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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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42
src/backend/optimizer/util/var.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.69 2007/01/05 22:19:33 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.70 2007/06/11 01:16:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -111,6 +111,14 @@ pull_varnos_walker(Node *node, pull_varnos_context *context)
context->varnos = bms_add_member(context->varnos, var->varno);
return false;
}
if (IsA(node, CurrentOfExpr))
{
CurrentOfExpr *cexpr = (CurrentOfExpr *) node;
if (context->sublevels_up == 0)
context->varnos = bms_add_member(context->varnos, cexpr->cvarno);
return false;
}
if (IsA(node, Query))
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
@ -217,6 +225,8 @@ contain_var_clause_walker(Node *node, void *context)
return true; /* abort the tree traversal and return true */
return false;
}
if (IsA(node, CurrentOfExpr))
return true;
return expression_tree_walker(node, contain_var_clause_walker, context);
}
@ -249,6 +259,13 @@ contain_vars_of_level_walker(Node *node, int *sublevels_up)
{
if (((Var *) node)->varlevelsup == *sublevels_up)
return true; /* abort tree traversal and return true */
return false;
}
if (IsA(node, CurrentOfExpr))
{
if (*sublevels_up == 0)
return true;
return false;
}
if (IsA(node, Query))
{
@ -376,6 +393,29 @@ find_minimum_var_level_walker(Node *node,
}
}
}
if (IsA(node, CurrentOfExpr))
{
int varlevelsup = 0;
/* convert levelsup to frame of reference of original query */
varlevelsup -= context->sublevels_up;
/* ignore local vars of subqueries */
if (varlevelsup >= 0)
{
if (context->min_varlevel < 0 ||
context->min_varlevel > varlevelsup)
{
context->min_varlevel = varlevelsup;
/*
* As soon as we find a local variable, we can abort the tree
* traversal, since min_varlevel is then certainly 0.
*/
if (varlevelsup == 0)
return true;
}
}
}
/*
* An Aggref must be treated like a Var of its level. Normally we'd get