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

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeNestloop.c
   4  *        routines to support nest-loop 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/nodeNestloop.c,v 1.46 2008/01/01 19:45:49 momjian Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /*
  16  *       INTERFACE ROUTINES
  17  *              ExecNestLoop     - process a nestloop join of two plans
  18  *              ExecInitNestLoop - initialize the join
  19  *              ExecEndNestLoop  - shut down the join
  20  */
  21
  22 #include "postgres.h"
  23
  24 #include "executor/execdebug.h"
  25 #include "executor/nodeNestloop.h"
  26 #include "utils/memutils.h"
  27
  28
  29 /* ----------------------------------------------------------------
  30  *              ExecNestLoop(node)
  31  *
  32  * old comments
  33  *              Returns the tuple joined from inner and outer tuples which
  34  *              satisfies the qualification clause.
  35  *
  36  *              It scans the inner relation to join with current outer tuple.
  37  *
  38  *              If none is found, next tuple from the outer relation is retrieved
  39  *              and the inner relation is scanned from the beginning again to join
  40  *              with the outer tuple.
  41  *
  42  *              NULL is returned if all the remaining outer tuples are tried and
  43  *              all fail to join with the inner tuples.
  44  *
  45  *              NULL is also returned if there is no tuple from inner relation.
  46  *
  47  *              Conditions:
  48  *                -- outerTuple contains current tuple from outer relation and
  49  *                       the right son(inner relation) maintains "cursor" at the tuple
  50  *                       returned previously.
  51  *                              This is achieved by maintaining a scan position on the outer
  52  *                              relation.
  53  *
  54  *              Initial States:
  55  *                -- the outer child and the inner child
  56  *                         are prepared to return the first tuple.
  57  * ----------------------------------------------------------------
  58  */
  59 TupleTableSlot *
  60 ExecNestLoop(NestLoopState *node)
  61 {
  62         PlanState  *innerPlan;
  63         PlanState  *outerPlan;
  64         TupleTableSlot *outerTupleSlot;
  65         TupleTableSlot *innerTupleSlot;
  66         List       *joinqual;
  67         List       *otherqual;
  68         ExprContext *econtext;
  69
  70         /*
  71          * get information from the node
  72          */
  73         ENL1_printf("getting info from node");
  74
  75         joinqual = node->js.joinqual;
  76         otherqual = node->js.ps.qual;
  77         outerPlan = outerPlanState(node);
  78         innerPlan = innerPlanState(node);
  79         econtext = node->js.ps.ps_ExprContext;
  80
  81         /*
  82          * get the current outer tuple
  83          */
  84         outerTupleSlot = node->js.ps.ps_OuterTupleSlot;
  85         econtext->ecxt_outertuple = outerTupleSlot;
  86
  87         /*
  88          * Check to see if we're still projecting out tuples from a previous join
  89          * tuple (because there is a function-returning-set in the projection
  90          * expressions).  If so, try to project another one.
  91          */
  92         if (node->js.ps.ps_TupFromTlist)
  93         {
  94                 TupleTableSlot *result;
  95                 ExprDoneCond isDone;
  96
  97                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
  98                 if (isDone == ExprMultipleResult)
  99                         return result;
 100                 /* Done with that source tuple... */
 101                 node->js.ps.ps_TupFromTlist = false;
 102         }
 103
 104         /*
 105          * If we're doing an IN join, we want to return at most one row per outer
 106          * tuple; so we can stop scanning the inner scan if we matched on the
 107          * previous try.
 108          */
 109         if (node->js.jointype == JOIN_IN &&
 110                 node->nl_MatchedOuter)
 111                 node->nl_NeedNewOuter = true;
 112
 113         /*
 114          * Reset per-tuple memory context to free any expression evaluation
 115          * storage allocated in the previous tuple cycle.  Note this can't happen
 116          * until we're done projecting out tuples from a join tuple.
 117          */
 118         ResetExprContext(econtext);
 119
 120         /*
 121          * Ok, everything is setup for the join so now loop until we return a
 122          * qualifying join tuple.
 123          */
 124         ENL1_printf("entering main loop");
 125
 126         for (;;)
 127         {
 128                 /*
 129                  * If we don't have an outer tuple, get the next one and reset the
 130                  * inner scan.
 131                  */
 132                 if (node->nl_NeedNewOuter)
 133                 {
 134                         ENL1_printf("getting new outer tuple");
 135                         outerTupleSlot = ExecProcNode(outerPlan);
 136
 137                         /*
 138                          * if there are no more outer tuples, then the join is complete..
 139                          */
 140                         if (TupIsNull(outerTupleSlot))
 141                         {
 142                                 ENL1_printf("no outer tuple, ending join");
 143                                 return NULL;
 144                         }
 145
 146                         ENL1_printf("saving new outer tuple information");
 147                         node->js.ps.ps_OuterTupleSlot = outerTupleSlot;
 148                         econtext->ecxt_outertuple = outerTupleSlot;
 149                         node->nl_NeedNewOuter = false;
 150                         node->nl_MatchedOuter = false;
 151
 152                         /*
 153                          * now rescan the inner plan
 154                          */
 155                         ENL1_printf("rescanning inner plan");
 156
 157                         /*
 158                          * The scan key of the inner plan might depend on the current
 159                          * outer tuple (e.g. in index scans), that's why we pass our expr
 160                          * context.
 161                          */
 162                         ExecReScan(innerPlan, econtext);
 163                 }
 164
 165                 /*
 166                  * we have an outerTuple, try to get the next inner tuple.
 167                  */
 168                 ENL1_printf("getting new inner tuple");
 169
 170                 innerTupleSlot = ExecProcNode(innerPlan);
 171                 econtext->ecxt_innertuple = innerTupleSlot;
 172
 173                 if (TupIsNull(innerTupleSlot))
 174                 {
 175                         ENL1_printf("no inner tuple, need new outer tuple");
 176
 177                         node->nl_NeedNewOuter = true;
 178
 179                         if (!node->nl_MatchedOuter &&
 180                                 node->js.jointype == JOIN_LEFT)
 181                         {
 182                                 /*
 183                                  * We are doing an outer join and there were no join matches
 184                                  * for this outer tuple.  Generate a fake join tuple with
 185                                  * nulls for the inner tuple, and return it if it passes the
 186                                  * non-join quals.
 187                                  */
 188                                 econtext->ecxt_innertuple = node->nl_NullInnerTupleSlot;
 189
 190                                 ENL1_printf("testing qualification for outer-join tuple");
 191
 192                                 if (ExecQual(otherqual, econtext, false))
 193                                 {
 194                                         /*
 195                                          * qualification was satisfied so we project and return
 196                                          * the slot containing the result tuple using
 197                                          * ExecProject().
 198                                          */
 199                                         TupleTableSlot *result;
 200                                         ExprDoneCond isDone;
 201
 202                                         ENL1_printf("qualification succeeded, projecting tuple");
 203
 204                                         result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 205
 206                                         if (isDone != ExprEndResult)
 207                                         {
 208                                                 node->js.ps.ps_TupFromTlist =
 209                                                         (isDone == ExprMultipleResult);
 210                                                 return result;
 211                                         }
 212                                 }
 213                         }
 214
 215                         /*
 216                          * Otherwise just return to top of loop for a new outer tuple.
 217                          */
 218                         continue;
 219                 }
 220
 221                 /*
 222                  * at this point we have a new pair of inner and outer tuples so we
 223                  * test the inner and outer tuples to see if they satisfy the node's
 224                  * qualification.
 225                  *
 226                  * Only the joinquals determine MatchedOuter status, but all quals
 227                  * must pass to actually return the tuple.
 228                  */
 229                 ENL1_printf("testing qualification");
 230
 231                 if (ExecQual(joinqual, econtext, false))
 232                 {
 233                         node->nl_MatchedOuter = true;
 234
 235                         if (otherqual == NIL || ExecQual(otherqual, econtext, false))
 236                         {
 237                                 /*
 238                                  * qualification was satisfied so we project and return the
 239                                  * slot containing the result tuple using ExecProject().
 240                                  */
 241                                 TupleTableSlot *result;
 242                                 ExprDoneCond isDone;
 243
 244                                 ENL1_printf("qualification succeeded, projecting tuple");
 245
 246                                 result = ExecProject(node->js.ps.ps_ProjInfo, &isDone);
 247
 248                                 if (isDone != ExprEndResult)
 249                                 {
 250                                         node->js.ps.ps_TupFromTlist =
 251                                                 (isDone == ExprMultipleResult);
 252                                         return result;
 253                                 }
 254                         }
 255
 256                         /* If we didn't return a tuple, may need to set NeedNewOuter */
 257                         if (node->js.jointype == JOIN_IN)
 258                                 node->nl_NeedNewOuter = true;
 259                 }
 260
 261                 /*
 262                  * Tuple fails qual, so free per-tuple memory and try again.
 263                  */
 264                 ResetExprContext(econtext);
 265
 266                 ENL1_printf("qualification failed, looping");
 267         }
 268 }
 269
 270 /* ----------------------------------------------------------------
 271  *              ExecInitNestLoop
 272  * ----------------------------------------------------------------
 273  */
 274 NestLoopState *
 275 ExecInitNestLoop(NestLoop *node, EState *estate, int eflags)
 276 {
 277         NestLoopState *nlstate;
 278
 279         /* check for unsupported flags */
 280         Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
 281
 282         NL1_printf("ExecInitNestLoop: %s\n",
 283                            "initializing node");
 284
 285         /*
 286          * create state structure
 287          */
 288         nlstate = makeNode(NestLoopState);
 289         nlstate->js.ps.plan = (Plan *) node;
 290         nlstate->js.ps.state = estate;
 291
 292         /*
 293          * Miscellaneous initialization
 294          *
 295          * create expression context for node
 296          */
 297         ExecAssignExprContext(estate, &nlstate->js.ps);
 298
 299         /*
 300          * initialize child expressions
 301          */
 302         nlstate->js.ps.targetlist = (List *)
 303                 ExecInitExpr((Expr *) node->join.plan.targetlist,
 304                                          (PlanState *) nlstate);
 305         nlstate->js.ps.qual = (List *)
 306                 ExecInitExpr((Expr *) node->join.plan.qual,
 307                                          (PlanState *) nlstate);
 308         nlstate->js.jointype = node->join.jointype;
 309         nlstate->js.joinqual = (List *)
 310                 ExecInitExpr((Expr *) node->join.joinqual,
 311                                          (PlanState *) nlstate);
 312
 313         /*
 314          * initialize child nodes
 315          *
 316          * Tell the inner child that cheap rescans would be good.  (This is
 317          * unnecessary if we are doing nestloop with inner indexscan, because the
 318          * rescan will always be with a fresh parameter --- but since
 319          * nodeIndexscan doesn't actually care about REWIND, there's no point in
 320          * dealing with that refinement.)
 321          */
 322         outerPlanState(nlstate) = ExecInitNode(outerPlan(node), estate, eflags);
 323         innerPlanState(nlstate) = ExecInitNode(innerPlan(node), estate,
 324                                                                                    eflags | EXEC_FLAG_REWIND);
 325
 326 #define NESTLOOP_NSLOTS 2
 327
 328         /*
 329          * tuple table initialization
 330          */
 331         ExecInitResultTupleSlot(estate, &nlstate->js.ps);
 332
 333         switch (node->join.jointype)
 334         {
 335                 case JOIN_INNER:
 336                 case JOIN_IN:
 337                         break;
 338                 case JOIN_LEFT:
 339                         nlstate->nl_NullInnerTupleSlot =
 340                                 ExecInitNullTupleSlot(estate,
 341                                                                  ExecGetResultType(innerPlanState(nlstate)));
 342                         break;
 343                 default:
 344                         elog(ERROR, "unrecognized join type: %d",
 345                                  (int) node->join.jointype);
 346         }
 347
 348         /*
 349          * initialize tuple type and projection info
 350          */
 351         ExecAssignResultTypeFromTL(&nlstate->js.ps);
 352         ExecAssignProjectionInfo(&nlstate->js.ps, NULL);
 353
 354         /*
 355          * finally, wipe the current outer tuple clean.
 356          */
 357         nlstate->js.ps.ps_OuterTupleSlot = NULL;
 358         nlstate->js.ps.ps_TupFromTlist = false;
 359         nlstate->nl_NeedNewOuter = true;
 360         nlstate->nl_MatchedOuter = false;
 361
 362         NL1_printf("ExecInitNestLoop: %s\n",
 363                            "node initialized");
 364
 365         return nlstate;
 366 }
 367
 368 int
 369 ExecCountSlotsNestLoop(NestLoop *node)
 370 {
 371         return ExecCountSlotsNode(outerPlan(node)) +
 372                 ExecCountSlotsNode(innerPlan(node)) +
 373                 NESTLOOP_NSLOTS;
 374 }
 375
 376 /* ----------------------------------------------------------------
 377  *              ExecEndNestLoop
 378  *
 379  *              closes down scans and frees allocated storage
 380  * ----------------------------------------------------------------
 381  */
 382 void
 383 ExecEndNestLoop(NestLoopState *node)
 384 {
 385         NL1_printf("ExecEndNestLoop: %s\n",
 386                            "ending node processing");
 387
 388         /*
 389          * Free the exprcontext
 390          */
 391         ExecFreeExprContext(&node->js.ps);
 392
 393         /*
 394          * clean out the tuple table
 395          */
 396         ExecClearTuple(node->js.ps.ps_ResultTupleSlot);
 397
 398         /*
 399          * close down subplans
 400          */
 401         ExecEndNode(outerPlanState(node));
 402         ExecEndNode(innerPlanState(node));
 403
 404         NL1_printf("ExecEndNestLoop: %s\n",
 405                            "node processing ended");
 406 }
 407
 408 /* ----------------------------------------------------------------
 409  *              ExecReScanNestLoop
 410  * ----------------------------------------------------------------
 411  */
 412 void
 413 ExecReScanNestLoop(NestLoopState *node, ExprContext *exprCtxt)
 414 {
 415         PlanState  *outerPlan = outerPlanState(node);
 416
 417         /*
 418          * If outerPlan->chgParam is not null then plan will be automatically
 419          * re-scanned by first ExecProcNode. innerPlan is re-scanned for each new
 420          * outer tuple and MUST NOT be re-scanned from here or you'll get troubles
 421          * from inner index scans when outer Vars are used as run-time keys...
 422          */
 423         if (outerPlan->chgParam == NULL)
 424                 ExecReScan(outerPlan, exprCtxt);
 425
 426         /* let outerPlan to free its result tuple ... */
 427         node->js.ps.ps_OuterTupleSlot = NULL;
 428         node->js.ps.ps_TupFromTlist = false;
 429         node->nl_NeedNewOuter = true;
 430         node->nl_MatchedOuter = false;
 431 }