Fix UPDATE/DELETE WHERE CURRENT OF to support repeated update and update-
then-delete on the current cursor row. The basic fix is that nodeTidscan.c has to apply heap_get_latest_tid() to the current-scan-TID obtained from the cursor query; this ensures we get the latest row version to work with. However, since that only works if the query plan is a TID scan, we also have to hack the planner to make sure only that type of plan will be selected. (Formerly, the planner might decide to apply a seqscan if the table is very small. This change is probably a Good Thing anyway, since it's hard to see how a seqscan could really win.) That means the execQual.c code to support CurrentOfExpr as a regular expression type is dead code, so replace it with just an elog(). Also, add regression tests covering these cases. Note that the added tests expose the fact that re-fetching an updated row misbehaves if the cursor used FOR UPDATE. That's an independent bug that should be fixed later. Per report from Dharmendra Goyal.
This commit is contained in:
Tom Lane
parent
9226ba817b
commit
c29a9c37bf
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.222 2007/09/06 17:31:58 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.223 2007/10/24 18:37:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -3694,45 +3694,17 @@ ExecEvalArrayCoerceExpr(ArrayCoerceExprState *astate,
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/* ----------------------------------------------------------------
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* ExecEvalCurrentOfExpr
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*
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* Normally, the planner will convert CURRENT OF into a TidScan qualification,
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* but we have plain execQual support in case it doesn't.
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* The planner must convert CURRENT OF into a TidScan qualification.
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* So, we have to be able to do ExecInitExpr on a CurrentOfExpr,
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* but we shouldn't ever actually execute it.
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* ----------------------------------------------------------------
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*/
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static Datum
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ExecEvalCurrentOfExpr(ExprState *exprstate, ExprContext *econtext,
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bool *isNull, ExprDoneCond *isDone)
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{
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CurrentOfExpr *cexpr = (CurrentOfExpr *) exprstate->expr;
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bool result;
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bool lisnull;
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Oid tableoid;
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ItemPointer tuple_tid;
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ItemPointerData cursor_tid;
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if (isDone)
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*isDone = ExprSingleResult;
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*isNull = false;
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Assert(cexpr->cvarno != INNER);
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Assert(cexpr->cvarno != OUTER);
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Assert(!TupIsNull(econtext->ecxt_scantuple));
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/* Use slot_getattr to catch any possible mistakes */
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tableoid = DatumGetObjectId(slot_getattr(econtext->ecxt_scantuple,
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TableOidAttributeNumber,
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&lisnull));
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Assert(!lisnull);
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tuple_tid = (ItemPointer)
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DatumGetPointer(slot_getattr(econtext->ecxt_scantuple,
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SelfItemPointerAttributeNumber,
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&lisnull));
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Assert(!lisnull);
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if (execCurrentOf(cexpr, econtext, tableoid, &cursor_tid))
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result = ItemPointerEquals(&cursor_tid, tuple_tid);
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else
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result = false;
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return BoolGetDatum(result);
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elog(ERROR, "CURRENT OF cannot be executed");
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return 0; /* keep compiler quiet */
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}
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.55 2007/06/11 22:22:40 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/executor/nodeTidscan.c,v 1.56 2007/10/24 18:37:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -68,6 +68,7 @@ TidListCreate(TidScanState *tidstate)
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tidList = (ItemPointerData *)
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palloc(numAllocTids * sizeof(ItemPointerData));
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numTids = 0;
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tidstate->tss_isCurrentOf = false;
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foreach(l, evalList)
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{
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@ -165,6 +166,7 @@ TidListCreate(TidScanState *tidstate)
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numAllocTids * sizeof(ItemPointerData));
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}
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tidList[numTids++] = cursor_tid;
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tidstate->tss_isCurrentOf = true;
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}
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}
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else
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@ -182,6 +184,9 @@ TidListCreate(TidScanState *tidstate)
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int lastTid;
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int i;
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/* CurrentOfExpr could never appear OR'd with something else */
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Assert(!tidstate->tss_isCurrentOf);
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qsort((void *) tidList, numTids, sizeof(ItemPointerData),
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itemptr_comparator);
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lastTid = 0;
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@ -269,7 +274,8 @@ TidNext(TidScanState *node)
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/*
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* XXX shouldn't we check here to make sure tuple matches TID list? In
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* runtime-key case this is not certain, is it?
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* runtime-key case this is not certain, is it? However, in the
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* WHERE CURRENT OF case it might not match anyway ...
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*/
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ExecStoreTuple(estate->es_evTuple[scanrelid - 1],
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@ -319,6 +325,15 @@ TidNext(TidScanState *node)
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while (node->tss_TidPtr >= 0 && node->tss_TidPtr < numTids)
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{
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tuple->t_self = tidList[node->tss_TidPtr];
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/*
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* For WHERE CURRENT OF, the tuple retrieved from the cursor might
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* since have been updated; if so, we should fetch the version that
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* is current according to our snapshot.
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*/
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if (node->tss_isCurrentOf)
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heap_get_latest_tid(heapRelation, snapshot, &tuple->t_self);
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if (heap_fetch(heapRelation, snapshot, tuple, &buffer, false, NULL))
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{
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/*
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@ -54,7 +54,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.186 2007/09/22 21:36:40 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.187 2007/10/24 18:37:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -769,6 +769,7 @@ cost_tidscan(Path *path, PlannerInfo *root,
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{
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Cost startup_cost = 0;
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Cost run_cost = 0;
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bool isCurrentOf = false;
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Cost cpu_per_tuple;
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QualCost tid_qual_cost;
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int ntuples;
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@ -778,9 +779,6 @@ cost_tidscan(Path *path, PlannerInfo *root,
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Assert(baserel->relid > 0);
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Assert(baserel->rtekind == RTE_RELATION);
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if (!enable_tidscan)
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startup_cost += disable_cost;
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/* Count how many tuples we expect to retrieve */
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ntuples = 0;
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foreach(l, tidquals)
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@ -793,6 +791,12 @@ cost_tidscan(Path *path, PlannerInfo *root,
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ntuples += estimate_array_length(arraynode);
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}
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else if (IsA(lfirst(l), CurrentOfExpr))
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{
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/* CURRENT OF yields 1 tuple */
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isCurrentOf = true;
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ntuples++;
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}
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else
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{
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/* It's just CTID = something, count 1 tuple */
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@ -800,6 +804,22 @@ cost_tidscan(Path *path, PlannerInfo *root,
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}
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}
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/*
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* We must force TID scan for WHERE CURRENT OF, because only nodeTidscan.c
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* understands how to do it correctly. Therefore, honor enable_tidscan
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* only when CURRENT OF isn't present. Also note that cost_qual_eval
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* counts a CurrentOfExpr as having startup cost disable_cost, which we
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* subtract off here; that's to prevent other plan types such as seqscan
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* from winning.
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*/
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if (isCurrentOf)
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{
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Assert(baserel->baserestrictcost.startup >= disable_cost);
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startup_cost -= disable_cost;
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}
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else if (!enable_tidscan)
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startup_cost += disable_cost;
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/*
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* The TID qual expressions will be computed once, any other baserestrict
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* quals once per retrived tuple.
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@ -2002,8 +2022,8 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
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}
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else if (IsA(node, CurrentOfExpr))
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{
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/* This is noticeably more expensive than a typical operator */
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context->total.per_tuple += 100 * cpu_operator_cost;
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/* Report high cost to prevent selection of anything but TID scan */
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context->total.startup += disable_cost;
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}
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else if (IsA(node, SubLink))
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{
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.178 2007/09/20 17:56:32 tgl Exp $
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* $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.179 2007/10/24 18:37:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1087,6 +1087,7 @@ typedef struct BitmapHeapScanState
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/* ----------------
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* TidScanState information
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*
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* isCurrentOf scan has a CurrentOfExpr qual
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* NumTids number of tids in this scan
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* TidPtr index of currently fetched tid
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* TidList evaluated item pointers (array of size NumTids)
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@ -1096,6 +1097,7 @@ typedef struct TidScanState
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{
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ScanState ss; /* its first field is NodeTag */
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List *tss_tidquals; /* list of ExprState nodes */
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bool tss_isCurrentOf;
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int tss_NumTids;
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int tss_TidPtr;
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int tss_MarkTidPtr;
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@ -982,6 +982,139 @@ SELECT * FROM uctest;
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8 | one
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(2 rows)
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-- Check repeated-update and update-then-delete cases
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BEGIN;
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DECLARE c1 CURSOR FOR SELECT * FROM uctest;
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FETCH c1;
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f1 | f2
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----+-------
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3 | three
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(1 row)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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8 | one
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13 | three
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(2 rows)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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8 | one
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23 | three
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(2 rows)
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-- insensitive cursor should not show effects of updates or deletes
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FETCH RELATIVE 0 FROM c1;
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f1 | f2
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----+-------
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3 | three
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(1 row)
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DELETE FROM uctest WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-----
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8 | one
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(1 row)
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DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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f1 | f2
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----+-----
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8 | one
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(1 row)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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f1 | f2
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----+-----
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8 | one
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(1 row)
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FETCH RELATIVE 0 FROM c1;
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f1 | f2
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----+-------
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3 | three
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(1 row)
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ROLLBACK;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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3 | three
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8 | one
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(2 rows)
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BEGIN;
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DECLARE c1 CURSOR FOR SELECT * FROM uctest FOR UPDATE;
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FETCH c1;
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f1 | f2
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----+-------
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3 | three
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(1 row)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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8 | one
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13 | three
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(2 rows)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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8 | one
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23 | three
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(2 rows)
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-- sensitive cursor should show effects of updates or deletes
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-- XXX current behavior is WRONG
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FETCH RELATIVE 0 FROM c1;
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f1 | f2
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----+-----
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8 | one
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(1 row)
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DELETE FROM uctest WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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23 | three
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(1 row)
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DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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23 | three
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(1 row)
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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23 | three
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(1 row)
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FETCH RELATIVE 0 FROM c1;
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f1 | f2
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----+----
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(0 rows)
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ROLLBACK;
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SELECT * FROM uctest;
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f1 | f2
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----+-------
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3 | three
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8 | one
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(2 rows)
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-- Check inheritance cases
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CREATE TEMP TABLE ucchild () inherits (uctest);
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INSERT INTO ucchild values(100, 'hundred');
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@ -349,6 +349,46 @@ SELECT * FROM uctest;
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COMMIT;
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SELECT * FROM uctest;
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-- Check repeated-update and update-then-delete cases
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BEGIN;
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DECLARE c1 CURSOR FOR SELECT * FROM uctest;
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FETCH c1;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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-- insensitive cursor should not show effects of updates or deletes
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FETCH RELATIVE 0 FROM c1;
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DELETE FROM uctest WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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FETCH RELATIVE 0 FROM c1;
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ROLLBACK;
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SELECT * FROM uctest;
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BEGIN;
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DECLARE c1 CURSOR FOR SELECT * FROM uctest FOR UPDATE;
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FETCH c1;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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-- sensitive cursor should show effects of updates or deletes
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-- XXX current behavior is WRONG
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FETCH RELATIVE 0 FROM c1;
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DELETE FROM uctest WHERE CURRENT OF c1;
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SELECT * FROM uctest;
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DELETE FROM uctest WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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UPDATE uctest SET f1 = f1 + 10 WHERE CURRENT OF c1; -- no-op
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SELECT * FROM uctest;
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FETCH RELATIVE 0 FROM c1;
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ROLLBACK;
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SELECT * FROM uctest;
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-- Check inheritance cases
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CREATE TEMP TABLE ucchild () inherits (uctest);
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INSERT INTO ucchild values(100, 'hundred');
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