#include "optimizer/var.h"
#include "utils/lsyscache.h"
+/* Local functions */
+static Relids find_placeholders_recurse(PlannerInfo *root, Node *jtnode);
+static void find_placeholders_in_qual(PlannerInfo *root, Node *qual,
+ Relids relids);
+
/*
* make_placeholder_expr
* find_placeholder_info
* Fetch the PlaceHolderInfo for the given PHV; create it if not found
*
+ * This is separate from make_placeholder_expr because subquery pullup has
+ * to make PlaceHolderVars for expressions that might not be used at all in
+ * the upper query, or might not remain after const-expression simplification.
+ * We build PlaceHolderInfos only for PHVs that are still present in the
+ * simplified query passed to query_planner().
+ *
* Note: this should only be called after query_planner() has started.
*/
PlaceHolderInfo *
phinfo->phid = phv->phid;
phinfo->ph_var = copyObject(phv);
phinfo->ph_eval_at = pull_varnos((Node *) phv);
- /* ph_eval_at may change later, see fix_placeholder_eval_levels */
+ /* ph_eval_at may change later, see update_placeholder_eval_levels */
phinfo->ph_needed = NULL; /* initially it's unused */
+ phinfo->ph_may_need = NULL;
/* for the moment, estimate width using just the datatype info */
phinfo->ph_width = get_typavgwidth(exprType((Node *) phv->phexpr),
exprTypmod((Node *) phv->phexpr));
}
/*
- * fix_placeholder_eval_levels
+ * find_placeholders_in_jointree
+ * Search the jointree for PlaceHolderVars, and build PlaceHolderInfos
+ *
+ * We don't need to look at the targetlist because build_base_rel_tlists()
+ * will already have made entries for any PHVs in the tlist.
+ */
+void
+find_placeholders_in_jointree(PlannerInfo *root)
+{
+ /* We need do nothing if the query contains no PlaceHolderVars */
+ if (root->glob->lastPHId != 0)
+ {
+ /* Start recursion at top of jointree */
+ Assert(root->parse->jointree != NULL &&
+ IsA(root->parse->jointree, FromExpr));
+ (void) find_placeholders_recurse(root, (Node *) root->parse->jointree);
+ }
+}
+
+/*
+ * find_placeholders_recurse
+ * One recursion level of find_placeholders_in_jointree.
+ *
+ * jtnode is the current jointree node to examine.
+ *
+ * The result is the set of base Relids contained in or below jtnode.
+ * This is just an internal convenience, it's not used at the top level.
+ */
+static Relids
+find_placeholders_recurse(PlannerInfo *root, Node *jtnode)
+{
+ Relids jtrelids;
+
+ if (jtnode == NULL)
+ return NULL;
+ if (IsA(jtnode, RangeTblRef))
+ {
+ int varno = ((RangeTblRef *) jtnode)->rtindex;
+
+ /* No quals to deal with, just return correct result */
+ jtrelids = bms_make_singleton(varno);
+ }
+ else if (IsA(jtnode, FromExpr))
+ {
+ FromExpr *f = (FromExpr *) jtnode;
+ ListCell *l;
+
+ /*
+ * First, recurse to handle child joins, and form their relid set.
+ */
+ jtrelids = NULL;
+ foreach(l, f->fromlist)
+ {
+ Relids sub_relids;
+
+ sub_relids = find_placeholders_recurse(root, lfirst(l));
+ jtrelids = bms_join(jtrelids, sub_relids);
+ }
+
+ /*
+ * Now process the top-level quals.
+ */
+ find_placeholders_in_qual(root, f->quals, jtrelids);
+ }
+ else if (IsA(jtnode, JoinExpr))
+ {
+ JoinExpr *j = (JoinExpr *) jtnode;
+ Relids leftids,
+ rightids;
+
+ /*
+ * First, recurse to handle child joins, and form their relid set.
+ */
+ leftids = find_placeholders_recurse(root, j->larg);
+ rightids = find_placeholders_recurse(root, j->rarg);
+ jtrelids = bms_join(leftids, rightids);
+
+ /* Process the qual clauses */
+ find_placeholders_in_qual(root, j->quals, jtrelids);
+ }
+ else
+ {
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
+ jtrelids = NULL; /* keep compiler quiet */
+ }
+ return jtrelids;
+}
+
+/*
+ * find_placeholders_in_qual
+ * Process a qual clause for find_placeholders_in_jointree.
+ *
+ * relids is the syntactic join level to mark as the "maybe needed" level
+ * for each PlaceHolderVar found in the qual clause.
+ */
+static void
+find_placeholders_in_qual(PlannerInfo *root, Node *qual, Relids relids)
+{
+ List *vars;
+ ListCell *vl;
+
+ /*
+ * pull_var_clause does more than we need here, but it'll do and it's
+ * convenient to use.
+ */
+ vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
+ foreach(vl, vars)
+ {
+ PlaceHolderVar *phv = (PlaceHolderVar *) lfirst(vl);
+ PlaceHolderInfo *phinfo;
+
+ /* Ignore any plain Vars */
+ if (!IsA(phv, PlaceHolderVar))
+ continue;
+
+ /* Create a PlaceHolderInfo entry if there's not one already */
+ phinfo = find_placeholder_info(root, phv);
+
+ /* Mark the PHV as possibly needed at the qual's syntactic level */
+ phinfo->ph_may_need = bms_add_members(phinfo->ph_may_need, relids);
+
+ /*
+ * This is a bit tricky: the PHV's contained expression may contain
+ * other, lower-level PHVs. We need to get those into the
+ * PlaceHolderInfo list, but they aren't going to be needed where the
+ * outer PHV is referenced. Rather, they'll be needed where the outer
+ * PHV is evaluated. We can estimate that (conservatively) as the
+ * syntactic location of the PHV's expression. Recurse to take care
+ * of any such PHVs.
+ */
+ find_placeholders_in_qual(root, (Node *) phv->phexpr, phv->phrels);
+ }
+ list_free(vars);
+}
+
+/*
+ * update_placeholder_eval_levels
* Adjust the target evaluation levels for placeholders
*
* The initial eval_at level set by find_placeholder_info was the set of
- * rels used in the placeholder's expression (or the whole subselect if
- * the expr is variable-free). If the subselect contains any outer joins
- * that can null any of those rels, we must delay evaluation to above those
- * joins.
+ * rels used in the placeholder's expression (or the whole subselect below
+ * the placeholder's syntactic location, if the expr is variable-free).
+ * If the subselect contains any outer joins that can null any of those rels,
+ * we must delay evaluation to above those joins.
+ *
+ * We repeat this operation each time we add another outer join to
+ * root->join_info_list. It's somewhat annoying to have to do that, but
+ * since we don't have very much information on the placeholders' locations,
+ * it's hard to avoid. Each placeholder's eval_at level must be correct
+ * by the time it starts to figure in outer-join delay decisions for higher
+ * outer joins.
*
* In future we might want to put additional policy/heuristics here to
* try to determine an optimal evaluation level. The current rules will
- * result in evaluation at the lowest possible level.
+ * result in evaluation at the lowest possible level. However, pushing a
+ * placeholder eval up the tree is likely to further constrain evaluation
+ * order for outer joins, so it could easily be counterproductive; and we
+ * don't have enough information at this point to make an intelligent choice.
*/
void
-fix_placeholder_eval_levels(PlannerInfo *root)
+update_placeholder_eval_levels(PlannerInfo *root, SpecialJoinInfo *new_sjinfo)
{
ListCell *lc1;
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc1);
Relids syn_level = phinfo->ph_var->phrels;
- Relids eval_at = phinfo->ph_eval_at;
+ Relids eval_at;
bool found_some;
ListCell *lc2;
+ /*
+ * We don't need to do any work on this placeholder unless the
+ * newly-added outer join is syntactically beneath its location.
+ */
+ if (!bms_is_subset(new_sjinfo->syn_lefthand, syn_level) ||
+ !bms_is_subset(new_sjinfo->syn_righthand, syn_level))
+ continue;
+
/*
* Check for delays due to lower outer joins. This is the same logic
* as in check_outerjoin_delay in initsplan.c, except that we don't
- * want to modify the delay_upper_joins flags; that was all handled
- * already during distribute_qual_to_rels.
+ * have anything to do with the delay_upper_joins flags; delay of
+ * upper outer joins will be handled later, based on the eval_at
+ * values we compute now.
*/
+ eval_at = phinfo->ph_eval_at;
+
do
{
found_some = false;
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc2);
- /* disregard joins not within the expr's sub-select */
+ /* disregard joins not within the PHV's sub-select */
if (!bms_is_subset(sjinfo->syn_lefthand, syn_level) ||
!bms_is_subset(sjinfo->syn_righthand, syn_level))
continue;
} while (found_some);
phinfo->ph_eval_at = eval_at;
+ }
+}
- /*
- * Now that we know where to evaluate the placeholder, make sure that
- * any vars or placeholders it uses will be available at that join
- * level. NOTE: this could cause more PlaceHolderInfos to be added to
- * placeholder_list. That is okay because we'll process them before
- * falling out of the foreach loop. Also, it could cause the
- * ph_needed sets of existing list entries to expand, which is also
- * okay because this loop doesn't examine those.
- */
+/*
+ * fix_placeholder_input_needed_levels
+ * Adjust the "needed at" levels for placeholder inputs
+ *
+ * This is called after we've finished determining the eval_at levels for
+ * all placeholders. We need to make sure that all vars and placeholders
+ * needed to evaluate each placeholder will be available at the join level
+ * where the evaluation will be done. Note that this loop can have
+ * side-effects on the ph_needed sets of other PlaceHolderInfos; that's okay
+ * because we don't examine ph_needed here, so there are no ordering issues
+ * to worry about.
+ */
+void
+fix_placeholder_input_needed_levels(PlannerInfo *root)
+{
+ ListCell *lc;
+
+ foreach(lc, root->placeholder_list)
+ {
+ PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
+ Relids eval_at = phinfo->ph_eval_at;
+
+ /* No work unless it'll be evaluated above baserel level */
if (bms_membership(eval_at) == BMS_MULTIPLE)
{
List *vars = pull_var_clause((Node *) phinfo->ph_var->phexpr,
* Add any required PlaceHolderVars to base rels' targetlists.
*
* If any placeholder can be computed at a base rel and is needed above it,
- * add it to that rel's targetlist. We have to do this separately from
- * fix_placeholder_eval_levels() because join removal happens in between,
- * and can change the ph_eval_at sets. There is essentially the same logic
- * in add_placeholders_to_joinrel, but we can't do that part until joinrels
- * are formed.
+ * add it to that rel's targetlist. This might look like it could be merged
+ * with fix_placeholder_input_needed_levels, but it must be separate because
+ * join removal happens in between, and can change the ph_eval_at sets. There
+ * is essentially the same logic in add_placeholders_to_joinrel, but we can't
+ * do that part until joinrels are formed.
*/
void
add_placeholders_to_base_rels(PlannerInfo *root)
projects / users / c2main / postgres.git / commitdiff