupleSlot = node->mj_InnerTupleSlot;
1066                                         if (TupIsNull(innerTupleSlot))
1067                                         {
1068                                                 if (doFillOuter)
1069                                                 {
1070                                                         /*
1071                                                          * Need to emit left-join tuples for remaining
1072                                                          * outer tuples.
1073                                                          */
1074                                                         node->mj_JoinState = EXEC_MJ_ENDINNER;
1075                                                         break;
1076                                                 }
1077                                                 /* Otherwise we're done. */
1078                                                 return NULL;
1079                                         }
1080
1081                                         /* reload comparison data for current inner */
1082                                         if (MJEvalInnerValues(node, innerTupleSlot))
1083                                         {
1084                                                 /* proceed to compare it to the current outer */
1085                                                 node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1086                                         }
1087                                         else
1088                                         {
1089                                                 /*
1090                                                  * current inner can't possibly match any outer;
1091                                                  * better to advance the inner scan than the outer.
1092                                                  */
1093                                                 node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1094                                         }
1095                                 }
1096                                 break;
1097
1098                                 /*----------------------------------------------------------
1099                                  * EXEC_MJ_SKIP means compare tuples and if they do not
1100                                  * match, skip whichever is lesser.
1101                                  *
1102                                  * For example:
1103                                  *
1104                                  *                              outer inner
1105                                  *                                5             5
1106                                  *                                5             5
1107                                  * outer tuple -  6             8  - inner tuple
1108                                  *                                7    12
1109                                  *                                8    14
1110                                  *
1111                                  * we have to advance the outer scan
1112                                  * until we find the outer 8.
1113                                  *
1114                                  * On the other hand:
1115                                  *
1116                                  *                              outer inner
1117                                  *                                5             5
1118                                  *                                5             5
1119                                  * outer tuple - 12             8  - inner tuple
1120                                  *                               14    10
1121                                  *                               17    12
1122                                  *
1123                                  * we have to advance the inner scan
1124                                  * until we find the inner 12.
1125                                  *----------------------------------------------------------
1126                                  */
1127                         case EXEC_MJ_SKIP_TEST:
1128                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIP_TEST\n");
1129
1130                                 /*
1131                                  * before we advance, make sure the current tuples do not
1132                                  * satisfy the mergeclauses.  If they do, then we update the
1133                                  * marked tuple position and go join them.
1134                                  */
1135                                 compareResult = MJCompare(node);
1136                                 MJ_DEBUG_COMPARE(compareResult);
1137
1138                                 if (compareResult == 0)
1139                                 {
1140                                         ExecMarkPos(innerPlan);
1141
1142                                         MarkInnerTuple(node->mj_InnerTupleSlot, node);
1143
1144                                         node->mj_JoinState = EXEC_MJ_JOINTUPLES;
1145                                 }
1146                                 else if (compareResult < 0)
1147                                         node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE;
1148                                 else
1149                                         /* compareResult > 0 */
1150                                         node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1151                                 break;
1152
1153                                 /*
1154                                  * SKIPOUTER_ADVANCE: advance over an outer tuple that is
1155                                  * known not to join to any inner tuple.
1156                                  *
1157                                  * Before advancing, we check to see if we must emit an
1158                                  * outer-join fill tuple for this outer tuple.
1159                                  */
1160                         case EXEC_MJ_SKIPOUTER_ADVANCE:
1161                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPOUTER_ADVANCE\n");
1162
1163                                 if (doFillOuter && !node->mj_MatchedOuter)
1164                                 {
1165                                         /*
1166                                          * Generate a fake join tuple with nulls for the inner
1167                                          * tuple, and return it if it passes the non-join quals.
1168                                          */
1169                                         TupleTableSlot *result;
1170
1171                                         node->mj_MatchedOuter = true;           /* do it only once */
1172
1173                                         result = MJFillOuter(node);
1174                                         if (result)
1175                                                 return result;
1176                                 }
1177
1178                                 /*
1179                                  * now we get the next outer tuple, if any
1180                                  */
1181                                 outerTupleSlot = ExecProcNode(outerPlan);
1182                                 node->mj_OuterTupleSlot = outerTupleSlot;
1183                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
1184                                 node->mj_MatchedOuter = false;
1185
1186                                 /*
1187                                  * if the outer tuple is null then we are done with the join,
1188                                  * unless we have inner tuples we need to null-fill.
1189                                  */
1190                                 if (TupIsNull(outerTupleSlot))
1191                                 {
1192                                         MJ_printf("ExecMergeJoin: end of outer subplan\n");
1193                                         innerTupleSlot = node->mj_InnerTupleSlot;
1194                                         if (doFillInner && !TupIsNull(innerTupleSlot))
1195                                         {
1196                                                 /*
1197                                                  * Need to emit right-join tuples for remaining inner
1198                                                  * tuples.
1199                                                  */
1200                                                 node->mj_JoinState = EXEC_MJ_ENDOUTER;
1201                                                 break;
1202                                         }
1203                                         /* Otherwise we're done. */
1204                                         return NULL;
1205                                 }
1206
1207                                 /* Compute join values and check for unmatchability */
1208                                 if (MJEvalOuterValues(node))
1209                                 {
1210                                         /* Go test the new tuple against the current inner */
1211                                         node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1212                                 }
1213                                 else
1214                                 {
1215                                         /* Can't match, so fetch next outer tuple */
1216                                         node->mj_JoinState = EXEC_MJ_SKIPOUTER_ADVANCE;
1217                                 }
1218                                 break;
1219
1220                                 /*
1221                                  * SKIPINNER_ADVANCE: advance over an inner tuple that is
1222                                  * known not to join to any outer tuple.
1223                                  *
1224                                  * Before advancing, we check to see if we must emit an
1225                                  * outer-join fill tuple for this inner tuple.
1226                                  */
1227                         case EXEC_MJ_SKIPINNER_ADVANCE:
1228                                 MJ_printf("ExecMergeJoin: EXEC_MJ_SKIPINNER_ADVANCE\n");
1229
1230                                 if (doFillInner && !node->mj_MatchedInner)
1231                                 {
1232                                         /*
1233                                          * Generate a fake join tuple with nulls for the outer
1234                                          * tuple, and return it if it passes the non-join quals.
1235                                          */
1236                                         TupleTableSlot *result;
1237
1238                                         node->mj_MatchedInner = true;           /* do it only once */
1239
1240                                         result = MJFillInner(node);
1241                                         if (result)
1242                                                 return result;
1243                                 }
1244
1245                                 /* Mark before advancing, if wanted */
1246                                 if (node->mj_ExtraMarks)
1247                                         ExecMarkPos(innerPlan);
1248
1249                                 /*
1250                                  * now we get the next inner tuple, if any
1251                                  */
1252                                 innerTupleSlot = ExecProcNode(innerPlan);
1253                                 node->mj_InnerTupleSlot = innerTupleSlot;
1254                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
1255                                 node->mj_MatchedInner = false;
1256
1257                                 /*
1258                                  * if the inner tuple is null then we are done with the join,
1259                                  * unless we have outer tuples we need to null-fill.
1260                                  */
1261                                 if (TupIsNull(innerTupleSlot))
1262                                 {
1263                                         MJ_printf("ExecMergeJoin: end of inner subplan\n");
1264                                         outerTupleSlot = node->mj_OuterTupleSlot;
1265                                         if (doFillOuter && !TupIsNull(outerTupleSlot))
1266                                         {
1267                                                 /*
1268                                                  * Need to emit left-join tuples for remaining outer
1269                                                  * tuples.
1270                                                  */
1271                                                 node->mj_JoinState = EXEC_MJ_ENDINNER;
1272                                                 break;
1273                                         }
1274                                         /* Otherwise we're done. */
1275                                         return NULL;
1276                                 }
1277
1278                                 /* Compute join values and check for unmatchability */
1279                                 if (MJEvalInnerValues(node, innerTupleSlot))
1280                                 {
1281                                         /* proceed to compare it to the current outer */
1282                                         node->mj_JoinState = EXEC_MJ_SKIP_TEST;
1283                                 }
1284                                 else
1285                                 {
1286                                         /*
1287                                          * current inner can't possibly match any outer; better to
1288                                          * advance the inner scan than the outer.
1289                                          */
1290                                         node->mj_JoinState = EXEC_MJ_SKIPINNER_ADVANCE;
1291                                 }
1292                                 break;
1293
1294                                 /*
1295                                  * EXEC_MJ_ENDOUTER means we have run out of outer tuples, but
1296                                  * are doing a right/full join and therefore must null-fill
1297                                  * any remaing unmatched inner tuples.
1298                                  */
1299                         case EXEC_MJ_ENDOUTER:
1300                                 MJ_printf("ExecMergeJoin: EXEC_MJ_ENDOUTER\n");
1301
1302                                 Assert(doFillInner);
1303
1304                                 if (!node->mj_MatchedInner)
1305                                 {
1306                                         /*
1307                                          * Generate a fake join tuple with nulls for the outer
1308                                          * tuple, and return it if it passes the non-join quals.
1309                                          */
1310                                         TupleTableSlot *result;
1311
1312                                         node->mj_MatchedInner = true;           /* do it only once */
1313
1314                                         result = MJFillInner(node);
1315                                         if (result)
1316                                                 return result;
1317                                 }
1318
1319                                 /* Mark before advancing, if wanted */
1320                                 if (node->mj_ExtraMarks)
1321                                         ExecMarkPos(innerPlan);
1322
1323                                 /*
1324                                  * now we get the next inner tuple, if any
1325                                  */
1326                                 innerTupleSlot = ExecProcNode(innerPlan);
1327                                 node->mj_InnerTupleSlot = innerTupleSlot;
1328                                 MJ_DEBUG_PROC_NODE(innerTupleSlot);
1329                                 node->mj_MatchedInner = false;
1330
1331                                 if (TupIsNull(innerTupleSlot))
1332                                 {
1333                                         MJ_printf("ExecMergeJoin: end of inner subplan\n");
1334                                         return NULL;
1335                                 }
1336
1337                                 /* Else remain in ENDOUTER state and process next tuple. */
1338                                 break;
1339
1340                                 /*
1341                                  * EXEC_MJ_ENDINNER means we have run out of inner tuples, but
1342                                  * are doing a left/full join and therefore must null- fill
1343                                  * any remaing unmatched outer tuples.
1344                                  */
1345                         case EXEC_MJ_ENDINNER:
1346                                 MJ_printf("ExecMergeJoin: EXEC_MJ_ENDINNER\n");
1347
1348                                 Assert(doFillOuter);
1349
1350                                 if (!node->mj_MatchedOuter)
1351                                 {
1352                                         /*
1353                                          * Generate a fake join tuple with nulls for the inner
1354                                          * tuple, and return it if it passes the non-join quals.
1355                                          */
1356                                         TupleTableSlot *result;
1357
1358                                         node->mj_MatchedOuter = true;           /* do it only once */
1359
1360                                         result = MJFillOuter(node);
1361                                         if (result)
1362                                                 return result;
1363                                 }
1364
1365                                 /*
1366                                  * now we get the next outer tuple, if any
1367                                  */
1368                                 outerTupleSlot = ExecProcNode(outerPlan);
1369                                 node->mj_OuterTupleSlot = outerTupleSlot;
1370                                 MJ_DEBUG_PROC_NODE(outerTupleSlot);
1371                                 node->mj_MatchedOuter = false;
1372
1373                                 if (TupIsNull(outerTupleSlot))
1374                                 {
1375                                         MJ_printf("ExecMergeJoin: end of outer subplan\n");
1376                                         return NULL;
1377                                 }
1378
1379                                 /* Else remain in ENDINNER state and process next tuple. */
1380                                 break;
1381
1382                                 /*
1383                                  * broken state value?
1384                                  */
1385                         default:
1386                                 elog(ERROR, "unrecognized mergejoin state: %d",
1387                                          (int) node->mj_JoinState);
1388                 }
1389         }
1390 }
1391
1392 /* ----------------------------------------------------------------
1393  *              ExecInitMergeJoin
1394  * ----------------------------------------------------------------
1395  */
1396 MergeJoinState *
1397 ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
1398 {
1399         MergeJoinState *mergestate;
1400
1401         /* check for unsupported flags */
1402         Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
1403
1404         MJ1_printf("ExecInitMergeJoin: %s\n",
1405                            "initializing node");
1406
1407         /*
1408          * create state structure
1409          */
1410         mergestate = makeNode(MergeJoinState);
1411         mergestate->js.ps.plan = (Plan *) node;
1412         mergestate->js.ps.state = estate;
1413
1414         /*
1415          * Miscellaneous initialization
1416          *
1417          * create expression context for node
1418          */
1419         ExecAssignExprContext(estate, &mergestate->js.ps);
1420
1421         /*
1422          * we need two additional econtexts in which we can compute the join
1423          * expressions from the left and right input tuples.  The node's regular
1424          * econtext won't do because it gets reset too often.
1425          */
1426         mergestate->mj_OuterEContext = CreateExprContext(estate);
1427         mergestate->mj_InnerEContext = CreateExprContext(estate);
1428
1429         /*
1430          * initialize child expressions
1431          */
1432         mergestate->js.ps.targetlist = (List *)
1433                 ExecInitExpr((Expr *) node->join.plan.targetlist,
1434                                          (PlanState *) mergestate);
1435         mergestate->js.ps.qual = (List *)
1436                 ExecInitExpr((Expr *) node->join.plan.qual,
1437                                          (PlanState *) mergestate);
1438         mergestate->js.jointype = node->join.jointype;
1439         mergestate->js.joinqual = (List *)
1440                 ExecInitExpr((Expr *) node->join.joinqual,
1441                                          (PlanState *) mergestate);
1442         /* mergeclauses are handled below */
1443
1444         /*
1445          * initialize child nodes
1446          *
1447          * inner child must support MARK/RESTORE.
1448          */
1449         outerPlanState(mergestate) = ExecInitNode(outerPlan(node), estate, eflags);
1450         innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate,
1451                                                                                           eflags | EXEC_FLAG_MARK);
1452
1453         /*
1454          * For certain types of inner child nodes, it is advantageous to issue
1455          * MARK every time we advance past an inner tuple we will never return to.
1456          * For other types, MARK on a tuple we cannot return to is a waste of
1457          * cycles.      Detect which case applies and set mj_ExtraMarks if we want to
1458          * issue "unnecessary" MARK calls.
1459          *
1460          * Currently, only Material wants the extra MARKs, and it will be helpful
1461          * only if eflags doesn't specify REWIND.
1462          */
1463         if (IsA(innerPlan(node), Material) &&
1464                 (eflags & EXEC_FLAG_REWIND) == 0)
1465                 mergestate->mj_ExtraMarks = true;
1466         else
1467                 mergestate->mj_ExtraMarks = false;
1468
1469 #define MERGEJOIN_NSLOTS 4
1470
1471         /*
1472          * tuple table initialization
1473          */
1474         ExecInitResultTupleSlot(estate, &mergestate->js.ps);
1475
1476         mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate);
1477         ExecSetSlotDescriptor(mergestate->mj_MarkedTupleSlot,
1478                                                   ExecGetResultType(innerPlanState(mergestate)));
1479
1480         switch (node->join.jointype)
1481         {
1482                 case JOIN_INNER:
1483                 case JOIN_SEMI:
1484                         mergestate->mj_FillOuter = false;
1485                         mergestate->mj_FillInner = false;
1486                         break;
1487                 case JOIN_LEFT:
1488                 case JOIN_ANTI:
1489                         mergestate->mj_FillOuter = true;
1490                         mergestate->mj_FillInner = false;
1491                         mergestate->mj_NullInnerTupleSlot =
1492                                 ExecInitNullTupleSlot(estate,
1493                                                           ExecGetResultType(innerPlanState(mergestate)));
1494                         break;
1495                 case JOIN_RIGHT:
1496                         mergestate->mj_FillOuter = false;
1497                         mergestate->mj_FillInner = true;
1498                         mergestate->mj_NullOuterTupleSlot =
1499                                 ExecInitNullTupleSlot(estate,
1500                                                           ExecGetResultType(outerPlanState(mergestate)));
1501
1502                         /*
1503                          * Can't handle right or full join with non-nil extra joinclauses.
1504                          * This should have been caught by planner.
1505                          */
1506                         if (node->join.joinqual != NIL)
1507                                 ereport(ERROR,
1508                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1509                                                  errmsg("RIGHT JOIN is only supported with merge-joinable join conditions")));
1510                         break;
1511                 case JOIN_FULL:
1512                         mergestate->mj_FillOuter = true;
1513                         mergestate->mj_FillInner = true;
1514                         mergestate->mj_NullOuterTupleSlot =
1515                                 ExecInitNullTupleSlot(estate,
1516                                                           ExecGetResultType(outerPlanState(mergestate)));
1517                         mergestate->mj_NullInnerTupleSlot =
1518                                 ExecInitNullTupleSlot(estate,
1519                                                           ExecGetResultType(innerPlanState(mergestate)));
1520
1521                         /*
1522                          * Can't handle right or full join with non-nil extra joinclauses.
1523                          */
1524                         if (node->join.joinqual != NIL)
1525                                 ereport(ERROR,
1526                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1527                                                  errmsg("FULL JOIN is only supported with merge-joinable join conditions")));
1528                         break;
1529                 default:
1530                         elog(ERROR, "unrecognized join type: %d",
1531                                  (int) node->join.jointype);
1532         }
1533
1534         /*
1535          * initialize tuple type and projection info
1536          */
1537         ExecAssignResultTypeFromTL(&mergestate->js.ps);
1538         ExecAssignProjectionInfo(&mergestate->js.ps, NULL);
1539
1540         /*
1541          * preprocess the merge clauses
1542          */
1543         mergestate->mj_NumClauses = list_length(node->mergeclauses);
1544         mergestate->mj_Clauses = MJExamineQuals(node->mergeclauses,
1545                                                                                         node->mergeFamilies,
1546                                                                                         node->mergeStrategies,
1547                                                                                         node->mergeNullsFirst,
1548                                                                                         (PlanState *) mergestate);
1549
1550         /*
1551          * initialize join state
1552          */
1553         mergestate->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER;
1554         mergestate->js.ps.ps_TupFromTlist = false;
1555         mergestate->mj_MatchedOuter = false;
1556         mergestate->mj_MatchedInner = false;
1557         mergestate->mj_OuterTupleSlot = NULL;
1558         mergestate->mj_InnerTupleSlot = NULL;
1559
1560         /*
1561          * initialization successful
1562          */
1563         MJ1_printf("ExecInitMergeJoin: %s\n",
1564                            "node initialized");
1565
1566         return mergestate;
1567 }
1568
1569 int
1570 ExecCountSlotsMergeJoin(MergeJoin *node)
1571 {
1572         return ExecCountSlotsNode(outerPlan((Plan *) node)) +
1573                 ExecCountSlotsNode(innerPlan((Plan *) node)) +
1574                 MERGEJOIN_NSLOTS;
1575 }
1576
1577 /* ----------------------------------------------------------------
1578  *              ExecEndMergeJoin
1579  *
1580  * old comments
1581  *              frees storage allocated through C routines.
1582  * ----------------------------------------------------------------
1583  */
1584 void
1585 ExecEndMergeJoin(MergeJoinState *node)
1586 {
1587         MJ1_printf("ExecEndMergeJoin: %s\n",
1588                            "ending node processing");
1589
1590         /*
1591          * Free the exprcontext
1592          */
1593         ExecFreeExprContext(&node->js.ps);
1594
1595         /*
1596          * clean out the tuple table
1597          */
1598         ExecClearTuple(node->js.ps.ps_ResultTupleSlot);
1599         ExecClearTuple(node->mj_MarkedTupleSlot);
1600
1601         /*
1602          * shut down the subplans
1603          */
1604         ExecEndNode(innerPlanState(node));
1605         ExecEndNode(outerPlanState(node));
1606
1607         MJ1_printf("ExecEndMergeJoin: %s\n",
1608                            "node processing ended");
1609 }
1610
1611 void
1612 ExecReScanMergeJoin(MergeJoinState *node, ExprContext *exprCtxt)
1613 {
1614         ExecClearTuple(node->mj_MarkedTupleSlot);
1615
1616         node->mj_JoinState = EXEC_MJ_INITIALIZE_OUTER;
1617         node->js.ps.ps_TupFromTlist = false;
1618         node->mj_MatchedOuter = false;
1619         node->mj_MatchedInner = false;
1620         node->mj_OuterTupleSlot = NULL;
1621         node->mj_InnerTupleSlot = NULL;
1622
1623         /*
1624          * if chgParam of subnodes is not null then plans will be re-scanned by
1625          * first ExecProcNode.
1626          */
1627         if (((PlanState *) node)->lefttree->chgParam == NULL)
1628                 ExecReScan(((PlanState *) node)->lefttree, exprCtxt);
1629         if (((PlanState *) node)->righttree->chgParam == NULL)
1630                 ExecReScan(((PlanState *) node)->righttree, exprCtxt);
1631
1632 }