* allpaths.c
* Routines to find possible search paths for processing a query
*
- * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.166 2007/11/15 21:14:35 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.187 2009/10/12 18:10:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
+#include <math.h>
+
+#include "nodes/nodeFuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
+#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "parser/parse_clause.h"
-#include "parser/parse_expr.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
RangeTblEntry *rte);
static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
+static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
+ RangeTblEntry *rte);
+static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
+ RangeTblEntry *rte);
static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
bool *differentTypes);
}
else if (rel->rtekind == RTE_FUNCTION)
{
- /* RangeFunction --- generate a separate plan for it */
+ /* RangeFunction --- generate a suitable path for it */
set_function_pathlist(root, rel, rte);
}
else if (rel->rtekind == RTE_VALUES)
{
- /* Values list --- generate a separate plan for it */
+ /* Values list --- generate a suitable path for it */
set_values_pathlist(root, rel, rte);
}
+ else if (rel->rtekind == RTE_CTE)
+ {
+ /* CTE reference --- generate a suitable path for it */
+ if (rte->self_reference)
+ set_worktable_pathlist(root, rel, rte);
+ else
+ set_cte_pathlist(root, rel, rte);
+ }
else
{
/* Plain relation */
* set_append_rel_pathlist().
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- relation_excluded_by_constraints(rel, rte))
+ relation_excluded_by_constraints(root, rel, rte))
{
set_dummy_rel_pathlist(rel);
return;
}
+ /*
+ * Test any partial indexes of rel for applicability. We must do this
+ * first since partial unique indexes can affect size estimates.
+ */
+ check_partial_indexes(root, rel);
+
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
- /* Test any partial indexes of rel for applicability */
- check_partial_indexes(root, rel);
-
/*
* Check to see if we can extract any restriction conditions from join
* quals that are OR-of-AND structures. If so, add them to the rel's
- * restriction list, and recompute the size estimates.
+ * restriction list, and redo the above steps.
*/
if (create_or_index_quals(root, rel))
+ {
+ check_partial_indexes(root, rel);
set_baserel_size_estimates(root, rel);
+ }
/*
* Generate paths and add them to the rel's pathlist.
{
int parentRTindex = rti;
List *subpaths = NIL;
+ double parent_rows;
+ double parent_size;
+ double *parent_attrsizes;
+ int nattrs;
ListCell *l;
/*
- * XXX for now, can't handle inherited expansion of FOR UPDATE/SHARE; can
- * we do better? (This will take some redesign because the executor
- * currently supposes that every rowMark relation is involved in every row
- * returned by the query.)
- */
- if (get_rowmark(root->parse, parentRTindex))
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("SELECT FOR UPDATE/SHARE is not supported for inheritance queries")));
-
- /*
- * Initialize to compute size estimates for whole append relation
+ * Initialize to compute size estimates for whole append relation.
+ *
+ * We handle width estimates by weighting the widths of different child
+ * rels proportionally to their number of rows. This is sensible because
+ * the use of width estimates is mainly to compute the total relation
+ * "footprint" if we have to sort or hash it. To do this, we sum the
+ * total equivalent size (in "double" arithmetic) and then divide by the
+ * total rowcount estimate. This is done separately for the total rel
+ * width and each attribute.
+ *
+ * Note: if you consider changing this logic, beware that child rels could
+ * have zero rows and/or width, if they were excluded by constraints.
*/
- rel->rows = 0;
- rel->width = 0;
+ parent_rows = 0;
+ parent_size = 0;
+ nattrs = rel->max_attr - rel->min_attr + 1;
+ parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
/*
* Generate access paths for each member relation, and pick the cheapest
int childRTindex;
RangeTblEntry *childRTE;
RelOptInfo *childrel;
+ List *childquals;
+ Node *childqual;
Path *childpath;
ListCell *parentvars;
ListCell *childvars;
* baserestrictinfo quals are needed before we can check for
* constraint exclusion; so do that first and then check to see if we
* can disregard this child.
+ *
+ * As of 8.4, the child rel's targetlist might contain non-Var
+ * expressions, which means that substitution into the quals
+ * could produce opportunities for const-simplification, and perhaps
+ * even pseudoconstant quals. To deal with this, we strip the
+ * RestrictInfo nodes, do the substitution, do const-simplification,
+ * and then reconstitute the RestrictInfo layer.
*/
- childrel->baserestrictinfo = (List *)
- adjust_appendrel_attrs((Node *) rel->baserestrictinfo,
- appinfo);
+ childquals = get_all_actual_clauses(rel->baserestrictinfo);
+ childquals = (List *) adjust_appendrel_attrs((Node *) childquals,
+ appinfo);
+ childqual = eval_const_expressions(root, (Node *)
+ make_ands_explicit(childquals));
+ if (childqual && IsA(childqual, Const) &&
+ (((Const *) childqual)->constisnull ||
+ !DatumGetBool(((Const *) childqual)->constvalue)))
+ {
+ /*
+ * Restriction reduces to constant FALSE or constant NULL after
+ * substitution, so this child need not be scanned.
+ */
+ set_dummy_rel_pathlist(childrel);
+ continue;
+ }
+ childquals = make_ands_implicit((Expr *) childqual);
+ childquals = make_restrictinfos_from_actual_clauses(root,
+ childquals);
+ childrel->baserestrictinfo = childquals;
- if (relation_excluded_by_constraints(childrel, childRTE))
+ if (relation_excluded_by_constraints(root, childrel, childRTE))
{
/*
* This child need not be scanned, so we can omit it from the
}
/*
- * Copy the parent's attr_needed data as well, with appropriate
- * adjustment of relids and attribute numbers.
+ * Note: we could compute appropriate attr_needed data for the child's
+ * variables, by transforming the parent's attr_needed through the
+ * translated_vars mapping. However, currently there's no need
+ * because attr_needed is only examined for base relations not
+ * otherrels. So we just leave the child's attr_needed empty.
*/
- pfree(childrel->attr_needed);
- childrel->attr_needed =
- adjust_appendrel_attr_needed(rel, appinfo,
- childrel->min_attr,
- childrel->max_attr);
/*
* Compute the child's access paths, and add the cheapest one to the
subpaths = lappend(subpaths, childpath);
/*
- * Propagate size information from the child back to the parent. For
- * simplicity, we use the largest widths from any child as the parent
- * estimates. (If you want to change this, beware of child
- * attr_widths[] entries that haven't been set and are still 0.)
+ * Accumulate size information from each child.
*/
- rel->rows += childrel->rows;
- if (childrel->width > rel->width)
- rel->width = childrel->width;
-
- forboth(parentvars, rel->reltargetlist,
- childvars, childrel->reltargetlist)
+ if (childrel->rows > 0)
{
- Var *parentvar = (Var *) lfirst(parentvars);
- Var *childvar = (Var *) lfirst(childvars);
+ parent_rows += childrel->rows;
+ parent_size += childrel->width * childrel->rows;
- if (IsA(parentvar, Var) &&
- IsA(childvar, Var))
+ forboth(parentvars, rel->reltargetlist,
+ childvars, childrel->reltargetlist)
{
- int pndx = parentvar->varattno - rel->min_attr;
- int cndx = childvar->varattno - childrel->min_attr;
-
- if (childrel->attr_widths[cndx] > rel->attr_widths[pndx])
- rel->attr_widths[pndx] = childrel->attr_widths[cndx];
+ Var *parentvar = (Var *) lfirst(parentvars);
+ Var *childvar = (Var *) lfirst(childvars);
+
+ /*
+ * Accumulate per-column estimates too. Whole-row Vars and
+ * PlaceHolderVars can be ignored here.
+ */
+ if (IsA(parentvar, Var) &&
+ IsA(childvar, Var))
+ {
+ int pndx = parentvar->varattno - rel->min_attr;
+ int cndx = childvar->varattno - childrel->min_attr;
+
+ parent_attrsizes[pndx] += childrel->attr_widths[cndx] * childrel->rows;
+ }
}
}
}
+ /*
+ * Save the finished size estimates.
+ */
+ rel->rows = parent_rows;
+ if (parent_rows > 0)
+ {
+ int i;
+
+ rel->width = rint(parent_size / parent_rows);
+ for (i = 0; i < nattrs; i++)
+ rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
+ }
+ else
+ rel->width = 0; /* attr_widths should be zero already */
+
/*
* Set "raw tuples" count equal to "rows" for the appendrel; needed
* because some places assume rel->tuples is valid for any baserel.
*/
- rel->tuples = rel->rows;
+ rel->tuples = parent_rows;
+
+ pfree(parent_attrsizes);
/*
* Finally, build Append path and install it as the only access path for
* Build a dummy path for a relation that's been excluded by constraints
*
* Rather than inventing a special "dummy" path type, we represent this as an
- * AppendPath with no members.
+ * AppendPath with no members (see also IS_DUMMY_PATH macro).
*/
static void
set_dummy_rel_pathlist(RelOptInfo *rel)
PlannerInfo *subroot;
List *pathkeys;
+ /*
+ * Must copy the Query so that planning doesn't mess up the RTE contents
+ * (really really need to fix the planner to not scribble on its input,
+ * someday).
+ */
+ subquery = copyObject(subquery);
+
/* We need a workspace for keeping track of set-op type coercions */
differentTypes = (bool *)
palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));
/* Generate the plan for the subquery */
rel->subplan = subquery_planner(root->glob, subquery,
- root->query_level + 1,
- tuple_fraction,
+ root,
+ false, tuple_fraction,
&subroot);
rel->subrtable = subroot->parse->rtable;
+ rel->subrowmark = subroot->parse->rowMarks;
/* Copy number of output rows from subplan */
rel->tuples = rel->subplan->plan_rows;
set_cheapest(rel);
}
+/*
+ * set_cte_pathlist
+ * Build the (single) access path for a non-self-reference CTE RTE
+ */
+static void
+set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+ Plan *cteplan;
+ PlannerInfo *cteroot;
+ Index levelsup;
+ int ndx;
+ ListCell *lc;
+ int plan_id;
+
+ /*
+ * Find the referenced CTE, and locate the plan previously made for it.
+ */
+ levelsup = rte->ctelevelsup;
+ cteroot = root;
+ while (levelsup-- > 0)
+ {
+ cteroot = cteroot->parent_root;
+ if (!cteroot) /* shouldn't happen */
+ elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
+ }
+
+ /*
+ * Note: cte_plan_ids can be shorter than cteList, if we are still working
+ * on planning the CTEs (ie, this is a side-reference from another CTE).
+ * So we mustn't use forboth here.
+ */
+ ndx = 0;
+ foreach(lc, cteroot->parse->cteList)
+ {
+ CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
+
+ if (strcmp(cte->ctename, rte->ctename) == 0)
+ break;
+ ndx++;
+ }
+ if (lc == NULL) /* shouldn't happen */
+ elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
+ if (ndx >= list_length(cteroot->cte_plan_ids))
+ elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
+ plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
+ Assert(plan_id > 0);
+ cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
+
+ /* Mark rel with estimated output rows, width, etc */
+ set_cte_size_estimates(root, rel, cteplan);
+
+ /* Generate appropriate path */
+ add_path(rel, create_ctescan_path(root, rel));
+
+ /* Select cheapest path (pretty easy in this case...) */
+ set_cheapest(rel);
+}
+
+/*
+ * set_worktable_pathlist
+ * Build the (single) access path for a self-reference CTE RTE
+ */
+static void
+set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+ Plan *cteplan;
+ PlannerInfo *cteroot;
+ Index levelsup;
+
+ /*
+ * We need to find the non-recursive term's plan, which is in the plan
+ * level that's processing the recursive UNION, which is one level *below*
+ * where the CTE comes from.
+ */
+ levelsup = rte->ctelevelsup;
+ if (levelsup == 0) /* shouldn't happen */
+ elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
+ levelsup--;
+ cteroot = root;
+ while (levelsup-- > 0)
+ {
+ cteroot = cteroot->parent_root;
+ if (!cteroot) /* shouldn't happen */
+ elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
+ }
+ cteplan = cteroot->non_recursive_plan;
+ if (!cteplan) /* shouldn't happen */
+ elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
+
+ /* Mark rel with estimated output rows, width, etc */
+ set_cte_size_estimates(root, rel, cteplan);
+
+ /* Generate appropriate path */
+ add_path(rel, create_worktablescan_path(root, rel));
+
+ /* Select cheapest path (pretty easy in this case...) */
+ set_cheapest(rel);
+}
+
/*
* make_rel_from_joinlist
* Build access paths using a "joinlist" to guide the join path search.
/*
* Consider the different orders in which we could join the rels,
* using a plugin, GEQO, or the regular join search code.
+ *
+ * We put the initial_rels list into a PlannerInfo field because
+ * has_legal_joinclause() needs to look at it (ugly :-().
*/
+ root->initial_rels = initial_rels;
+
if (join_search_hook)
return (*join_search_hook) (root, levels_needed, initial_rels);
else if (enable_geqo && levels_needed >= geqo_threshold)
* 1. If the subquery has a LIMIT clause, we must not push down any quals,
* since that could change the set of rows returned.
*
- * 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
- * quals into it, because that would change the results.
+ * 2. If the subquery contains any window functions, we can't push quals
+ * into it, because that could change the results.
+ *
+ * 3. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
+ * quals into it, because that could change the results.
*
- * 3. For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
+ * 4. For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
* push quals into each component query, but the quals can only reference
* subquery columns that suffer no type coercions in the set operation.
* Otherwise there are possible semantic gotchas. So, we check the
if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
return false;
+ /* Check point 2 */
+ if (subquery->hasWindowFuncs)
+ return false;
+
/* Are we at top level, or looking at a setop component? */
if (subquery == topquery)
{
*
* 4. If the subquery uses DISTINCT ON, we must not push down any quals that
* refer to non-DISTINCT output columns, because that could change the set
- * of rows returned. This condition is vacuous for DISTINCT, because then
- * there are no non-DISTINCT output columns, but unfortunately it's fairly
- * expensive to tell the difference between DISTINCT and DISTINCT ON in the
- * parsetree representation. It's cheaper to just make sure all the Vars
- * in the qual refer to DISTINCT columns.
+ * of rows returned. (This condition is vacuous for DISTINCT, because then
+ * there are no non-DISTINCT output columns, so we needn't check. But note
+ * we are assuming that the qual can't distinguish values that the DISTINCT
+ * operator sees as equal. This is a bit shaky but we have no way to test
+ * for the case, and it's unlikely enough that we shouldn't refuse the
+ * optimization just because it could theoretically happen.)
*
* 5. We must not push down any quals that refer to subselect outputs that
* return sets, else we'd introduce functions-returning-sets into the
if (contain_subplans(qual))
return false;
+ /*
+ * It would be unsafe to push down window function calls, but at least for
+ * the moment we could never see any in a qual anyhow.
+ */
+ Assert(!contain_window_function(qual));
+
/*
* Examine all Vars used in clause; since it's a restriction clause, all
* such Vars must refer to subselect output columns.
*/
- vars = pull_var_clause(qual, false);
+ vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
foreach(vl, vars)
{
Var *var = (Var *) lfirst(vl);
TargetEntry *tle;
+ /*
+ * XXX Punt if we find any PlaceHolderVars in the restriction clause.
+ * It's not clear whether a PHV could safely be pushed down, and even
+ * less clear whether such a situation could arise in any cases of
+ * practical interest anyway. So for the moment, just refuse to push
+ * down.
+ */
+ if (!IsA(var, Var))
+ {
+ safe = false;
+ break;
+ }
+
Assert(var->varno == rti);
/* Check point 2 */
Assert(tle != NULL);
Assert(!tle->resjunk);
- /* If subquery uses DISTINCT or DISTINCT ON, check point 4 */
- if (subquery->distinctClause != NIL &&
+ /* If subquery uses DISTINCT ON, check point 4 */
+ if (subquery->hasDistinctOn &&
!targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
{
/* non-DISTINCT column, so fail */
*/
qual = ResolveNew(qual, rti, 0, rte,
subquery->targetList,
- CMD_SELECT, 0);
+ CMD_SELECT, 0,
+ &subquery->hasSubLinks);
/*
* Now attach the qual to the proper place: normally WHERE, but if the
ptype = "Unique";
subpath = ((UniquePath *) path)->subpath;
break;
+ case T_NoOpPath:
+ ptype = "NoOp";
+ subpath = ((NoOpPath *) path)->subpath;
+ break;
case T_NestPath:
ptype = "NestLoop";
join = true;
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