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Fix set_append_rel_pathlist() to deal intelligently with cases where

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substituting a child rel's output expressions into the appendrel's restriction
clauses yields a pseudoconstant restriction.  We might be able to skip scanning
that child rel entirely (if we get constant FALSE), or generate a one-time
filter.  8.3 more or less accidentally generated plans that weren't completely
stupid in these cases, but that was only because an extra recursive level of
subquery_planner() always occurred and allowed const-simplification to happen.
8.4's ability to pull up appendrel members with non-Var outputs exposes the
fact that we need to work harder here.  Per gripe from Sergey Burladyan.
This commit is contained in:
Tom Lane
2009-07-06 18:26:30 +00:00
parent bf6570abef
commit 9b27eab71c
4 changed files with 114 additions and 58 deletions
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54
src/backend/optimizer/prep/prepunion.c
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@@ -22,7 +22,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.171 2009/06/11 14:48:59 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.172 2009/07/06 18:26:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1636,57 +1636,7 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
Assert(!IsA(node, SpecialJoinInfo));
Assert(!IsA(node, AppendRelInfo));
Assert(!IsA(node, PlaceHolderInfo));
/*
* We have to process RestrictInfo nodes specially.
*/
if (IsA(node, RestrictInfo))
{
RestrictInfo *oldinfo = (RestrictInfo *) node;
RestrictInfo *newinfo = makeNode(RestrictInfo);
/* Copy all flat-copiable fields */
memcpy(newinfo, oldinfo, sizeof(RestrictInfo));
/* Recursively fix the clause itself */
newinfo->clause = (Expr *)
adjust_appendrel_attrs_mutator((Node *) oldinfo->clause, context);
/* and the modified version, if an OR clause */
newinfo->orclause = (Expr *)
adjust_appendrel_attrs_mutator((Node *) oldinfo->orclause, context);
/* adjust relid sets too */
newinfo->clause_relids = adjust_relid_set(oldinfo->clause_relids,
context->parent_relid,
context->child_relid);
newinfo->required_relids = adjust_relid_set(oldinfo->required_relids,
context->parent_relid,
context->child_relid);
newinfo->left_relids = adjust_relid_set(oldinfo->left_relids,
context->parent_relid,
context->child_relid);
newinfo->right_relids = adjust_relid_set(oldinfo->right_relids,
context->parent_relid,
context->child_relid);
/*
* Reset cached derivative fields, since these might need to have
* different values when considering the child relation.
*/
newinfo->eval_cost.startup = -1;
newinfo->norm_selec = -1;
newinfo->outer_selec = -1;
newinfo->left_ec = NULL;
newinfo->right_ec = NULL;
newinfo->left_em = NULL;
newinfo->right_em = NULL;
newinfo->scansel_cache = NIL;
newinfo->left_bucketsize = -1;
newinfo->right_bucketsize = -1;
return (Node *) newinfo;
}
Assert(!IsA(node, RestrictInfo));
/*
* NOTE: we do not need to recurse into sublinks, because they should