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Support UPDATE/DELETE WHERE CURRENT OF cursor_name, per SQL standard.

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Along the way, allow FOR UPDATE in non-WITH-HOLD cursors; there may once
have been a reason to disallow that, but it seems to work now, and it's
really rather necessary if you want to select a row via a cursor and then
update it in a concurrent-safe fashion.

Original patch by Arul Shaji, rather heavily editorialized by Tom Lane.
This commit is contained in:
Tom Lane
2007-06-11 01:16:30 +00:00
parent 85d72f0516
commit 6808f1b1de
30 changed files with 940 additions and 127 deletions
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43
src/backend/executor/execQual.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.218 2007/06/05 21:31:04 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.219 2007/06/11 01:16:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -151,6 +151,8 @@ static Datum ExecEvalCoerceViaIO(CoerceViaIOState *iostate,
static Datum ExecEvalArrayCoerceExpr(ArrayCoerceExprState *astate,
ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCurrentOfExpr(ExprState *exprstate, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
/* ----------------------------------------------------------------
@ -3618,6 +3620,41 @@ ExecEvalArrayCoerceExpr(ArrayCoerceExprState *astate,
astate->amstate);
}
/* ----------------------------------------------------------------
* ExecEvalCurrentOfExpr
*
* Normally, the planner will convert CURRENT OF into a TidScan qualification,
* but we have plain execQual support in case it doesn't.
* ----------------------------------------------------------------
*/
static Datum
ExecEvalCurrentOfExpr(ExprState *exprstate, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone)
{
CurrentOfExpr *cexpr = (CurrentOfExpr *) exprstate->expr;
bool result;
HeapTuple tup;
ItemPointerData cursor_tid;
if (isDone)
*isDone = ExprSingleResult;
*isNull = false;
Assert(cexpr->cvarno != INNER);
Assert(cexpr->cvarno != OUTER);
Assert(!TupIsNull(econtext->ecxt_scantuple));
tup = econtext->ecxt_scantuple->tts_tuple;
if (tup == NULL)
elog(ERROR, "CURRENT OF applied to non-materialized tuple");
if (execCurrentOf(cexpr->cursor_name, tup->t_tableOid, &cursor_tid))
result = ItemPointerEquals(&cursor_tid, &(tup->t_self));
else
result = false;
return BoolGetDatum(result);
}
/*
* ExecEvalExprSwitchContext
@ -4266,6 +4303,10 @@ ExecInitExpr(Expr *node, PlanState *parent)
state = (ExprState *) cstate;
}
break;
case T_CurrentOfExpr:
state = (ExprState *) makeNode(ExprState);
state->evalfunc = ExecEvalCurrentOfExpr;
break;
case T_TargetEntry:
{
TargetEntry *tle = (TargetEntry *) node;