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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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14
src/backend/optimizer/path/tidpath.c
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@ -12,6 +12,12 @@
* this allows
* WHERE ctid IN (tid1, tid2, ...)
*
* We also support "WHERE CURRENT OF cursor" conditions (CurrentOfExpr),
* which amount to "CTID = run-time-determined-TID". These could in
* theory be translated to a simple comparison of CTID to the result of
* a function, but in practice it works better to keep the special node
* representation all the way through to execution.
*
* There is currently no special support for joins involving CTID; in
* particular nothing corresponding to best_inner_indexscan(). Since it's
* not very useful to store TIDs of one table in another table, there
@ -24,7 +30,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/tidpath.c,v 1.29 2007/01/05 22:19:31 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/tidpath.c,v 1.30 2007/06/11 01:16:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -174,6 +180,12 @@ TidQualFromExpr(Node *expr, int varno)
if (IsTidEqualAnyClause((ScalarArrayOpExpr *) expr, varno))
rlst = list_make1(expr);
}
else if (expr && IsA(expr, CurrentOfExpr))
{
/* another base case: check for CURRENT OF on this rel */
if (((CurrentOfExpr *) expr)->cvarno == varno)
rlst = list_make1(expr);
}
else if (and_clause(expr))
{
foreach(l, ((BoolExpr *) expr)->args)