* PlaceHolderVar and PlaceHolderInfo manipulation routines
*
*
- * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/placeholder.c,v 1.8 2010/07/06 19:18:57 momjian Exp $
+ * src/backend/optimizer/util/placeholder.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/nodeFuncs.h"
+#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/placeholder.h"
#include "optimizer/planmain.h"
#include "optimizer/var.h"
#include "utils/lsyscache.h"
+/* Local functions */
+static void find_placeholders_recurse(PlannerInfo *root, Node *jtnode);
+static void find_placeholders_in_expr(PlannerInfo *root, Node *expr);
+
/*
* make_placeholder_expr
/*
* find_placeholder_info
- * Fetch the PlaceHolderInfo for the given PHV; create it if not found
+ * Fetch the PlaceHolderInfo for the given PHV
+ *
+ * If the PlaceHolderInfo doesn't exist yet, create it if create_new_ph is
+ * true, else throw an error.
+ *
+ * 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.
+ * Note: this should only be called after query_planner() has started. Also,
+ * create_new_ph must not be true after deconstruct_jointree begins, because
+ * make_outerjoininfo assumes that we already know about all placeholders.
*/
PlaceHolderInfo *
-find_placeholder_info(PlannerInfo *root, PlaceHolderVar *phv)
+find_placeholder_info(PlannerInfo *root, PlaceHolderVar *phv,
+ bool create_new_ph)
{
PlaceHolderInfo *phinfo;
+ Relids rels_used;
ListCell *lc;
/* if this ever isn't true, we'd need to be able to look in parent lists */
}
/* Not found, so create it */
+ if (!create_new_ph)
+ elog(ERROR, "too late to create a new PlaceHolderInfo");
+
phinfo = makeNode(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 */
+
+ /*
+ * Any referenced rels that are outside the PHV's syntactic scope are
+ * LATERAL references, which should be included in ph_lateral but not in
+ * ph_eval_at. If no referenced rels are within the syntactic scope,
+ * force evaluation at the syntactic location.
+ */
+ rels_used = pull_varnos((Node *) phv->phexpr);
+ phinfo->ph_lateral = bms_difference(rels_used, phv->phrels);
+ if (bms_is_empty(phinfo->ph_lateral))
+ phinfo->ph_lateral = NULL; /* make it exactly NULL if empty */
+ phinfo->ph_eval_at = bms_int_members(rels_used, phv->phrels);
+ /* If no contained vars, force evaluation at syntactic location */
+ if (bms_is_empty(phinfo->ph_eval_at))
+ {
+ phinfo->ph_eval_at = bms_copy(phv->phrels);
+ Assert(!bms_is_empty(phinfo->ph_eval_at));
+ }
+ /* ph_eval_at may change later, see update_placeholder_eval_levels */
phinfo->ph_needed = NULL; /* initially it's unused */
/* for the moment, estimate width using just the datatype info */
phinfo->ph_width = get_typavgwidth(exprType((Node *) phv->phexpr),
root->placeholder_list = lappend(root->placeholder_list, phinfo);
+ /*
+ * The PHV's contained expression may contain other, lower-level PHVs. We
+ * now know we need to get those into the PlaceHolderInfo list, too, so we
+ * may as well do that immediately.
+ */
+ find_placeholders_in_expr(root, (Node *) phinfo->ph_var->phexpr);
+
return phinfo;
}
/*
- * 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.
+ *
+ * This is called before we begin deconstruct_jointree. Once we begin
+ * deconstruct_jointree, all active placeholders must be present in
+ * root->placeholder_list, because make_outerjoininfo and
+ * update_placeholder_eval_levels require this info to be available
+ * while we crawl up the join tree.
+ */
+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));
+ 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.
+ */
+static void
+find_placeholders_recurse(PlannerInfo *root, Node *jtnode)
+{
+ if (jtnode == NULL)
+ return;
+ if (IsA(jtnode, RangeTblRef))
+ {
+ /* No quals to deal with here */
+ }
+ else if (IsA(jtnode, FromExpr))
+ {
+ FromExpr *f = (FromExpr *) jtnode;
+ ListCell *l;
+
+ /*
+ * First, recurse to handle child joins.
+ */
+ foreach(l, f->fromlist)
+ {
+ find_placeholders_recurse(root, lfirst(l));
+ }
+
+ /*
+ * Now process the top-level quals.
+ */
+ find_placeholders_in_expr(root, f->quals);
+ }
+ else if (IsA(jtnode, JoinExpr))
+ {
+ JoinExpr *j = (JoinExpr *) jtnode;
+
+ /*
+ * First, recurse to handle child joins.
+ */
+ find_placeholders_recurse(root, j->larg);
+ find_placeholders_recurse(root, j->rarg);
+
+ /* Process the qual clauses */
+ find_placeholders_in_expr(root, j->quals);
+ }
+ else
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
+}
+
+/*
+ * find_placeholders_in_expr
+ * Find all PlaceHolderVars in the given expression, and create
+ * PlaceHolderInfo entries for them.
+ */
+static void
+find_placeholders_in_expr(PlannerInfo *root, Node *expr)
+{
+ 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(expr,
+ PVC_RECURSE_AGGREGATES |
+ PVC_RECURSE_WINDOWFUNCS |
+ PVC_INCLUDE_PLACEHOLDERS);
+ foreach(vl, vars)
+ {
+ PlaceHolderVar *phv = (PlaceHolderVar *) lfirst(vl);
+
+ /* Ignore any plain Vars */
+ if (!IsA(phv, PlaceHolderVar))
+ continue;
+
+ /* Create a PlaceHolderInfo entry if there's not one already */
+ (void) find_placeholder_info(root, phv, true);
+ }
+ 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 query 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);
+ /* Can't move the PHV's eval_at level to above its syntactic level */
+ Assert(bms_is_subset(eval_at, syn_level));
+
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.
- */
- if (bms_membership(eval_at) == BMS_MULTIPLE)
- {
- List *vars = pull_var_clause((Node *) phinfo->ph_var->phexpr,
- PVC_INCLUDE_PLACEHOLDERS);
+/*
+ * 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 scan or join
+ * level where the evaluation will be done. (It might seem that scan-level
+ * evaluations aren't interesting, but that's not so: a LATERAL reference
+ * within a placeholder's expression needs to cause the referenced var or
+ * placeholder to be marked as needed in the scan where it's evaluated.)
+ * 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;
- add_vars_to_targetlist(root, vars, eval_at);
- list_free(vars);
- }
+ foreach(lc, root->placeholder_list)
+ {
+ PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
+ List *vars = pull_var_clause((Node *) phinfo->ph_var->phexpr,
+ PVC_RECURSE_AGGREGATES |
+ PVC_RECURSE_WINDOWFUNCS |
+ PVC_INCLUDE_PLACEHOLDERS);
+
+ add_vars_to_targetlist(root, vars, phinfo->ph_eval_at, false);
+ list_free(vars);
}
}
* 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)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
Relids eval_at = phinfo->ph_eval_at;
+ int varno;
- if (bms_membership(eval_at) == BMS_SINGLETON)
+ if (bms_get_singleton_member(eval_at, &varno) &&
+ bms_nonempty_difference(phinfo->ph_needed, eval_at))
{
- int varno = bms_singleton_member(eval_at);
RelOptInfo *rel = find_base_rel(root, varno);
- if (bms_nonempty_difference(phinfo->ph_needed, rel->relids))
- rel->reltargetlist = lappend(rel->reltargetlist,
- copyObject(phinfo->ph_var));
+ rel->reltarget->exprs = lappend(rel->reltarget->exprs,
+ copyObject(phinfo->ph_var));
+ /* reltarget's cost and width fields will be updated later */
}
}
}
/*
* add_placeholders_to_joinrel
- * Add any required PlaceHolderVars to a join rel's targetlist.
+ * Add any required PlaceHolderVars to a join rel's targetlist;
+ * and if they contain lateral references, add those references to the
+ * joinrel's direct_lateral_relids.
*
* A join rel should emit a PlaceHolderVar if (a) the PHV is needed above
* this join level and (b) the PHV can be computed at or below this level.
- * At this time we do not need to distinguish whether the PHV will be
- * computed here or copied up from below.
*/
void
-add_placeholders_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel)
+add_placeholders_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
+ RelOptInfo *outer_rel, RelOptInfo *inner_rel)
{
Relids relids = joinrel->relids;
ListCell *lc;
if (bms_is_subset(phinfo->ph_eval_at, relids))
{
/* Yup, add it to the output */
- joinrel->reltargetlist = lappend(joinrel->reltargetlist,
- phinfo->ph_var);
- joinrel->width += phinfo->ph_width;
+ joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs,
+ phinfo->ph_var);
+ joinrel->reltarget->width += phinfo->ph_width;
+
+ /*
+ * Charge the cost of evaluating the contained expression if
+ * the PHV can be computed here but not in either input. This
+ * is a bit bogus because we make the decision based on the
+ * first pair of possible input relations considered for the
+ * joinrel. With other pairs, it might be possible to compute
+ * the PHV in one input or the other, and then we'd be double
+ * charging the PHV's cost for some join paths. For now, live
+ * with that; but we might want to improve it later by
+ * refiguring the reltarget costs for each pair of inputs.
+ */
+ if (!bms_is_subset(phinfo->ph_eval_at, outer_rel->relids) &&
+ !bms_is_subset(phinfo->ph_eval_at, inner_rel->relids))
+ {
+ QualCost cost;
+
+ cost_qual_eval_node(&cost, (Node *) phinfo->ph_var->phexpr,
+ root);
+ joinrel->reltarget->cost.startup += cost.startup;
+ joinrel->reltarget->cost.per_tuple += cost.per_tuple;
+ }
+
+ /* Adjust joinrel's direct_lateral_relids as needed */
+ joinrel->direct_lateral_relids =
+ bms_add_members(joinrel->direct_lateral_relids,
+ phinfo->ph_lateral);
}
}
}
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