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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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20
src/backend/optimizer/path/costsize.c
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@@ -54,7 +54,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.184 2007/06/05 21:31:05 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.185 2007/06/11 01:16:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -770,6 +770,7 @@ cost_tidscan(Path *path, PlannerInfo *root,
Cost startup_cost = 0;
Cost run_cost = 0;
Cost cpu_per_tuple;
QualCost tid_qual_cost;
int ntuples;
ListCell *l;
@@ -799,12 +800,20 @@ cost_tidscan(Path *path, PlannerInfo *root,
}
}
/*
* The TID qual expressions will be computed once, any other baserestrict
* quals once per retrived tuple.
*/
cost_qual_eval(&tid_qual_cost, tidquals, root);
/* disk costs --- assume each tuple on a different page */
run_cost += random_page_cost * ntuples;
/* CPU costs */
startup_cost += baserel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple;
startup_cost += baserel->baserestrictcost.startup +
tid_qual_cost.per_tuple;
cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple -
tid_qual_cost.per_tuple;
run_cost += cpu_per_tuple * ntuples;
path->startup_cost = startup_cost;
@@ -1991,6 +2000,11 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
cpu_operator_cost;
}
}
else if (IsA(node, CurrentOfExpr))
{
/* This is noticeably more expensive than a typical operator */
context->total.per_tuple += 100 * cpu_operator_cost;
}
else if (IsA(node, SubLink))
{
/* This routine should not be applied to un-planned expressions */