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Fix ruleutils' get_variable() to print something useful for Vars referencing 

resjunk outputs of subquery tlists, instead of throwing an error.  Per bug
#5548 from Daniel Grace.

We might at some point find we ought to back-patch this further than 9.0,
but I think that such Vars can only occur as resjunk members of upper-level
tlists, in which case the problem can't arise because prior versions didn't
print resjunk tlist items in EXPLAIN VERBOSE.
This commit is contained in:
Tom Lane 2010-07-09 21:11:47 +00:00
parent a0d7c5f689
commit 2b8a624596
1 changed files with 44 additions and 1 deletions
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45
src/backend/utils/adt/ruleutils.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.326 2010/05/30 18:10:41 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.327 2010/07/09 21:11:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -3637,6 +3637,49 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
return NULL; /* keep compiler quiet */
}
/*
* The planner will sometimes emit Vars referencing resjunk elements of a
* subquery's target list (this is currently only possible if it chooses
* to generate a "physical tlist" for a SubqueryScan or CteScan node).
* Although we prefer to print subquery-referencing Vars using the
* subquery's alias, that's not possible for resjunk items since they have
* no alias. So in that case, drill down to the subplan and print the
* contents of the referenced tlist item. This works because in a plan
* tree, such Vars can only occur in a SubqueryScan or CteScan node,
* and we'll have set dpns->inner_plan to reference the child plan node.
*/
if ((rte->rtekind == RTE_SUBQUERY || rte->rtekind == RTE_CTE) &&
attnum > list_length(rte->eref->colnames) &&
dpns->inner_plan)
{
TargetEntry *tle;
Plan *save_outer;
Plan *save_inner;
tle = get_tle_by_resno(dpns->inner_plan->targetlist, var->varattno);
if (!tle)
elog(ERROR, "bogus varattno for subquery var: %d", var->varattno);
Assert(netlevelsup == 0);
save_outer = dpns->outer_plan;
save_inner = dpns->inner_plan;
push_plan(dpns, dpns->inner_plan);
/*
* Force parentheses because our caller probably assumed a Var is a
* simple expression.
*/
if (!IsA(tle->expr, Var))
appendStringInfoChar(buf, '(');
get_rule_expr((Node *) tle->expr, context, true);
if (!IsA(tle->expr, Var))
appendStringInfoChar(buf, ')');
dpns->outer_plan = save_outer;
dpns->inner_plan = save_inner;
return NULL;
}
/* Identify names to use */
schemaname = NULL; /* default assumptions */
refname = rte->eref->aliasname;