* ExecInitUpdateProjection * Do one-time initialization of projection data for UPDATE tuples. * * UPDATE always needs a projection, because (1) there's always some junk * attrs, and (2) we may need to merge values of not-updated columns from * the old tuple into the final tuple. In UPDATE, the tuple arriving from * the subplan contains only new values for the changed columns, plus row * i
| 519 | * matches the target table (ExecBuildUpdateProjection does that). |
| 520 | */ |
| 521 | static void |
| 522 | ExecInitUpdateProjection(ModifyTableState *mtstate, |
| 523 | ResultRelInfo *resultRelInfo) |
| 524 | { |
| 525 | ModifyTable *node = (ModifyTable *) mtstate->ps.plan; |
| 526 | Plan *subplan = outerPlan(node); |
| 527 | EState *estate = mtstate->ps.state; |
| 528 | TupleDesc relDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc); |
| 529 | int whichrel; |
| 530 | List *updateColnos; |
| 531 | |
| 532 | /* |
| 533 | * Usually, mt_lastResultIndex matches the target rel. If it happens not |
| 534 | * to, we can get the index the hard way with an integer division. |
| 535 | */ |
| 536 | whichrel = mtstate->mt_lastResultIndex; |
| 537 | if (resultRelInfo != mtstate->resultRelInfo + whichrel) |
| 538 | { |
| 539 | whichrel = resultRelInfo - mtstate->resultRelInfo; |
| 540 | Assert(whichrel >= 0 && whichrel < mtstate->mt_nrels); |
| 541 | } |
| 542 | |
| 543 | updateColnos = (List *) list_nth(node->updateColnosLists, whichrel); |
| 544 | |
| 545 | /* |
| 546 | * For UPDATE, we use the old tuple to fill up missing values in the tuple |
| 547 | * produced by the subplan to get the new tuple. We need two slots, both |
| 548 | * matching the table's desired format. |
| 549 | */ |
| 550 | resultRelInfo->ri_oldTupleSlot = |
| 551 | table_slot_create(resultRelInfo->ri_RelationDesc, |
| 552 | &estate->es_tupleTable); |
| 553 | resultRelInfo->ri_newTupleSlot = |
| 554 | table_slot_create(resultRelInfo->ri_RelationDesc, |
| 555 | &estate->es_tupleTable); |
| 556 | |
| 557 | /* need an expression context to do the projection */ |
| 558 | if (mtstate->ps.ps_ExprContext == NULL) |
| 559 | ExecAssignExprContext(estate, &mtstate->ps); |
| 560 | |
| 561 | resultRelInfo->ri_projectNew = |
| 562 | ExecBuildUpdateProjection(subplan->targetlist, |
| 563 | false, /* subplan did the evaluation */ |
| 564 | updateColnos, |
| 565 | relDesc, |
| 566 | mtstate->ps.ps_ExprContext, |
| 567 | resultRelInfo->ri_newTupleSlot, |
| 568 | &mtstate->ps); |
| 569 | |
| 570 | resultRelInfo->ri_projectNewInfoValid = true; |
| 571 | } |
| 572 | |
| 573 | /* |
| 574 | * ExecGetInsertNewTuple |
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