* planner.c
* The query optimizer external interface.
*
- * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.88 2000/08/21 20:55:29 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.172 2004/06/11 01:08:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
+#include <limits.h>
+
+#include "catalog/pg_operator.h"
#include "catalog/pg_type.h"
+#include "executor/executor.h"
+#include "miscadmin.h"
#include "nodes/makefuncs.h"
+#ifdef OPTIMIZER_DEBUG
+#include "nodes/print.h"
+#endif
#include "optimizer/clauses.h"
+#include "optimizer/cost.h"
+#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
+#include "parser/analyze.h"
+#include "parser/parsetree.h"
#include "parser/parse_expr.h"
-#include "utils/lsyscache.h"
+#include "parser/parse_oper.h"
+#include "utils/selfuncs.h"
+#include "utils/syscache.h"
+
+
+ParamListInfo PlannerBoundParamList = NULL; /* current boundParams */
+
+/* Expression kind codes for preprocess_expression */
+#define EXPRKIND_QUAL 0
+#define EXPRKIND_TARGET 1
+#define EXPRKIND_RTFUNC 2
+#define EXPRKIND_LIMIT 3
+#define EXPRKIND_ININFO 4
+
+static Node *preprocess_expression(Query *parse, Node *expr, int kind);
+static void preprocess_qual_conditions(Query *parse, Node *jtnode);
+static Plan *inheritance_planner(Query *parse, List *inheritlist);
+static Plan *grouping_planner(Query *parse, double tuple_fraction);
+static bool hash_safe_grouping(Query *parse);
static List *make_subplanTargetList(Query *parse, List *tlist,
- AttrNumber **groupColIdx);
-static Plan *make_groupplan(List *group_tlist, bool tuplePerGroup,
- List *groupClause, AttrNumber *grpColIdx,
- bool is_presorted, Plan *subplan);
-static Plan *make_sortplan(List *tlist, Plan *plannode, List *sortcls);
+ AttrNumber **groupColIdx, bool *need_tlist_eval);
+static void locate_grouping_columns(Query *parse,
+ List *tlist,
+ List *sub_tlist,
+ AttrNumber *groupColIdx);
+static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
+
/*****************************************************************************
*
*
*****************************************************************************/
Plan *
-planner(Query *parse)
+planner(Query *parse, bool isCursor, int cursorOptions,
+ ParamListInfo boundParams)
{
+ double tuple_fraction;
Plan *result_plan;
Index save_PlannerQueryLevel;
- List *save_PlannerInitPlan;
- List *save_PlannerParamVar;
- int save_PlannerPlanId;
+ List *save_PlannerParamList;
+ ParamListInfo save_PlannerBoundParamList;
/*
* The planner can be called recursively (an example is when
- * eval_const_expressions tries to simplify an SQL function).
- * So, global state variables must be saved and restored.
+ * eval_const_expressions tries to pre-evaluate an SQL function). So,
+ * these global state variables must be saved and restored.
+ *
+ * Query level and the param list cannot be moved into the Query structure
+ * since their whole purpose is communication across multiple sub-Queries.
+ * Also, boundParams is explicitly info from outside the Query, and so
+ * is likewise better handled as a global variable.
*
- * (Perhaps these should be moved into the Query structure instead?)
+ * Note we do NOT save and restore PlannerPlanId: it exists to assign
+ * unique IDs to SubPlan nodes, and we want those IDs to be unique for
+ * the life of a backend. Also, PlannerInitPlan is saved/restored in
+ * subquery_planner, not here.
*/
save_PlannerQueryLevel = PlannerQueryLevel;
- save_PlannerInitPlan = PlannerInitPlan;
- save_PlannerParamVar = PlannerParamVar;
- save_PlannerPlanId = PlannerPlanId;
+ save_PlannerParamList = PlannerParamList;
+ save_PlannerBoundParamList = PlannerBoundParamList;
- /* Initialize state for subselects */
- PlannerQueryLevel = 1;
- PlannerInitPlan = NULL;
- PlannerParamVar = NULL;
- PlannerPlanId = 0;
+ /* Initialize state for handling outer-level references and params */
+ PlannerQueryLevel = 0; /* will be 1 in top-level subquery_planner */
+ PlannerParamList = NIL;
+ PlannerBoundParamList = boundParams;
- /* this should go away sometime soon */
- transformKeySetQuery(parse);
+ /* Determine what fraction of the plan is likely to be scanned */
+ if (isCursor)
+ {
+ /*
+ * We have no real idea how many tuples the user will ultimately
+ * FETCH from a cursor, but it seems a good bet that he doesn't
+ * want 'em all. Optimize for 10% retrieval (you gotta better
+ * number? Should this be a SETtable parameter?)
+ */
+ tuple_fraction = 0.10;
+ }
+ else
+ {
+ /* Default assumption is we need all the tuples */
+ tuple_fraction = 0.0;
+ }
- /* primary planning entry point (may recurse for subplans) */
- result_plan = subquery_planner(parse, -1.0 /* default case */ );
+ /* primary planning entry point (may recurse for subqueries) */
+ result_plan = subquery_planner(parse, tuple_fraction);
- Assert(PlannerQueryLevel == 1);
+ Assert(PlannerQueryLevel == 0);
- /* if top-level query had subqueries, do housekeeping for them */
- if (PlannerPlanId > 0)
+ /*
+ * If creating a plan for a scrollable cursor, make sure it can run
+ * backwards on demand. Add a Material node at the top at need.
+ */
+ if (isCursor && (cursorOptions & CURSOR_OPT_SCROLL))
{
- (void) SS_finalize_plan(result_plan);
- result_plan->initPlan = PlannerInitPlan;
+ if (!ExecSupportsBackwardScan(result_plan))
+ result_plan = materialize_finished_plan(result_plan);
}
/* executor wants to know total number of Params used overall */
- result_plan->nParamExec = length(PlannerParamVar);
+ result_plan->nParamExec = list_length(PlannerParamList);
/* final cleanup of the plan */
- set_plan_references(result_plan);
+ set_plan_references(result_plan, parse->rtable);
/* restore state for outer planner, if any */
PlannerQueryLevel = save_PlannerQueryLevel;
- PlannerInitPlan = save_PlannerInitPlan;
- PlannerParamVar = save_PlannerParamVar;
- PlannerPlanId = save_PlannerPlanId;
+ PlannerParamList = save_PlannerParamList;
+ PlannerBoundParamList = save_PlannerBoundParamList;
return result_plan;
}
*
* parse is the querytree produced by the parser & rewriter.
* tuple_fraction is the fraction of tuples we expect will be retrieved.
- * tuple_fraction is interpreted as explained for union_planner, below.
+ * tuple_fraction is interpreted as explained for grouping_planner, below.
*
* Basically, this routine does the stuff that should only be done once
- * per Query object. It then calls union_planner, which may be called
- * recursively on the same Query node in order to handle UNIONs and/or
- * inheritance. subquery_planner is called recursively from subselect.c
- * to handle sub-Query nodes found within the query's expressions.
+ * per Query object. It then calls grouping_planner. At one time,
+ * grouping_planner could be invoked recursively on the same Query object;
+ * that's not currently true, but we keep the separation between the two
+ * routines anyway, in case we need it again someday.
*
- * prepunion.c uses an unholy combination of calling union_planner when
- * recursing on the primary Query node, or subquery_planner when recursing
- * on a UNION'd Query node that hasn't previously been seen by
- * subquery_planner. That whole chunk of code needs rewritten from scratch.
+ * subquery_planner will be called recursively to handle sub-Query nodes
+ * found within the query's expressions and rangetable.
*
* Returns a query plan.
*--------------------
Plan *
subquery_planner(Query *parse, double tuple_fraction)
{
+ List *saved_initplan = PlannerInitPlan;
+ int saved_planid = PlannerPlanId;
+ bool hasOuterJoins;
+ Plan *plan;
+ List *newHaving;
+ List *lst;
+ ListCell *l;
+
+ /* Set up for a new level of subquery */
+ PlannerQueryLevel++;
+ PlannerInitPlan = NIL;
+
+ /*
+ * Look for IN clauses at the top level of WHERE, and transform them
+ * into joins. Note that this step only handles IN clauses originally
+ * at top level of WHERE; if we pull up any subqueries in the next
+ * step, their INs are processed just before pulling them up.
+ */
+ parse->in_info_list = NIL;
+ if (parse->hasSubLinks)
+ parse->jointree->quals = pull_up_IN_clauses(parse,
+ parse->jointree->quals);
+
+ /*
+ * Check to see if any subqueries in the rangetable can be merged into
+ * this query.
+ */
+ parse->jointree = (FromExpr *)
+ pull_up_subqueries(parse, (Node *) parse->jointree, false);
+
+ /*
+ * Detect whether any rangetable entries are RTE_JOIN kind; if not, we
+ * can avoid the expense of doing flatten_join_alias_vars(). Also
+ * check for outer joins --- if none, we can skip
+ * reduce_outer_joins(). This must be done after we have done
+ * pull_up_subqueries, of course.
+ */
+ parse->hasJoinRTEs = false;
+ hasOuterJoins = false;
+ foreach(l, parse->rtable)
+ {
+ RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
+
+ if (rte->rtekind == RTE_JOIN)
+ {
+ parse->hasJoinRTEs = true;
+ if (IS_OUTER_JOIN(rte->jointype))
+ {
+ hasOuterJoins = true;
+ /* Can quit scanning once we find an outer join */
+ break;
+ }
+ }
+ }
+
+ /*
+ * Do expression preprocessing on targetlist and quals.
+ */
+ parse->targetList = (List *)
+ preprocess_expression(parse, (Node *) parse->targetList,
+ EXPRKIND_TARGET);
+
+ preprocess_qual_conditions(parse, (Node *) parse->jointree);
+
+ parse->havingQual = preprocess_expression(parse, parse->havingQual,
+ EXPRKIND_QUAL);
+
+ parse->limitOffset = preprocess_expression(parse, parse->limitOffset,
+ EXPRKIND_LIMIT);
+ parse->limitCount = preprocess_expression(parse, parse->limitCount,
+ EXPRKIND_LIMIT);
+
+ parse->in_info_list = (List *)
+ preprocess_expression(parse, (Node *) parse->in_info_list,
+ EXPRKIND_ININFO);
+
+ /* Also need to preprocess expressions for function RTEs */
+ foreach(l, parse->rtable)
+ {
+ RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
+
+ if (rte->rtekind == RTE_FUNCTION)
+ rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
+ EXPRKIND_RTFUNC);
+ }
+
/*
* A HAVING clause without aggregates is equivalent to a WHERE clause
- * (except it can only refer to grouped fields). If there are no aggs
- * anywhere in the query, then we don't want to create an Agg plan
- * node, so merge the HAVING condition into WHERE. (We used to
- * consider this an error condition, but it seems to be legal SQL.)
+ * (except it can only refer to grouped fields). Transfer any
+ * agg-free clauses of the HAVING qual into WHERE. This may seem like
+ * wasting cycles to cater to stupidly-written queries, but there are
+ * other reasons for doing it. Firstly, if the query contains no aggs
+ * at all, then we aren't going to generate an Agg plan node, and so
+ * there'll be no place to execute HAVING conditions; without this
+ * transfer, we'd lose the HAVING condition entirely, which is wrong.
+ * Secondly, when we push down a qual condition into a sub-query, it's
+ * easiest to push the qual into HAVING always, in case it contains
+ * aggs, and then let this code sort it out.
+ *
+ * Note that both havingQual and parse->jointree->quals are in
+ * implicitly-ANDed-list form at this point, even though they are
+ * declared as Node *.
*/
- if (parse->havingQual != NULL && !parse->hasAggs)
+ newHaving = NIL;
+ foreach(l, (List *) parse->havingQual)
{
- if (parse->qual == NULL)
- parse->qual = parse->havingQual;
+ Node *havingclause = (Node *) lfirst(l);
+
+ if (contain_agg_clause(havingclause))
+ newHaving = lappend(newHaving, havingclause);
else
- parse->qual = (Node *) make_andclause(lappend(lcons(parse->qual,
- NIL),
- parse->havingQual));
- parse->havingQual = NULL;
+ parse->jointree->quals = (Node *)
+ lappend((List *) parse->jointree->quals, havingclause);
}
+ parse->havingQual = (Node *) newHaving;
/*
- * Simplify constant expressions in targetlist and quals.
- *
- * Note that at this point the qual has not yet been converted to
- * implicit-AND form, so we can apply eval_const_expressions directly.
- * Also note that we need to do this before SS_process_sublinks,
- * because that routine inserts bogus "Const" nodes.
+ * If we have any outer joins, try to reduce them to plain inner
+ * joins. This step is most easily done after we've done expression
+ * preprocessing.
*/
- parse->targetList = (List *)
- eval_const_expressions((Node *) parse->targetList);
- parse->qual = eval_const_expressions(parse->qual);
- parse->havingQual = eval_const_expressions(parse->havingQual);
+ if (hasOuterJoins)
+ reduce_outer_joins(parse);
+
+ /*
+ * See if we can simplify the jointree; opportunities for this may
+ * come from having pulled up subqueries, or from flattening explicit
+ * JOIN syntax. We must do this after flattening JOIN alias
+ * variables, since eliminating explicit JOIN nodes from the jointree
+ * will cause get_relids_for_join() to fail. But it should happen
+ * after reduce_outer_joins, anyway.
+ */
+ parse->jointree = (FromExpr *)
+ simplify_jointree(parse, (Node *) parse->jointree);
+
+ /*
+ * Do the main planning. If we have an inherited target relation,
+ * that needs special processing, else go straight to
+ * grouping_planner.
+ */
+ if (parse->resultRelation &&
+ (lst = expand_inherited_rtentry(parse, parse->resultRelation,
+ false)) != NIL)
+ plan = inheritance_planner(parse, lst);
+ else
+ plan = grouping_planner(parse, tuple_fraction);
/*
- * Canonicalize the qual, and convert it to implicit-AND format.
+ * If any subplans were generated, or if we're inside a subplan, build
+ * initPlan list and extParam/allParam sets for plan nodes.
+ */
+ if (PlannerPlanId != saved_planid || PlannerQueryLevel > 1)
+ {
+ Cost initplan_cost = 0;
+
+ /* Prepare extParam/allParam sets for all nodes in tree */
+ SS_finalize_plan(plan, parse->rtable);
+
+ /*
+ * SS_finalize_plan doesn't handle initPlans, so we have to
+ * manually attach them to the topmost plan node, and add their
+ * extParams to the topmost node's, too.
+ *
+ * We also add the total_cost of each initPlan to the startup cost of
+ * the top node. This is a conservative overestimate, since in
+ * fact each initPlan might be executed later than plan startup,
+ * or even not at all.
+ */
+ plan->initPlan = PlannerInitPlan;
+
+ foreach(l, plan->initPlan)
+ {
+ SubPlan *initplan = (SubPlan *) lfirst(l);
+
+ plan->extParam = bms_add_members(plan->extParam,
+ initplan->plan->extParam);
+ /* allParam must include all members of extParam */
+ plan->allParam = bms_add_members(plan->allParam,
+ plan->extParam);
+ initplan_cost += initplan->plan->total_cost;
+ }
+
+ plan->startup_cost += initplan_cost;
+ plan->total_cost += initplan_cost;
+ }
+
+ /* Return to outer subquery context */
+ PlannerQueryLevel--;
+ PlannerInitPlan = saved_initplan;
+ /* we do NOT restore PlannerPlanId; that's not an oversight! */
+
+ return plan;
+}
+
+/*
+ * preprocess_expression
+ * Do subquery_planner's preprocessing work for an expression,
+ * which can be a targetlist, a WHERE clause (including JOIN/ON
+ * conditions), or a HAVING clause.
+ */
+static Node *
+preprocess_expression(Query *parse, Node *expr, int kind)
+{
+ /*
+ * If the query has any join RTEs, replace join alias variables with
+ * base-relation variables. We must do this before sublink processing,
+ * else sublinks expanded out from join aliases wouldn't get
+ * processed.
+ */
+ if (parse->hasJoinRTEs)
+ expr = flatten_join_alias_vars(parse, expr);
+
+ /*
+ * If it's a qual or havingQual, canonicalize it. It seems most useful
+ * to do this before applying eval_const_expressions, since the latter
+ * can optimize flattened AND/ORs better than unflattened ones.
*
- * XXX Is there any value in re-applying eval_const_expressions after
- * canonicalize_qual?
+ * Note: all processing of a qual expression after this point must be
+ * careful to maintain AND/OR flatness --- that is, do not generate a
+ * tree with AND directly under AND, nor OR directly under OR.
*/
- parse->qual = (Node *) canonicalize_qual((Expr *) parse->qual, true);
+ if (kind == EXPRKIND_QUAL)
+ {
+ expr = (Node *) canonicalize_qual((Expr *) expr);
+
#ifdef OPTIMIZER_DEBUG
- printf("After canonicalize_qual()\n");
- pprint(parse->qual);
+ printf("After canonicalize_qual()\n");
+ pprint(expr);
#endif
+ }
/*
- * Ditto for the havingQual
+ * Simplify constant expressions.
*/
- parse->havingQual = (Node *) canonicalize_qual((Expr *) parse->havingQual,
- true);
+ expr = eval_const_expressions(expr);
/* Expand SubLinks to SubPlans */
if (parse->hasSubLinks)
- {
- parse->targetList = (List *)
- SS_process_sublinks((Node *) parse->targetList);
- parse->qual = SS_process_sublinks(parse->qual);
- parse->havingQual = SS_process_sublinks(parse->havingQual);
-
- if (parse->groupClause != NIL)
- {
+ expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
- /*
- * Check for ungrouped variables passed to subplans. Note we
- * do NOT do this for subplans in WHERE; it's legal there
- * because WHERE is evaluated pre-GROUP.
- *
- * An interesting fine point: if we reassigned a HAVING qual into
- * WHERE above, then we will accept references to ungrouped
- * vars from subplans in the HAVING qual. This is not
- * entirely consistent, but it doesn't seem particularly
- * harmful...
- */
- check_subplans_for_ungrouped_vars((Node *) parse->targetList,
- parse);
- check_subplans_for_ungrouped_vars(parse->havingQual, parse);
- }
- }
+ /*
+ * XXX do not insert anything here unless you have grokked the
+ * comments in SS_replace_correlation_vars ...
+ */
/* Replace uplevel vars with Param nodes */
if (PlannerQueryLevel > 1)
+ expr = SS_replace_correlation_vars(expr);
+
+ /*
+ * If it's a qual or havingQual, convert it to implicit-AND format.
+ * (We don't want to do this before eval_const_expressions, since the
+ * latter would be unable to simplify a top-level AND correctly. Also,
+ * SS_process_sublinks expects explicit-AND format.)
+ */
+ if (kind == EXPRKIND_QUAL)
+ expr = (Node *) make_ands_implicit((Expr *) expr);
+
+ return expr;
+}
+
+/*
+ * preprocess_qual_conditions
+ * Recursively scan the query's jointree and do subquery_planner's
+ * preprocessing work on each qual condition found therein.
+ */
+static void
+preprocess_qual_conditions(Query *parse, Node *jtnode)
+{
+ if (jtnode == NULL)
+ return;
+ if (IsA(jtnode, RangeTblRef))
{
- parse->targetList = (List *)
- SS_replace_correlation_vars((Node *) parse->targetList);
- parse->qual = SS_replace_correlation_vars(parse->qual);
- parse->havingQual = SS_replace_correlation_vars(parse->havingQual);
+ /* nothing to do here */
}
+ else if (IsA(jtnode, FromExpr))
+ {
+ FromExpr *f = (FromExpr *) jtnode;
+ ListCell *l;
+
+ foreach(l, f->fromlist)
+ preprocess_qual_conditions(parse, lfirst(l));
- /* Do the main planning (potentially recursive) */
+ f->quals = preprocess_expression(parse, f->quals, EXPRKIND_QUAL);
+ }
+ else if (IsA(jtnode, JoinExpr))
+ {
+ JoinExpr *j = (JoinExpr *) jtnode;
- return union_planner(parse, tuple_fraction);
+ preprocess_qual_conditions(parse, j->larg);
+ preprocess_qual_conditions(parse, j->rarg);
- /*
- * XXX should any more of union_planner's activity be moved here?
- *
- * That would take careful study of the interactions with prepunion.c,
- * but I suspect it would pay off in simplicity and avoidance of
- * wasted cycles.
- */
+ j->quals = preprocess_expression(parse, j->quals, EXPRKIND_QUAL);
+ }
+ else
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
}
+/*--------------------
+ * inheritance_planner
+ * Generate a plan in the case where the result relation is an
+ * inheritance set.
+ *
+ * We have to handle this case differently from cases where a source
+ * relation is an inheritance set. Source inheritance is expanded at
+ * the bottom of the plan tree (see allpaths.c), but target inheritance
+ * has to be expanded at the top. The reason is that for UPDATE, each
+ * target relation needs a different targetlist matching its own column
+ * set. (This is not so critical for DELETE, but for simplicity we treat
+ * inherited DELETE the same way.) Fortunately, the UPDATE/DELETE target
+ * can never be the nullable side of an outer join, so it's OK to generate
+ * the plan this way.
+ *
+ * parse is the querytree produced by the parser & rewriter.
+ * inheritlist is an integer list of RT indexes for the result relation set.
+ *
+ * Returns a query plan.
+ *--------------------
+ */
+static Plan *
+inheritance_planner(Query *parse, List *inheritlist)
+{
+ int parentRTindex = parse->resultRelation;
+ Oid parentOID = getrelid(parentRTindex, parse->rtable);
+ int mainrtlength = list_length(parse->rtable);
+ List *subplans = NIL;
+ List *tlist = NIL;
+ ListCell *l;
+
+ foreach(l, inheritlist)
+ {
+ int childRTindex = lfirst_int(l);
+ Oid childOID = getrelid(childRTindex, parse->rtable);
+ int subrtlength;
+ Query *subquery;
+ Plan *subplan;
+
+ /* Generate modified query with this rel as target */
+ subquery = (Query *) adjust_inherited_attrs((Node *) parse,
+ parentRTindex, parentOID,
+ childRTindex, childOID);
+ /* Generate plan */
+ subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
+ subplans = lappend(subplans, subplan);
+
+ /*
+ * It's possible that additional RTEs got added to the rangetable
+ * due to expansion of inherited source tables (see allpaths.c).
+ * If so, we must copy 'em back to the main parse tree's rtable.
+ *
+ * XXX my goodness this is ugly. Really need to think about ways to
+ * rein in planner's habit of scribbling on its input.
+ */
+ subrtlength = list_length(subquery->rtable);
+ if (subrtlength > mainrtlength)
+ {
+ List *subrt;
+
+ subrt = list_copy_tail(subquery->rtable, mainrtlength);
+ parse->rtable = list_concat(parse->rtable, subrt);
+ mainrtlength = subrtlength;
+ }
+ /* Save preprocessed tlist from first rel for use in Append */
+ if (tlist == NIL)
+ tlist = subplan->targetlist;
+ }
+
+ /* Save the target-relations list for the executor, too */
+ parse->resultRelations = inheritlist;
+
+ /* Mark result as unordered (probably unnecessary) */
+ parse->query_pathkeys = NIL;
+
+ return (Plan *) make_append(subplans, true, tlist);
+}
/*--------------------
- * union_planner
- * Invokes the planner on union-type queries (both regular UNIONs and
- * appends produced by inheritance), recursing if necessary to get them
- * all, then processes normal plans.
+ * grouping_planner
+ * Perform planning steps related to grouping, aggregation, etc.
+ * This primarily means adding top-level processing to the basic
+ * query plan produced by query_planner.
*
* parse is the querytree produced by the parser & rewriter.
* tuple_fraction is the fraction of tuples we expect will be retrieved
*
* tuple_fraction is interpreted as follows:
- * < 0: determine fraction by inspection of query (normal case)
- * 0: expect all tuples to be retrieved
+ * 0: expect all tuples to be retrieved (normal case)
* 0 < tuple_fraction < 1: expect the given fraction of tuples available
* from the plan to be retrieved
* tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
* expected to be retrieved (ie, a LIMIT specification)
- * The normal case is to pass -1, but some callers pass values >= 0 to
- * override this routine's determination of the appropriate fraction.
*
- * Returns a query plan.
+ * Returns a query plan. Also, parse->query_pathkeys is returned as the
+ * actual output ordering of the plan (in pathkey format).
*--------------------
*/
-Plan *
-union_planner(Query *parse,
- double tuple_fraction)
+static Plan *
+grouping_planner(Query *parse, double tuple_fraction)
{
List *tlist = parse->targetList;
- List *rangetable = parse->rtable;
- Plan *result_plan = (Plan *) NULL;
- AttrNumber *groupColIdx = NULL;
- List *current_pathkeys = NIL;
- List *group_pathkeys;
+ Plan *result_plan;
+ List *current_pathkeys;
List *sort_pathkeys;
- Index rt_index;
- List *inheritors;
- if (parse->unionClause)
+ if (parse->setOperations)
{
- result_plan = plan_union_queries(parse);
- /* XXX do we need to do this? bjm 12/19/97 */
- tlist = preprocess_targetlist(tlist,
- parse->commandType,
- parse->resultRelation,
- parse->rtable);
-
- /*
- * We leave current_pathkeys NIL indicating we do not know sort
- * order. This is correct for the appended-together subplan
- * results, even if the subplans themselves produced sorted results.
- */
-
- /*
- * Calculate pathkeys that represent grouping/ordering
- * requirements
- */
- group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
- tlist);
- sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
- tlist);
- }
- else if (find_inheritable_rt_entry(rangetable,
- &rt_index, &inheritors))
- {
- List *sub_tlist;
+ List *set_sortclauses;
/*
- * Generate appropriate target list for subplan; may be different
- * from tlist if grouping or aggregation is needed.
+ * Construct the plan for set operations. The result will not
+ * need any work except perhaps a top-level sort and/or LIMIT.
*/
- sub_tlist = make_subplanTargetList(parse, tlist, &groupColIdx);
+ result_plan = plan_set_operations(parse,
+ &set_sortclauses);
/*
- * Recursively plan the subqueries needed for inheritance
+ * Calculate pathkeys representing the sort order (if any) of the
+ * set operation's result. We have to do this before overwriting
+ * the sort key information...
*/
- result_plan = plan_inherit_queries(parse, sub_tlist,
- rt_index, inheritors);
+ current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
+ result_plan->targetlist);
+ current_pathkeys = canonicalize_pathkeys(parse, current_pathkeys);
/*
- * Fix up outer target list. NOTE: unlike the case for
- * non-inherited query, we pass the unfixed tlist to subplans,
- * which do their own fixing. But we still want to fix the outer
- * target list afterwards. I *think* this is correct --- doing the
- * fix before recursing is definitely wrong, because
- * preprocess_targetlist() will do the wrong thing if invoked
- * twice on the same list. Maybe that is a bug? tgl 6/6/99
+ * We should not need to call preprocess_targetlist, since we must
+ * be in a SELECT query node. Instead, use the targetlist
+ * returned by plan_set_operations (since this tells whether it
+ * returned any resjunk columns!), and transfer any sort key
+ * information from the original tlist.
*/
- tlist = preprocess_targetlist(tlist,
- parse->commandType,
- parse->resultRelation,
- parse->rtable);
+ Assert(parse->commandType == CMD_SELECT);
- if (parse->rowMark != NULL)
- elog(ERROR, "SELECT FOR UPDATE is not supported for inherit queries");
+ tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
/*
- * We leave current_pathkeys NIL indicating we do not know sort
- * order of the Append-ed results.
+ * Can't handle FOR UPDATE here (parser should have checked
+ * already, but let's make sure).
*/
+ if (parse->rowMarks)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
/*
- * Calculate pathkeys that represent grouping/ordering
- * requirements
+ * Calculate pathkeys that represent result ordering requirements
*/
- group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
- tlist);
sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
tlist);
+ sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
}
else
{
+ /* No set operations, do regular planning */
List *sub_tlist;
+ List *group_pathkeys;
+ AttrNumber *groupColIdx = NULL;
+ bool need_tlist_eval = true;
+ QualCost tlist_cost;
+ double sub_tuple_fraction;
+ Path *cheapest_path;
+ Path *sorted_path;
+ double dNumGroups = 0;
+ long numGroups = 0;
+ int numAggs = 0;
+ int numGroupCols = list_length(parse->groupClause);
+ bool use_hashed_grouping = false;
/* Preprocess targetlist in case we are inside an INSERT/UPDATE. */
tlist = preprocess_targetlist(tlist,
parse->rtable);
/*
- * Add row-mark targets for UPDATE (should this be done in
- * preprocess_targetlist?)
+ * Add TID targets for rels selected FOR UPDATE (should this be
+ * done in preprocess_targetlist?). The executor uses the TID to
+ * know which rows to lock, much as for UPDATE or DELETE.
*/
- if (parse->rowMark != NULL)
+ if (parse->rowMarks)
{
- List *l;
+ ListCell *l;
+
+ /*
+ * We've got trouble if the FOR UPDATE appears inside
+ * grouping, since grouping renders a reference to individual
+ * tuple CTIDs invalid. This is also checked at parse time,
+ * but that's insufficient because of rule substitution, query
+ * pullup, etc.
+ */
+ CheckSelectForUpdate(parse);
+
+ /*
+ * Currently the executor only supports FOR UPDATE at top
+ * level
+ */
+ if (PlannerQueryLevel > 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("SELECT FOR UPDATE is not allowed in subqueries")));
- foreach(l, parse->rowMark)
+ foreach(l, parse->rowMarks)
{
- RowMark *rowmark = (RowMark *) lfirst(l);
- TargetEntry *ctid;
+ Index rti = lfirst_int(l);
+ char *resname;
Resdom *resdom;
Var *var;
- char *resname;
-
- if (!(rowmark->info & ROW_MARK_FOR_UPDATE))
- continue;
+ TargetEntry *ctid;
resname = (char *) palloc(32);
- sprintf(resname, "ctid%u", rowmark->rti);
- resdom = makeResdom(length(tlist) + 1,
+ snprintf(resname, 32, "ctid%u", rti);
+ resdom = makeResdom(list_length(tlist) + 1,
TIDOID,
-1,
resname,
true);
- var = makeVar(rowmark->rti, -1, TIDOID, -1, 0);
+ var = makeVar(rti,
+ SelfItemPointerAttributeNumber,
+ TIDOID,
+ -1,
+ 0);
- ctid = makeTargetEntry(resdom, (Node *) var);
+ ctid = makeTargetEntry(resdom, (Expr *) var);
tlist = lappend(tlist, ctid);
}
}
* Generate appropriate target list for subplan; may be different
* from tlist if grouping or aggregation is needed.
*/
- sub_tlist = make_subplanTargetList(parse, tlist, &groupColIdx);
+ sub_tlist = make_subplanTargetList(parse, tlist,
+ &groupColIdx, &need_tlist_eval);
/*
* Calculate pathkeys that represent grouping/ordering
sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
tlist);
+ /*
+ * Will need actual number of aggregates for estimating costs.
+ *
+ * Note: we do not attempt to detect duplicate aggregates here; a
+ * somewhat-overestimated count is okay for our present purposes.
+ *
+ * Note: think not that we can turn off hasAggs if we find no aggs.
+ * It is possible for constant-expression simplification to remove
+ * all explicit references to aggs, but we still have to follow the
+ * aggregate semantics (eg, producing only one output row).
+ */
+ if (parse->hasAggs)
+ numAggs = count_agg_clause((Node *) tlist) +
+ count_agg_clause(parse->havingQual);
+
/*
* Figure out whether we need a sorted result from query_planner.
*
parse->query_pathkeys = NIL;
/*
- * Figure out whether we expect to retrieve all the tuples that
- * the plan can generate, or to stop early due to a LIMIT or other
- * factors. If the caller passed a value >= 0, believe that
- * value, else do our own examination of the query context.
+ * Adjust tuple_fraction if we see that we are going to apply
+ * limiting/grouping/aggregation/etc. This is not overridable by
+ * the caller, since it reflects plan actions that this routine
+ * will certainly take, not assumptions about context.
*/
- if (tuple_fraction < 0.0)
+ if (parse->limitCount != NULL)
{
- /* Initial assumption is we need all the tuples */
- tuple_fraction = 0.0;
-
/*
- * Check for a LIMIT clause.
+ * A LIMIT clause limits the absolute number of tuples
+ * returned. However, if it's not a constant LIMIT then we
+ * have to punt; for lack of a better idea, assume 10% of the
+ * plan's result is wanted.
*/
- if (parse->limitCount != NULL)
+ double limit_fraction = 0.0;
+
+ if (IsA(parse->limitCount, Const))
{
- if (IsA(parse->limitCount, Const))
+ Const *limitc = (Const *) parse->limitCount;
+ int32 count = DatumGetInt32(limitc->constvalue);
+
+ /*
+ * A NULL-constant LIMIT represents "LIMIT ALL", which we
+ * treat the same as no limit (ie, expect to retrieve all
+ * the tuples).
+ */
+ if (!limitc->constisnull && count > 0)
{
- Const *limitc = (Const *) parse->limitCount;
- int count = (int) (limitc->constvalue);
-
- /*
- * The constant can legally be either 0 ("ALL") or a
- * positive integer. If it is not ALL, we also need
- * to consider the OFFSET part of LIMIT.
- */
- if (count > 0)
+ limit_fraction = (double) count;
+ /* We must also consider the OFFSET, if present */
+ if (parse->limitOffset != NULL)
{
- tuple_fraction = (double) count;
- if (parse->limitOffset != NULL)
+ if (IsA(parse->limitOffset, Const))
+ {
+ int32 offset;
+
+ limitc = (Const *) parse->limitOffset;
+ offset = DatumGetInt32(limitc->constvalue);
+ if (!limitc->constisnull && offset > 0)
+ limit_fraction += (double) offset;
+ }
+ else
{
- if (IsA(parse->limitOffset, Const))
- {
- int offset;
-
- limitc = (Const *) parse->limitOffset;
- offset = (int) (limitc->constvalue);
- if (offset > 0)
- tuple_fraction += (double) offset;
- }
- else
- {
- /* It's a PARAM ... punt ... */
- tuple_fraction = 0.10;
- }
+ /* OFFSET is an expression ... punt ... */
+ limit_fraction = 0.10;
}
}
}
+ }
+ else
+ {
+ /* LIMIT is an expression ... punt ... */
+ limit_fraction = 0.10;
+ }
+
+ if (limit_fraction > 0.0)
+ {
+ /*
+ * If we have absolute limits from both caller and LIMIT,
+ * use the smaller value; if one is fractional and the
+ * other absolute, treat the fraction as a fraction of the
+ * absolute value; else we can multiply the two fractions
+ * together.
+ */
+ if (tuple_fraction >= 1.0)
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* both absolute */
+ tuple_fraction = Min(tuple_fraction, limit_fraction);
+ }
+ else
+ {
+ /* caller absolute, limit fractional */
+ tuple_fraction *= limit_fraction;
+ if (tuple_fraction < 1.0)
+ tuple_fraction = 1.0;
+ }
+ }
+ else if (tuple_fraction > 0.0)
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* caller fractional, limit absolute */
+ tuple_fraction *= limit_fraction;
+ if (tuple_fraction < 1.0)
+ tuple_fraction = 1.0;
+ }
+ else
+ {
+ /* both fractional */
+ tuple_fraction *= limit_fraction;
+ }
+ }
else
{
-
- /*
- * COUNT is a PARAM ... don't know exactly what the
- * limit will be, but for lack of a better idea assume
- * 10% of the plan's result is wanted.
- */
- tuple_fraction = 0.10;
+ /* no info from caller, just use limit */
+ tuple_fraction = limit_fraction;
}
}
-
- /*
- * Check for a retrieve-into-portal, ie DECLARE CURSOR.
- *
- * We have no real idea how many tuples the user will ultimately
- * FETCH from a cursor, but it seems a good bet that he
- * doesn't want 'em all. Optimize for 10% retrieval (you
- * gotta better number?)
- */
- if (parse->isPortal)
- tuple_fraction = 0.10;
}
/*
- * Adjust tuple_fraction if we see that we are going to apply
- * grouping/aggregation/etc. This is not overridable by the
- * caller, since it reflects plan actions that this routine will
- * certainly take, not assumptions about context.
+ * With grouping or aggregation, the tuple fraction to pass to
+ * query_planner() may be different from what it is at top level.
*/
+ sub_tuple_fraction = tuple_fraction;
+
if (parse->groupClause)
{
-
/*
* In GROUP BY mode, we have the little problem that we don't
* really know how many input tuples will be needed to make a
* amounts to assuming that all the groups are about the same
* size).
*/
- if (tuple_fraction >= 1.0)
- tuple_fraction = 0.25;
+ if (sub_tuple_fraction >= 1.0)
+ sub_tuple_fraction = 0.25;
/*
* If both GROUP BY and ORDER BY are specified, we will need
* two levels of sort --- and, therefore, certainly need to
* read all the input tuples --- unless ORDER BY is a subset
- * of GROUP BY. (Although we are comparing non-canonicalized
- * pathkeys here, it should be OK since they will both contain
- * only single-element sublists at this point. See
- * pathkeys.c.)
+ * of GROUP BY. (We have not yet canonicalized the pathkeys,
+ * so must use the slower noncanonical comparison method.)
*/
if (parse->groupClause && parse->sortClause &&
- !pathkeys_contained_in(sort_pathkeys, group_pathkeys))
- tuple_fraction = 0.0;
+ !noncanonical_pathkeys_contained_in(sort_pathkeys,
+ group_pathkeys))
+ sub_tuple_fraction = 0.0;
}
else if (parse->hasAggs)
{
-
/*
* Ungrouped aggregate will certainly want all the input
* tuples.
*/
- tuple_fraction = 0.0;
+ sub_tuple_fraction = 0.0;
}
else if (parse->distinctClause)
{
-
/*
* SELECT DISTINCT, like GROUP, will absorb an unpredictable
* number of input tuples per output tuple. Handle the same
* way.
*/
- if (tuple_fraction >= 1.0)
- tuple_fraction = 0.25;
+ if (sub_tuple_fraction >= 1.0)
+ sub_tuple_fraction = 0.25;
}
- /* Generate the (sub) plan */
- result_plan = query_planner(parse,
- sub_tlist,
- (List *) parse->qual,
- tuple_fraction);
+ /*
+ * Generate the best unsorted and presorted paths for this Query
+ * (but note there may not be any presorted path).
+ */
+ query_planner(parse, sub_tlist, sub_tuple_fraction,
+ &cheapest_path, &sorted_path);
/*
- * query_planner returns actual sort order (which is not
- * necessarily what we requested) in query_pathkeys.
+ * We couldn't canonicalize group_pathkeys and sort_pathkeys
+ * before running query_planner(), so do it now.
*/
- current_pathkeys = parse->query_pathkeys;
- }
+ group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
+ sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
- /* query_planner returns NULL if it thinks plan is bogus */
- if (!result_plan)
- elog(ERROR, "union_planner: failed to create plan");
+ /*
+ * Consider whether we might want to use hashed grouping.
+ */
+ if (parse->groupClause)
+ {
+ List *groupExprs;
+ double cheapest_path_rows;
+ int cheapest_path_width;
- /*
- * We couldn't canonicalize group_pathkeys and sort_pathkeys before
- * running query_planner(), so do it now.
- */
- group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
- sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
+ /*
+ * Beware in this section of the possibility that
+ * cheapest_path->parent is NULL. This could happen if user
+ * does something silly like SELECT 'foo' GROUP BY 1;
+ */
+ if (cheapest_path->parent)
+ {
+ cheapest_path_rows = cheapest_path->parent->rows;
+ cheapest_path_width = cheapest_path->parent->width;
+ }
+ else
+ {
+ cheapest_path_rows = 1; /* assume non-set result */
+ cheapest_path_width = 100; /* arbitrary */
+ }
- /*
- * If we have a GROUP BY clause, insert a group node (plus the
- * appropriate sort node, if necessary).
- */
- if (parse->groupClause)
- {
- bool tuplePerGroup;
- List *group_tlist;
- bool is_sorted;
+ /*
+ * Always estimate the number of groups. We can't do this
+ * until after running query_planner(), either.
+ */
+ groupExprs = get_sortgrouplist_exprs(parse->groupClause,
+ parse->targetList);
+ dNumGroups = estimate_num_groups(parse,
+ groupExprs,
+ cheapest_path_rows);
+ /* Also want it as a long int --- but 'ware overflow! */
+ numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
+
+ /*
+ * Check can't-do-it conditions, including whether the
+ * grouping operators are hashjoinable.
+ *
+ * Executor doesn't support hashed aggregation with DISTINCT
+ * aggregates. (Doing so would imply storing *all* the input
+ * values in the hash table, which seems like a certain
+ * loser.)
+ */
+ if (!enable_hashagg || !hash_safe_grouping(parse))
+ use_hashed_grouping = false;
+ else if (parse->hasAggs &&
+ (contain_distinct_agg_clause((Node *) tlist) ||
+ contain_distinct_agg_clause(parse->havingQual)))
+ use_hashed_grouping = false;
+ else
+ {
+ /*
+ * Use hashed grouping if (a) we think we can fit the
+ * hashtable into work_mem, *and* (b) the estimated cost is
+ * no more than doing it the other way. While avoiding
+ * the need for sorted input is usually a win, the fact
+ * that the output won't be sorted may be a loss; so we
+ * need to do an actual cost comparison.
+ *
+ * In most cases we have no good way to estimate the size of
+ * the transition value needed by an aggregate;
+ * arbitrarily assume it is 100 bytes. Also set the
+ * overhead per hashtable entry at 64 bytes.
+ */
+ int hashentrysize = cheapest_path_width + 64 + numAggs * 100;
+
+ if (hashentrysize * dNumGroups <= work_mem * 1024L)
+ {
+ /*
+ * Okay, do the cost comparison. We need to consider
+ * cheapest_path + hashagg [+ final sort] versus
+ * either cheapest_path [+ sort] + group or agg [+
+ * final sort] or presorted_path + group or agg [+
+ * final sort] where brackets indicate a step that may
+ * not be needed. We assume query_planner() will have
+ * returned a presorted path only if it's a winner
+ * compared to cheapest_path for this purpose.
+ *
+ * These path variables are dummies that just hold cost
+ * fields; we don't make actual Paths for these steps.
+ */
+ Path hashed_p;
+ Path sorted_p;
+
+ cost_agg(&hashed_p, parse,
+ AGG_HASHED, numAggs,
+ numGroupCols, dNumGroups,
+ cheapest_path->startup_cost,
+ cheapest_path->total_cost,
+ cheapest_path_rows);
+ /* Result of hashed agg is always unsorted */
+ if (sort_pathkeys)
+ cost_sort(&hashed_p, parse, sort_pathkeys,
+ hashed_p.total_cost,
+ dNumGroups,
+ cheapest_path_width);
+
+ if (sorted_path)
+ {
+ sorted_p.startup_cost = sorted_path->startup_cost;
+ sorted_p.total_cost = sorted_path->total_cost;
+ current_pathkeys = sorted_path->pathkeys;
+ }
+ else
+ {
+ sorted_p.startup_cost = cheapest_path->startup_cost;
+ sorted_p.total_cost = cheapest_path->total_cost;
+ current_pathkeys = cheapest_path->pathkeys;
+ }
+ if (!pathkeys_contained_in(group_pathkeys,
+ current_pathkeys))
+ {
+ cost_sort(&sorted_p, parse, group_pathkeys,
+ sorted_p.total_cost,
+ cheapest_path_rows,
+ cheapest_path_width);
+ current_pathkeys = group_pathkeys;
+ }
+ if (parse->hasAggs)
+ cost_agg(&sorted_p, parse,
+ AGG_SORTED, numAggs,
+ numGroupCols, dNumGroups,
+ sorted_p.startup_cost,
+ sorted_p.total_cost,
+ cheapest_path_rows);
+ else
+ cost_group(&sorted_p, parse,
+ numGroupCols, dNumGroups,
+ sorted_p.startup_cost,
+ sorted_p.total_cost,
+ cheapest_path_rows);
+ /* The Agg or Group node will preserve ordering */
+ if (sort_pathkeys &&
+ !pathkeys_contained_in(sort_pathkeys,
+ current_pathkeys))
+ {
+ cost_sort(&sorted_p, parse, sort_pathkeys,
+ sorted_p.total_cost,
+ dNumGroups,
+ cheapest_path_width);
+ }
+
+ /*
+ * Now make the decision using the top-level tuple
+ * fraction. First we have to convert an absolute
+ * count (LIMIT) into fractional form.
+ */
+ if (tuple_fraction >= 1.0)
+ tuple_fraction /= dNumGroups;
+
+ if (compare_fractional_path_costs(&hashed_p, &sorted_p,
+ tuple_fraction) < 0)
+ {
+ /* Hashed is cheaper, so use it */
+ use_hashed_grouping = true;
+ }
+ }
+ }
+ }
/*
- * Decide whether how many tuples per group the Group node needs
- * to return. (Needs only one tuple per group if no aggregate is
- * present. Otherwise, need every tuple from the group to do the
- * aggregation.) Note tuplePerGroup is named backwards :-(
+ * Select the best path and create a plan to execute it.
+ *
+ * If we are doing hashed grouping, we will always read all the input
+ * tuples, so use the cheapest-total path. Otherwise, trust
+ * query_planner's decision about which to use.
*/
- tuplePerGroup = parse->hasAggs;
+ if (sorted_path && !use_hashed_grouping)
+ {
+ result_plan = create_plan(parse, sorted_path);
+ current_pathkeys = sorted_path->pathkeys;
+ }
+ else
+ {
+ result_plan = create_plan(parse, cheapest_path);
+ current_pathkeys = cheapest_path->pathkeys;
+ }
/*
- * If there are aggregates then the Group node should just return
- * the same set of vars as the subplan did (but we can exclude any
- * GROUP BY expressions). If there are no aggregates then the
- * Group node had better compute the final tlist.
+ * create_plan() returns a plan with just a "flat" tlist of
+ * required Vars. Usually we need to insert the sub_tlist as the
+ * tlist of the top plan node. However, we can skip that if we
+ * determined that whatever query_planner chose to return will be
+ * good enough.
*/
- if (parse->hasAggs)
- group_tlist = flatten_tlist(result_plan->targetlist);
+ if (need_tlist_eval)
+ {
+ /*
+ * If the top-level plan node is one that cannot do expression
+ * evaluation, we must insert a Result node to project the
+ * desired tlist.
+ */
+ if (!is_projection_capable_plan(result_plan))
+ {
+ result_plan = (Plan *) make_result(sub_tlist, NULL,
+ result_plan);
+ }
+ else
+ {
+ /*
+ * Otherwise, just replace the subplan's flat tlist with
+ * the desired tlist.
+ */
+ result_plan->targetlist = sub_tlist;
+ }
+
+ /*
+ * Also, account for the cost of evaluation of the sub_tlist.
+ *
+ * Up to now, we have only been dealing with "flat" tlists,
+ * containing just Vars. So their evaluation cost is zero
+ * according to the model used by cost_qual_eval() (or if you
+ * prefer, the cost is factored into cpu_tuple_cost). Thus we
+ * can avoid accounting for tlist cost throughout
+ * query_planner() and subroutines. But now we've inserted a
+ * tlist that might contain actual operators, sub-selects, etc
+ * --- so we'd better account for its cost.
+ *
+ * Below this point, any tlist eval cost for added-on nodes
+ * should be accounted for as we create those nodes.
+ * Presently, of the node types we can add on, only Agg and
+ * Group project new tlists (the rest just copy their input
+ * tuples) --- so make_agg() and make_group() are responsible
+ * for computing the added cost.
+ */
+ cost_qual_eval(&tlist_cost, sub_tlist);
+ result_plan->startup_cost += tlist_cost.startup;
+ result_plan->total_cost += tlist_cost.startup +
+ tlist_cost.per_tuple * result_plan->plan_rows;
+ }
else
- group_tlist = tlist;
+ {
+ /*
+ * Since we're using query_planner's tlist and not the one
+ * make_subplanTargetList calculated, we have to refigure any
+ * grouping-column indexes make_subplanTargetList computed.
+ */
+ locate_grouping_columns(parse, tlist, result_plan->targetlist,
+ groupColIdx);
+ }
/*
- * Figure out whether the path result is already ordered the way
- * we need it --- if so, no need for an explicit sort step.
+ * Insert AGG or GROUP node if needed, plus an explicit sort step
+ * if necessary.
+ *
+ * HAVING clause, if any, becomes qual of the Agg node
*/
- if (pathkeys_contained_in(group_pathkeys, current_pathkeys))
+ if (use_hashed_grouping)
{
- is_sorted = true; /* no sort needed now */
- /* current_pathkeys remains unchanged */
+ /* Hashed aggregate plan --- no sort needed */
+ result_plan = (Plan *) make_agg(parse,
+ tlist,
+ (List *) parse->havingQual,
+ AGG_HASHED,
+ numGroupCols,
+ groupColIdx,
+ numGroups,
+ numAggs,
+ result_plan);
+ /* Hashed aggregation produces randomly-ordered results */
+ current_pathkeys = NIL;
}
- else
+ else if (parse->hasAggs)
{
+ /* Plain aggregate plan --- sort if needed */
+ AggStrategy aggstrategy;
+
+ if (parse->groupClause)
+ {
+ if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
+ {
+ result_plan = (Plan *)
+ make_sort_from_groupcols(parse,
+ parse->groupClause,
+ groupColIdx,
+ result_plan);
+ current_pathkeys = group_pathkeys;
+ }
+ aggstrategy = AGG_SORTED;
+
+ /*
+ * The AGG node will not change the sort ordering of its
+ * groups, so current_pathkeys describes the result too.
+ */
+ }
+ else
+ {
+ aggstrategy = AGG_PLAIN;
+ /* Result will be only one row anyway; no sort order */
+ current_pathkeys = NIL;
+ }
+ result_plan = (Plan *) make_agg(parse,
+ tlist,
+ (List *) parse->havingQual,
+ aggstrategy,
+ numGroupCols,
+ groupColIdx,
+ numGroups,
+ numAggs,
+ result_plan);
+ }
+ else
+ {
/*
- * We will need to do an explicit sort by the GROUP BY clause.
- * make_groupplan will do the work, but set current_pathkeys
- * to indicate the resulting order.
+ * If there are no Aggs, we shouldn't have any HAVING qual
+ * anymore
*/
- is_sorted = false;
- current_pathkeys = group_pathkeys;
- }
+ Assert(parse->havingQual == NULL);
- result_plan = make_groupplan(group_tlist,
- tuplePerGroup,
- parse->groupClause,
- groupColIdx,
- is_sorted,
- result_plan);
- }
+ /*
+ * If we have a GROUP BY clause, insert a group node (plus the
+ * appropriate sort node, if necessary).
+ */
+ if (parse->groupClause)
+ {
+ /*
+ * Add an explicit sort if we couldn't make the path come
+ * out the way the GROUP node needs it.
+ */
+ if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
+ {
+ result_plan = (Plan *)
+ make_sort_from_groupcols(parse,
+ parse->groupClause,
+ groupColIdx,
+ result_plan);
+ current_pathkeys = group_pathkeys;
+ }
- /*
- * If aggregate is present, insert the Agg node
- *
- * HAVING clause, if any, becomes qual of the Agg node
- */
- if (parse->hasAggs)
- {
- result_plan = (Plan *) make_agg(tlist,
- (List *) parse->havingQual,
- result_plan);
- /* Note: Agg does not affect any existing sort order of the tuples */
- }
+ result_plan = (Plan *) make_group(parse,
+ tlist,
+ numGroupCols,
+ groupColIdx,
+ dNumGroups,
+ result_plan);
+ /* The Group node won't change sort ordering */
+ }
+ }
+ } /* end of if (setOperations) */
/*
* If we were not able to make the plan come out in the right order,
if (parse->sortClause)
{
if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
- result_plan = make_sortplan(tlist, result_plan,
- parse->sortClause);
+ {
+ result_plan = (Plan *)
+ make_sort_from_sortclauses(parse,
+ parse->sortClause,
+ result_plan);
+ current_pathkeys = sort_pathkeys;
+ }
}
/*
- * Finally, if there is a DISTINCT clause, add the UNIQUE node.
+ * If there is a DISTINCT clause, add the UNIQUE node.
*/
if (parse->distinctClause)
{
- result_plan = (Plan *) make_unique(tlist, result_plan,
- parse->distinctClause);
+ result_plan = (Plan *) make_unique(result_plan, parse->distinctClause);
+
+ /*
+ * If there was grouping or aggregation, leave plan_rows as-is
+ * (ie, assume the result was already mostly unique). If not,
+ * it's reasonable to assume the UNIQUE filter has effects
+ * comparable to GROUP BY.
+ */
+ if (!parse->groupClause && !parse->hasAggs)
+ {
+ List *distinctExprs;
+
+ distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
+ parse->targetList);
+ result_plan->plan_rows = estimate_num_groups(parse,
+ distinctExprs,
+ result_plan->plan_rows);
+ }
}
+ /*
+ * Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
+ */
+ if (parse->limitOffset || parse->limitCount)
+ {
+ result_plan = (Plan *) make_limit(result_plan,
+ parse->limitOffset,
+ parse->limitCount);
+ }
+
+ /*
+ * Return the actual output ordering in query_pathkeys for possible
+ * use by an outer query level.
+ */
+ parse->query_pathkeys = current_pathkeys;
+
return result_plan;
}
+/*
+ * hash_safe_grouping - are grouping operators hashable?
+ *
+ * We assume hashed aggregation will work if the datatype's equality operator
+ * is marked hashjoinable.
+ */
+static bool
+hash_safe_grouping(Query *parse)
+{
+ ListCell *gl;
+
+ foreach(gl, parse->groupClause)
+ {
+ GroupClause *grpcl = (GroupClause *) lfirst(gl);
+ TargetEntry *tle = get_sortgroupclause_tle(grpcl, parse->targetList);
+ Operator optup;
+ bool oprcanhash;
+
+ optup = equality_oper(tle->resdom->restype, true);
+ if (!optup)
+ return false;
+ oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
+ ReleaseSysCache(optup);
+ if (!oprcanhash)
+ return false;
+ }
+ return true;
+}
+
/*---------------
* make_subplanTargetList
* Generate appropriate target list when grouping is required.
*
- * When union_planner inserts Aggregate and/or Group plan nodes above
+ * When grouping_planner inserts Aggregate or Group plan nodes above
* the result of query_planner, we typically want to pass a different
* target list to query_planner than the outer plan nodes should have.
* This routine generates the correct target list for the subplan.
* where the a+b target will be used by the Sort/Group steps, and the
* other targets will be used for computing the final results. (In the
* above example we could theoretically suppress the a and b targets and
- * use only a+b, but it's not really worth the trouble.)
+ * pass down only c,d,a+b, but it's not really worth the trouble to
+ * eliminate simple var references from the subplan. We will avoid doing
+ * the extra computation to recompute a+b at the outer level; see
+ * replace_vars_with_subplan_refs() in setrefs.c.)
+ *
+ * If we are grouping or aggregating, *and* there are no non-Var grouping
+ * expressions, then the returned tlist is effectively dummy; we do not
+ * need to force it to be evaluated, because all the Vars it contains
+ * should be present in the output of query_planner anyway.
*
* 'parse' is the query being processed.
* 'tlist' is the query's target list.
* 'groupColIdx' receives an array of column numbers for the GROUP BY
- * expressions (if there are any) in the subplan's target list.
+ * expressions (if there are any) in the subplan's target list.
+ * 'need_tlist_eval' is set true if we really need to evaluate the
+ * result tlist.
*
* The result is the targetlist to be passed to the subplan.
*---------------
static List *
make_subplanTargetList(Query *parse,
List *tlist,
- AttrNumber **groupColIdx)
+ AttrNumber **groupColIdx,
+ bool *need_tlist_eval)
{
List *sub_tlist;
List *extravars;
* If we're not grouping or aggregating, nothing to do here;
* query_planner should receive the unmodified target list.
*/
- if (!parse->hasAggs && !parse->groupClause && !parse->havingQual)
+ if (!parse->hasAggs && !parse->groupClause)
+ {
+ *need_tlist_eval = true;
return tlist;
+ }
/*
* Otherwise, start with a "flattened" tlist (having just the vars
sub_tlist = flatten_tlist(tlist);
extravars = pull_var_clause(parse->havingQual, false);
sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
- freeList(extravars);
+ list_free(extravars);
+ *need_tlist_eval = false; /* only eval if not flat tlist */
/*
* If grouping, create sub_tlist entries for all GROUP BY expressions
* already), and make an array showing where the group columns are in
* the sub_tlist.
*/
- numCols = length(parse->groupClause);
+ numCols = list_length(parse->groupClause);
if (numCols > 0)
{
int keyno = 0;
AttrNumber *grpColIdx;
- List *gl;
+ ListCell *gl;
grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
*groupColIdx = grpColIdx;
foreach(gl, parse->groupClause)
{
- GroupClause *grpcl = (GroupClause *) lfirst(gl);
- Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
- TargetEntry *te = NULL;
- List *sl;
+ GroupClause *grpcl = (GroupClause *) lfirst(gl);
+ Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
+ TargetEntry *te = NULL;
+ ListCell *sl;
/* Find or make a matching sub_tlist entry */
foreach(sl, sub_tlist)
}
if (!sl)
{
- te = makeTargetEntry(makeResdom(length(sub_tlist) + 1,
+ te = makeTargetEntry(makeResdom(list_length(sub_tlist) + 1,
exprType(groupexpr),
exprTypmod(groupexpr),
NULL,
false),
- groupexpr);
+ (Expr *) groupexpr);
sub_tlist = lappend(sub_tlist, te);
+ *need_tlist_eval = true; /* it's not flat anymore */
}
/* and save its resno */
}
/*
- * make_groupplan
- * Add a Group node for GROUP BY processing.
- * If we couldn't make the subplan produce presorted output for grouping,
- * first add an explicit Sort node.
+ * locate_grouping_columns
+ * Locate grouping columns in the tlist chosen by query_planner.
+ *
+ * This is only needed if we don't use the sub_tlist chosen by
+ * make_subplanTargetList. We have to forget the column indexes found
+ * by that routine and re-locate the grouping vars in the real sub_tlist.
*/
-static Plan *
-make_groupplan(List *group_tlist,
- bool tuplePerGroup,
- List *groupClause,
- AttrNumber *grpColIdx,
- bool is_presorted,
- Plan *subplan)
+static void
+locate_grouping_columns(Query *parse,
+ List *tlist,
+ List *sub_tlist,
+ AttrNumber *groupColIdx)
{
- int numCols = length(groupClause);
+ int keyno = 0;
+ ListCell *gl;
- if (!is_presorted)
+ /*
+ * No work unless grouping.
+ */
+ if (!parse->groupClause)
{
+ Assert(groupColIdx == NULL);
+ return;
+ }
+ Assert(groupColIdx != NULL);
- /*
- * The Sort node always just takes a copy of the subplan's tlist
- * plus ordering information. (This might seem inefficient if the
- * subplan contains complex GROUP BY expressions, but in fact Sort
- * does not evaluate its targetlist --- it only outputs the same
- * tuples in a new order. So the expressions we might be copying
- * are just dummies with no extra execution cost.)
- */
- List *sort_tlist = new_unsorted_tlist(subplan->targetlist);
- int keyno = 0;
- List *gl;
+ foreach(gl, parse->groupClause)
+ {
+ GroupClause *grpcl = (GroupClause *) lfirst(gl);
+ Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
+ TargetEntry *te = NULL;
+ ListCell *sl;
- foreach(gl, groupClause)
+ foreach(sl, sub_tlist)
{
- GroupClause *grpcl = (GroupClause *) lfirst(gl);
- TargetEntry *te = nth(grpColIdx[keyno] - 1, sort_tlist);
- Resdom *resdom = te->resdom;
-
- /*
- * Check for the possibility of duplicate group-by clauses ---
- * the parser should have removed 'em, but the Sort executor
- * will get terribly confused if any get through!
- */
- if (resdom->reskey == 0)
- {
- /* OK, insert the ordering info needed by the executor. */
- resdom->reskey = ++keyno;
- resdom->reskeyop = get_opcode(grpcl->sortop);
- }
+ te = (TargetEntry *) lfirst(sl);
+ if (equal(groupexpr, te->expr))
+ break;
}
+ if (!sl)
+ elog(ERROR, "failed to locate grouping columns");
- Assert(keyno > 0);
-
- subplan = (Plan *) make_sort(sort_tlist, subplan, keyno);
+ groupColIdx[keyno++] = te->resdom->resno;
}
-
- return (Plan *) make_group(group_tlist, tuplePerGroup, numCols,
- grpColIdx, subplan);
}
/*
- * make_sortplan
- * Add a Sort node to implement an explicit ORDER BY clause.
+ * postprocess_setop_tlist
+ * Fix up targetlist returned by plan_set_operations().
+ *
+ * We need to transpose sort key info from the orig_tlist into new_tlist.
+ * NOTE: this would not be good enough if we supported resjunk sort keys
+ * for results of set operations --- then, we'd need to project a whole
+ * new tlist to evaluate the resjunk columns. For now, just ereport if we
+ * find any resjunk columns in orig_tlist.
*/
-static Plan *
-make_sortplan(List *tlist, Plan *plannode, List *sortcls)
+static List *
+postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
{
- List *sort_tlist;
- List *i;
- int keyno = 0;
-
- /*
- * First make a copy of the tlist so that we don't corrupt the
- * original.
- */
- sort_tlist = new_unsorted_tlist(tlist);
+ ListCell *l;
+ ListCell *orig_tlist_item = list_head(orig_tlist);
- foreach(i, sortcls)
+ foreach(l, new_tlist)
{
- SortClause *sortcl = (SortClause *) lfirst(i);
- TargetEntry *tle = get_sortgroupclause_tle(sortcl, sort_tlist);
- Resdom *resdom = tle->resdom;
-
- /*
- * Check for the possibility of duplicate order-by clauses --- the
- * parser should have removed 'em, but the executor will get
- * terribly confused if any get through!
- */
- if (resdom->reskey == 0)
- {
- /* OK, insert the ordering info needed by the executor. */
- resdom->reskey = ++keyno;
- resdom->reskeyop = get_opcode(sortcl->sortop);
- }
+ TargetEntry *new_tle = (TargetEntry *) lfirst(l);
+ TargetEntry *orig_tle;
+
+ /* ignore resjunk columns in setop result */
+ if (new_tle->resdom->resjunk)
+ continue;
+
+ Assert(orig_tlist_item != NULL);
+ orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
+ orig_tlist_item = lnext(orig_tlist_item);
+ if (orig_tle->resdom->resjunk) /* should not happen */
+ elog(ERROR, "resjunk output columns are not implemented");
+ Assert(new_tle->resdom->resno == orig_tle->resdom->resno);
+ Assert(new_tle->resdom->restype == orig_tle->resdom->restype);
+ new_tle->resdom->ressortgroupref = orig_tle->resdom->ressortgroupref;
}
-
- Assert(keyno > 0);
-
- return (Plan *) make_sort(sort_tlist, plannode, keyno);
+ if (orig_tlist_item != NULL)
+ elog(ERROR, "resjunk output columns are not implemented");
+ return new_tlist;
}
projects / postgresql / blobdiff