* planner.c
* The query optimizer external interface.
*
- * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.168 2004/04/07 18:17:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.224 2007/11/15 21:14:36 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <limits.h>
#include "catalog/pg_operator.h"
-#include "catalog/pg_type.h"
#include "executor/executor.h"
+#include "executor/nodeAgg.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/subselect.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
-#include "parser/analyze.h"
-#include "parser/parsetree.h"
+#ifdef OPTIMIZER_DEBUG
+#include "nodes/print.h"
+#endif
#include "parser/parse_expr.h"
#include "parser/parse_oper.h"
-#include "utils/selfuncs.h"
+#include "parser/parsetree.h"
+#include "utils/lsyscache.h"
#include "utils/syscache.h"
+/* Hook for plugins to get control in planner() */
+planner_hook_type planner_hook = NULL;
+
+
/* 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,
+#define EXPRKIND_QUAL 0
+#define EXPRKIND_TARGET 1
+#define EXPRKIND_RTFUNC 2
+#define EXPRKIND_VALUES 3
+#define EXPRKIND_LIMIT 4
+#define EXPRKIND_ININFO 5
+#define EXPRKIND_APPINFO 6
+
+
+static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
+static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
+static Plan *inheritance_planner(PlannerInfo *root);
+static Plan *grouping_planner(PlannerInfo *root, double tuple_fraction);
+static bool is_dummy_plan(Plan *plan);
+static double preprocess_limit(PlannerInfo *root,
+ double tuple_fraction,
+ int64 *offset_est, int64 *count_est);
+static Oid *extract_grouping_ops(List *groupClause);
+static bool choose_hashed_grouping(PlannerInfo *root,
+ double tuple_fraction, double limit_tuples,
+ Path *cheapest_path, Path *sorted_path,
+ Oid *groupOperators, double dNumGroups,
+ AggClauseCounts *agg_counts);
+static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
AttrNumber **groupColIdx, bool *need_tlist_eval);
-static void locate_grouping_columns(Query *parse,
+static void locate_grouping_columns(PlannerInfo *root,
List *tlist,
List *sub_tlist,
AttrNumber *groupColIdx);
*
* Query optimizer entry point
*
+ * To support loadable plugins that monitor or modify planner behavior,
+ * we provide a hook variable that lets a plugin get control before and
+ * after the standard planning process. The plugin would normally call
+ * standard_planner().
+ *
+ * Note to plugin authors: standard_planner() scribbles on its Query input,
+ * so you'd better copy that data structure if you want to plan more than once.
+ *
*****************************************************************************/
-Plan *
-planner(Query *parse, bool isCursor, int cursorOptions)
+PlannedStmt *
+planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
+{
+ PlannedStmt *result;
+
+ if (planner_hook)
+ result = (*planner_hook) (parse, cursorOptions, boundParams);
+ else
+ result = standard_planner(parse, cursorOptions, boundParams);
+ return result;
+}
+
+PlannedStmt *
+standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
+ PlannedStmt *result;
+ PlannerGlobal *glob;
double tuple_fraction;
- Plan *result_plan;
- Index save_PlannerQueryLevel;
- List *save_PlannerParamList;
+ PlannerInfo *root;
+ Plan *top_plan;
+ ListCell *lp,
+ *lr;
+
+ /* Cursor options may come from caller or from DECLARE CURSOR stmt */
+ if (parse->utilityStmt &&
+ IsA(parse->utilityStmt, DeclareCursorStmt))
+ cursorOptions |= ((DeclareCursorStmt *) parse->utilityStmt)->options;
/*
- * The planner can be called recursively (an example is when
- * eval_const_expressions tries to pre-evaluate an SQL function). So,
- * these global state variables must be saved and restored.
- *
- * These vars cannot be moved into the Query structure since their whole
- * purpose is communication across multiple sub-Queries.
- *
- * 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.
+ * Set up global state for this planner invocation. This data is needed
+ * across all levels of sub-Query that might exist in the given command,
+ * so we keep it in a separate struct that's linked to by each per-Query
+ * PlannerInfo.
*/
- save_PlannerQueryLevel = PlannerQueryLevel;
- save_PlannerParamList = PlannerParamList;
+ glob = makeNode(PlannerGlobal);
- /* Initialize state for handling outer-level references and params */
- PlannerQueryLevel = 0; /* will be 1 in top-level subquery_planner */
- PlannerParamList = NIL;
+ glob->boundParams = boundParams;
+ glob->paramlist = NIL;
+ glob->subplans = NIL;
+ glob->subrtables = NIL;
+ glob->rewindPlanIDs = NULL;
+ glob->finalrtable = NIL;
+ glob->relationOids = NIL;
+ glob->transientPlan = false;
/* Determine what fraction of the plan is likely to be scanned */
- if (isCursor)
+ if (cursorOptions & CURSOR_OPT_FAST_PLAN)
{
/*
- * 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?)
+ * 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;
}
}
/* primary planning entry point (may recurse for subqueries) */
- result_plan = subquery_planner(parse, tuple_fraction);
-
- Assert(PlannerQueryLevel == 0);
+ top_plan = subquery_planner(glob, parse, 1, tuple_fraction, &root);
/*
* 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))
+ if (cursorOptions & CURSOR_OPT_SCROLL)
{
- if (!ExecSupportsBackwardScan(result_plan))
- result_plan = materialize_finished_plan(result_plan);
+ if (!ExecSupportsBackwardScan(top_plan))
+ top_plan = materialize_finished_plan(top_plan);
}
- /* executor wants to know total number of Params used overall */
- result_plan->nParamExec = length(PlannerParamList);
-
/* final cleanup of the plan */
- set_plan_references(result_plan, parse->rtable);
+ Assert(glob->finalrtable == NIL);
+ top_plan = set_plan_references(glob, top_plan, root->parse->rtable);
+ /* ... and the subplans (both regular subplans and initplans) */
+ Assert(list_length(glob->subplans) == list_length(glob->subrtables));
+ forboth(lp, glob->subplans, lr, glob->subrtables)
+ {
+ Plan *subplan = (Plan *) lfirst(lp);
+ List *subrtable = (List *) lfirst(lr);
- /* restore state for outer planner, if any */
- PlannerQueryLevel = save_PlannerQueryLevel;
- PlannerParamList = save_PlannerParamList;
+ lfirst(lp) = set_plan_references(glob, subplan, subrtable);
+ }
- return result_plan;
+ /* build the PlannedStmt result */
+ result = makeNode(PlannedStmt);
+
+ result->commandType = parse->commandType;
+ result->canSetTag = parse->canSetTag;
+ result->transientPlan = glob->transientPlan;
+ result->planTree = top_plan;
+ result->rtable = glob->finalrtable;
+ result->resultRelations = root->resultRelations;
+ result->utilityStmt = parse->utilityStmt;
+ result->intoClause = parse->intoClause;
+ result->subplans = glob->subplans;
+ result->rewindPlanIDs = glob->rewindPlanIDs;
+ result->returningLists = root->returningLists;
+ result->rowMarks = parse->rowMarks;
+ result->relationOids = glob->relationOids;
+ result->nParamExec = list_length(glob->paramlist);
+
+ return result;
}
* Invokes the planner on a subquery. We recurse to here for each
* sub-SELECT found in the query tree.
*
+ * glob is the global state for the current planner run.
* parse is the querytree produced by the parser & rewriter.
+ * level is the current recursion depth (1 at the top-level Query).
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as explained for grouping_planner, below.
*
+ * If subroot isn't NULL, we pass back the query's final PlannerInfo struct;
+ * among other things this tells the output sort ordering of the plan.
+ *
* Basically, this routine does the stuff that should only be done once
* per Query object. It then calls grouping_planner. At one time,
* grouping_planner could be invoked recursively on the same Query object;
*--------------------
*/
Plan *
-subquery_planner(Query *parse, double tuple_fraction)
+subquery_planner(PlannerGlobal * glob, Query *parse,
+ Index level, double tuple_fraction,
+ PlannerInfo **subroot)
{
- List *saved_initplan = PlannerInitPlan;
- int saved_planid = PlannerPlanId;
- bool hasOuterJoins;
+ int num_old_subplans = list_length(glob->subplans);
+ PlannerInfo *root;
Plan *plan;
List *newHaving;
- List *lst;
-
- /* Set up for a new level of subquery */
- PlannerQueryLevel++;
- PlannerInitPlan = NIL;
+ ListCell *l;
+
+ /* Create a PlannerInfo data structure for this subquery */
+ root = makeNode(PlannerInfo);
+ root->parse = parse;
+ root->glob = glob;
+ root->query_level = level;
+ root->planner_cxt = CurrentMemoryContext;
+ root->init_plans = NIL;
+ root->eq_classes = NIL;
+ root->in_info_list = NIL;
+ root->append_rel_list = 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.
+ * 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);
+ parse->jointree->quals = pull_up_IN_clauses(root,
+ 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);
+ pull_up_subqueries(root, (Node *) parse->jointree, false, 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
+ * 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() and some
+ * other processing. This must be done after we have done
* pull_up_subqueries, of course.
+ *
+ * Note: if reduce_outer_joins manages to eliminate all outer joins,
+ * root->hasOuterJoins is not reset currently. This is OK since its
+ * purpose is merely to suppress unnecessary processing in simple cases.
*/
- parse->hasJoinRTEs = false;
- hasOuterJoins = false;
- foreach(lst, parse->rtable)
+ root->hasJoinRTEs = false;
+ root->hasOuterJoins = false;
+ foreach(l, parse->rtable)
{
- RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
+ RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
if (rte->rtekind == RTE_JOIN)
{
- parse->hasJoinRTEs = true;
+ root->hasJoinRTEs = true;
if (IS_OUTER_JOIN(rte->jointype))
{
- hasOuterJoins = true;
+ root->hasOuterJoins = true;
/* Can quit scanning once we find an outer join */
break;
}
}
}
+ /*
+ * Expand any rangetable entries that are inheritance sets into "append
+ * relations". This can add entries to the rangetable, but they must be
+ * plain base relations not joins, so it's OK (and marginally more
+ * efficient) to do it after checking for join RTEs. We must do it after
+ * pulling up subqueries, else we'd fail to handle inherited tables in
+ * subqueries.
+ */
+ expand_inherited_tables(root);
+
+ /*
+ * Set hasHavingQual to remember if HAVING clause is present. Needed
+ * because preprocess_expression will reduce a constant-true condition to
+ * an empty qual list ... but "HAVING TRUE" is not a semantic no-op.
+ */
+ root->hasHavingQual = (parse->havingQual != NULL);
+
+ /* Clear this flag; might get set in distribute_qual_to_rels */
+ root->hasPseudoConstantQuals = false;
+
/*
* Do expression preprocessing on targetlist and quals.
*/
parse->targetList = (List *)
- preprocess_expression(parse, (Node *) parse->targetList,
+ preprocess_expression(root, (Node *) parse->targetList,
EXPRKIND_TARGET);
- preprocess_qual_conditions(parse, (Node *) parse->jointree);
+ parse->returningList = (List *)
+ preprocess_expression(root, (Node *) parse->returningList,
+ EXPRKIND_TARGET);
- parse->havingQual = preprocess_expression(parse, parse->havingQual,
+ preprocess_qual_conditions(root, (Node *) parse->jointree);
+
+ parse->havingQual = preprocess_expression(root, parse->havingQual,
EXPRKIND_QUAL);
- parse->limitOffset = preprocess_expression(parse, parse->limitOffset,
+ parse->limitOffset = preprocess_expression(root, parse->limitOffset,
EXPRKIND_LIMIT);
- parse->limitCount = preprocess_expression(parse, parse->limitCount,
+ parse->limitCount = preprocess_expression(root, parse->limitCount,
EXPRKIND_LIMIT);
- parse->in_info_list = (List *)
- preprocess_expression(parse, (Node *) parse->in_info_list,
+ root->in_info_list = (List *)
+ preprocess_expression(root, (Node *) root->in_info_list,
EXPRKIND_ININFO);
+ root->append_rel_list = (List *)
+ preprocess_expression(root, (Node *) root->append_rel_list,
+ EXPRKIND_APPINFO);
- /* Also need to preprocess expressions for function RTEs */
- foreach(lst, parse->rtable)
+ /* Also need to preprocess expressions for function and values RTEs */
+ foreach(l, parse->rtable)
{
- RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
+ RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
if (rte->rtekind == RTE_FUNCTION)
- rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
+ rte->funcexpr = preprocess_expression(root, rte->funcexpr,
EXPRKIND_RTFUNC);
+ else if (rte->rtekind == RTE_VALUES)
+ rte->values_lists = (List *)
+ preprocess_expression(root, (Node *) rte->values_lists,
+ EXPRKIND_VALUES);
}
/*
- * A HAVING clause without aggregates is equivalent to a WHERE clause
- * (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.
+ * In some cases we may want to transfer a HAVING clause into WHERE. We
+ * cannot do so if the HAVING clause contains aggregates (obviously) or
+ * volatile functions (since a HAVING clause is supposed to be executed
+ * only once per group). Also, it may be that the clause is so expensive
+ * to execute that we're better off doing it only once per group, despite
+ * the loss of selectivity. This is hard to estimate short of doing the
+ * entire planning process twice, so we use a heuristic: clauses
+ * containing subplans are left in HAVING. Otherwise, we move or copy the
+ * HAVING clause into WHERE, in hopes of eliminating tuples before
+ * aggregation instead of after.
+ *
+ * If the query has explicit grouping then we can simply move such a
+ * clause into WHERE; any group that fails the clause will not be in the
+ * output because none of its tuples will reach the grouping or
+ * aggregation stage. Otherwise we must have a degenerate (variable-free)
+ * HAVING clause, which we put in WHERE so that query_planner() can use it
+ * in a gating Result node, but also keep in HAVING to ensure that we
+ * don't emit a bogus aggregated row. (This could be done better, but it
+ * seems not worth optimizing.)
*
* Note that both havingQual and parse->jointree->quals are in
- * implicitly-ANDed-list form at this point, even though they are
- * declared as Node *.
+ * implicitly-ANDed-list form at this point, even though they are declared
+ * as Node *.
*/
newHaving = NIL;
- foreach(lst, (List *) parse->havingQual)
+ foreach(l, (List *) parse->havingQual)
{
- Node *havingclause = (Node *) lfirst(lst);
+ Node *havingclause = (Node *) lfirst(l);
- if (contain_agg_clause(havingclause))
+ if (contain_agg_clause(havingclause) ||
+ contain_volatile_functions(havingclause) ||
+ contain_subplans(havingclause))
+ {
+ /* keep it in HAVING */
newHaving = lappend(newHaving, havingclause);
- else
+ }
+ else if (parse->groupClause)
+ {
+ /* move it to WHERE */
parse->jointree->quals = (Node *)
lappend((List *) parse->jointree->quals, havingclause);
+ }
+ else
+ {
+ /* put a copy in WHERE, keep it in HAVING */
+ parse->jointree->quals = (Node *)
+ lappend((List *) parse->jointree->quals,
+ copyObject(havingclause));
+ newHaving = lappend(newHaving, havingclause);
+ }
}
parse->havingQual = (Node *) newHaving;
/*
- * 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
+ * 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.
*/
- 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);
+ if (root->hasOuterJoins)
+ reduce_outer_joins(root);
/*
- * Do the main planning. If we have an inherited target relation,
- * that needs special processing, else go straight to
- * grouping_planner.
+ * 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);
+ rt_fetch(parse->resultRelation, parse->rtable)->inh)
+ plan = inheritance_planner(root);
else
- plan = grouping_planner(parse, tuple_fraction);
+ plan = grouping_planner(root, tuple_fraction);
/*
* If any subplans were generated, or if we're inside a subplan, build
- * initPlan list and extParam/allParam sets for plan nodes.
+ * initPlan list and extParam/allParam sets for plan nodes, and attach the
+ * initPlans to the top plan node.
*/
- 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(lst, plan->initPlan)
- {
- SubPlan *initplan = (SubPlan *) lfirst(lst);
-
- plan->extParam = bms_add_members(plan->extParam,
- initplan->plan->extParam);
- initplan_cost += initplan->plan->total_cost;
- }
-
- plan->startup_cost += initplan_cost;
- plan->total_cost += initplan_cost;
- }
+ if (list_length(glob->subplans) != num_old_subplans ||
+ root->query_level > 1)
+ SS_finalize_plan(root, plan);
- /* Return to outer subquery context */
- PlannerQueryLevel--;
- PlannerInitPlan = saved_initplan;
- /* we do NOT restore PlannerPlanId; that's not an oversight! */
+ /* Return internal info if caller wants it */
+ if (subroot)
+ *subroot = root;
return plan;
}
* conditions), or a HAVING clause.
*/
static Node *
-preprocess_expression(Query *parse, Node *expr, int kind)
+preprocess_expression(PlannerInfo *root, Node *expr, int kind)
{
+ /*
+ * Fall out quickly if expression is empty. This occurs often enough to
+ * be worth checking. Note that null->null is the correct conversion for
+ * implicit-AND result format, too.
+ */
+ if (expr == NULL)
+ return NULL;
+
/*
* 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.
+ * else sublinks expanded out from join aliases wouldn't get processed. We
+ * can skip it in VALUES lists, however, since they can't contain any Vars
+ * at all.
*/
- if (parse->hasJoinRTEs)
- expr = flatten_join_alias_vars(parse, expr);
+ if (root->hasJoinRTEs && kind != EXPRKIND_VALUES)
+ expr = flatten_join_alias_vars(root, 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.
+ * Simplify constant expressions.
+ *
+ * Note: this also flattens nested AND and OR expressions into N-argument
+ * form. 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.
*
- * 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.
+ * Because this is a relatively expensive process, we skip it when the
+ * query is trivial, such as "SELECT 2+2;" or "INSERT ... VALUES()". The
+ * expression will only be evaluated once anyway, so no point in
+ * pre-simplifying; we can't execute it any faster than the executor can,
+ * and we will waste cycles copying the tree. Notice however that we
+ * still must do it for quals (to get AND/OR flatness); and if we are in a
+ * subquery we should not assume it will be done only once.
+ *
+ * For VALUES lists we never do this at all, again on the grounds that we
+ * should optimize for one-time evaluation.
+ */
+ if (kind != EXPRKIND_VALUES &&
+ (root->parse->jointree->fromlist != NIL ||
+ kind == EXPRKIND_QUAL ||
+ root->query_level > 1))
+ expr = eval_const_expressions(expr);
+
+ /*
+ * If it's a qual or havingQual, canonicalize it.
*/
if (kind == EXPRKIND_QUAL)
{
#endif
}
- /*
- * Simplify constant expressions.
- */
- expr = eval_const_expressions(expr);
-
/* Expand SubLinks to SubPlans */
- if (parse->hasSubLinks)
- expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
+ if (root->parse->hasSubLinks)
+ expr = SS_process_sublinks(root, expr, (kind == EXPRKIND_QUAL));
/*
- * XXX do not insert anything here unless you have grokked the
- * comments in SS_replace_correlation_vars ...
+ * 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);
+ /* Replace uplevel vars with Param nodes (this IS possible in VALUES) */
+ if (root->query_level > 1)
+ expr = SS_replace_correlation_vars(root, 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,
+ * 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)
* preprocessing work on each qual condition found therein.
*/
static void
-preprocess_qual_conditions(Query *parse, Node *jtnode)
+preprocess_qual_conditions(PlannerInfo *root, Node *jtnode)
{
if (jtnode == NULL)
return;
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
- List *l;
+ ListCell *l;
foreach(l, f->fromlist)
- preprocess_qual_conditions(parse, lfirst(l));
+ preprocess_qual_conditions(root, lfirst(l));
- f->quals = preprocess_expression(parse, f->quals, EXPRKIND_QUAL);
+ f->quals = preprocess_expression(root, f->quals, EXPRKIND_QUAL);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
- preprocess_qual_conditions(parse, j->larg);
- preprocess_qual_conditions(parse, j->rarg);
+ preprocess_qual_conditions(root, j->larg);
+ preprocess_qual_conditions(root, j->rarg);
- j->quals = preprocess_expression(parse, j->quals, EXPRKIND_QUAL);
+ j->quals = preprocess_expression(root, 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.
+ * 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. Also, for both UPDATE
+ * and DELETE, the executor needs the Append plan node at the top, else it
+ * can't keep track of which table is the current target table. 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.
*
* Returns a query plan.
- *--------------------
*/
static Plan *
-inheritance_planner(Query *parse, List *inheritlist)
+inheritance_planner(PlannerInfo *root)
{
+ Query *parse = root->parse;
int parentRTindex = parse->resultRelation;
- Oid parentOID = getrelid(parentRTindex, parse->rtable);
- int mainrtlength = length(parse->rtable);
List *subplans = NIL;
+ List *resultRelations = NIL;
+ List *returningLists = NIL;
+ List *rtable = NIL;
List *tlist = NIL;
- List *l;
+ PlannerInfo subroot;
+ ListCell *l;
- foreach(l, inheritlist)
+ foreach(l, root->append_rel_list)
{
- int childRTindex = lfirsti(l);
- Oid childOID = getrelid(childRTindex, parse->rtable);
- int subrtlength;
- Query *subquery;
+ AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
Plan *subplan;
- /* Generate modified query with this rel as target */
- subquery = (Query *) adjust_inherited_attrs((Node *) parse,
- parentRTindex, parentOID,
- childRTindex, childOID);
+ /* append_rel_list contains all append rels; ignore others */
+ if (appinfo->parent_relid != parentRTindex)
+ continue;
+
+ /*
+ * Generate modified query with this rel as target. We have to be
+ * prepared to translate varnos in in_info_list as well as in the
+ * Query proper.
+ */
+ memcpy(&subroot, root, sizeof(PlannerInfo));
+ subroot.parse = (Query *)
+ adjust_appendrel_attrs((Node *) parse,
+ appinfo);
+ subroot.in_info_list = (List *)
+ adjust_appendrel_attrs((Node *) root->in_info_list,
+ appinfo);
+ subroot.init_plans = NIL;
+ /* There shouldn't be any OJ info to translate, as yet */
+ Assert(subroot.oj_info_list == NIL);
+
/* Generate plan */
- subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
- subplans = lappend(subplans, subplan);
+ subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
/*
- * 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.
+ * If this child rel was excluded by constraint exclusion, exclude it
+ * from the plan.
*/
- subrtlength = length(subquery->rtable);
- if (subrtlength > mainrtlength)
+ if (is_dummy_plan(subplan))
+ continue;
+
+ /* Save rtable and tlist from first rel for use below */
+ if (subplans == NIL)
{
- List *subrt = subquery->rtable;
+ rtable = subroot.parse->rtable;
+ tlist = subplan->targetlist;
+ }
- while (mainrtlength-- > 0) /* wish we had nthcdr() */
- subrt = lnext(subrt);
- parse->rtable = nconc(parse->rtable, subrt);
- mainrtlength = subrtlength;
+ subplans = lappend(subplans, subplan);
+
+ /* Make sure any initplans from this rel get into the outer list */
+ root->init_plans = list_concat(root->init_plans, subroot.init_plans);
+
+ /* Build target-relations list for the executor */
+ resultRelations = lappend_int(resultRelations, appinfo->child_relid);
+
+ /* Build list of per-relation RETURNING targetlists */
+ if (parse->returningList)
+ {
+ Assert(list_length(subroot.returningLists) == 1);
+ returningLists = list_concat(returningLists,
+ subroot.returningLists);
}
- /* 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;
+ root->resultRelations = resultRelations;
+ root->returningLists = returningLists;
/* Mark result as unordered (probably unnecessary) */
- parse->query_pathkeys = NIL;
+ root->query_pathkeys = NIL;
+
+ /*
+ * If we managed to exclude every child rel, return a dummy plan
+ */
+ if (subplans == NIL)
+ {
+ root->resultRelations = list_make1_int(parentRTindex);
+ /* although dummy, it must have a valid tlist for executor */
+ tlist = preprocess_targetlist(root, parse->targetList);
+ return (Plan *) make_result(root,
+ tlist,
+ (Node *) list_make1(makeBoolConst(false,
+ false)),
+ NULL);
+ }
+
+ /*
+ * Planning might have modified the rangetable, due to changes of the
+ * Query structures inside subquery RTEs. We have to ensure that this
+ * gets propagated back to the master copy. But can't do this until we
+ * are done planning, because all the calls to grouping_planner need
+ * virgin sub-Queries to work from. (We are effectively assuming that
+ * sub-Queries will get planned identically each time, or at least that
+ * the impacts on their rangetables will be the same each time.)
+ *
+ * XXX should clean this up someday
+ */
+ parse->rtable = rtable;
+
+ /* Suppress Append if there's only one surviving child rel */
+ if (list_length(subplans) == 1)
+ return (Plan *) linitial(subplans);
return (Plan *) make_append(subplans, true, tlist);
}
* 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:
* tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
* expected to be retrieved (ie, a LIMIT specification)
*
- * Returns a query plan. Also, parse->query_pathkeys is returned as the
+ * Returns a query plan. Also, root->query_pathkeys is returned as the
* actual output ordering of the plan (in pathkey format).
*--------------------
*/
static Plan *
-grouping_planner(Query *parse, double tuple_fraction)
+grouping_planner(PlannerInfo *root, double tuple_fraction)
{
+ Query *parse = root->parse;
List *tlist = parse->targetList;
+ int64 offset_est = 0;
+ int64 count_est = 0;
+ double limit_tuples = -1.0;
Plan *result_plan;
List *current_pathkeys;
List *sort_pathkeys;
+ double dNumGroups = 0;
+
+ /* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
+ if (parse->limitCount || parse->limitOffset)
+ {
+ tuple_fraction = preprocess_limit(root, tuple_fraction,
+ &offset_est, &count_est);
+
+ /*
+ * If we have a known LIMIT, and don't have an unknown OFFSET, we can
+ * estimate the effects of using a bounded sort.
+ */
+ if (count_est > 0 && offset_est >= 0)
+ limit_tuples = (double) count_est + (double) offset_est;
+ }
if (parse->setOperations)
{
- List *set_sortclauses;
+ List *set_sortclauses;
+
+ /*
+ * If there's a top-level ORDER BY, assume we have to fetch all the
+ * tuples. This might seem too simplistic given all the hackery below
+ * to possibly avoid the sort ... but a nonzero tuple_fraction is only
+ * of use to plan_set_operations() when the setop is UNION ALL, and
+ * the result of UNION ALL is always unsorted.
+ */
+ if (parse->sortClause)
+ tuple_fraction = 0.0;
/*
- * Construct the plan for set operations. The result will not
- * need any work except perhaps a top-level sort and/or LIMIT.
+ * Construct the plan for set operations. The result will not need
+ * any work except perhaps a top-level sort and/or LIMIT.
*/
- result_plan = plan_set_operations(parse,
+ result_plan = plan_set_operations(root, tuple_fraction,
&set_sortclauses);
/*
- * 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...
+ * 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...
*/
- current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
- result_plan->targetlist);
- current_pathkeys = canonicalize_pathkeys(parse, current_pathkeys);
+ current_pathkeys = make_pathkeys_for_sortclauses(root,
+ set_sortclauses,
+ result_plan->targetlist,
+ true);
/*
- * 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.
+ * 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.
*/
Assert(parse->commandType == CMD_SELECT);
tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
/*
- * Can't handle FOR UPDATE here (parser should have checked
+ * Can't handle FOR UPDATE/SHARE 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")));
+ errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
/*
* Calculate pathkeys that represent result ordering requirements
*/
- sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
- tlist);
- sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
+ sort_pathkeys = make_pathkeys_for_sortclauses(root,
+ parse->sortClause,
+ tlist,
+ true);
}
else
{
List *sub_tlist;
List *group_pathkeys;
AttrNumber *groupColIdx = NULL;
+ Oid *groupOperators = NULL;
bool need_tlist_eval = true;
QualCost tlist_cost;
- double sub_tuple_fraction;
Path *cheapest_path;
Path *sorted_path;
- double dNumGroups = 0;
+ Path *best_path;
long numGroups = 0;
- int numAggs = 0;
- int numGroupCols = length(parse->groupClause);
+ AggClauseCounts agg_counts;
+ 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->commandType,
- parse->resultRelation,
- parse->rtable);
-
- /*
- * 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->rowMarks)
- {
- List *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")));
+ MemSet(&agg_counts, 0, sizeof(AggClauseCounts));
- foreach(l, parse->rowMarks)
- {
- Index rti = lfirsti(l);
- char *resname;
- Resdom *resdom;
- Var *var;
- TargetEntry *ctid;
-
- resname = (char *) palloc(32);
- snprintf(resname, 32, "ctid%u", rti);
- resdom = makeResdom(length(tlist) + 1,
- TIDOID,
- -1,
- resname,
- true);
-
- var = makeVar(rti,
- SelfItemPointerAttributeNumber,
- TIDOID,
- -1,
- 0);
-
- ctid = makeTargetEntry(resdom, (Expr *) var);
- tlist = lappend(tlist, ctid);
- }
- }
+ /* Preprocess targetlist */
+ tlist = preprocess_targetlist(root, tlist);
/*
- * Generate appropriate target list for subplan; may be different
- * from tlist if grouping or aggregation is needed.
+ * Generate appropriate target list for subplan; may be different from
+ * tlist if grouping or aggregation is needed.
*/
- sub_tlist = make_subplanTargetList(parse, tlist,
- &groupColIdx, &need_tlist_eval);
+ sub_tlist = make_subplanTargetList(root, tlist,
+ &groupColIdx, &need_tlist_eval);
/*
- * Calculate pathkeys that represent grouping/ordering
- * requirements
+ * Calculate pathkeys that represent grouping/ordering requirements.
+ * Stash them in PlannerInfo so that query_planner can canonicalize
+ * them after EquivalenceClasses have been formed.
*/
- group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
- tlist);
- sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
- tlist);
+ root->group_pathkeys =
+ make_pathkeys_for_sortclauses(root,
+ parse->groupClause,
+ tlist,
+ false);
+ root->sort_pathkeys =
+ make_pathkeys_for_sortclauses(root,
+ parse->sortClause,
+ tlist,
+ false);
/*
* 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
+ * 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);
+ {
+ count_agg_clauses((Node *) tlist, &agg_counts);
+ count_agg_clauses(parse->havingQual, &agg_counts);
+ }
/*
* Figure out whether we need a sorted result from query_planner.
*
- * If we have a GROUP BY clause, then we want a result sorted
- * properly for grouping. Otherwise, if there is an ORDER BY
- * clause, we want to sort by the ORDER BY clause. (Note: if we
- * have both, and ORDER BY is a superset of GROUP BY, it would be
- * tempting to request sort by ORDER BY --- but that might just
- * leave us failing to exploit an available sort order at all.
- * Needs more thought...)
+ * If we have a GROUP BY clause, then we want a result sorted properly
+ * for grouping. Otherwise, if there is an ORDER BY clause, we want
+ * to sort by the ORDER BY clause. (Note: if we have both, and ORDER
+ * BY is a superset of GROUP BY, it would be tempting to request sort
+ * by ORDER BY --- but that might just leave us failing to exploit an
+ * available sort order at all. Needs more thought...)
*/
if (parse->groupClause)
- parse->query_pathkeys = group_pathkeys;
+ root->query_pathkeys = root->group_pathkeys;
else if (parse->sortClause)
- parse->query_pathkeys = sort_pathkeys;
+ root->query_pathkeys = root->sort_pathkeys;
else
- parse->query_pathkeys = NIL;
+ root->query_pathkeys = NIL;
/*
- * 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.
+ * Generate the best unsorted and presorted paths for this Query (but
+ * note there may not be any presorted path). query_planner will also
+ * estimate the number of groups in the query, and canonicalize all
+ * the pathkeys.
*/
- if (parse->limitCount != NULL)
- {
- /*
- * 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.
- */
- double limit_fraction = 0.0;
+ query_planner(root, sub_tlist, tuple_fraction, limit_tuples,
+ &cheapest_path, &sorted_path, &dNumGroups);
- 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)
- {
- limit_fraction = (double) count;
- /* We must also consider the OFFSET, if present */
- 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
- {
- /* 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
- {
- /* no info from caller, just use limit */
- tuple_fraction = limit_fraction;
- }
- }
- }
+ group_pathkeys = root->group_pathkeys;
+ sort_pathkeys = root->sort_pathkeys;
/*
- * With grouping or aggregation, the tuple fraction to pass to
- * query_planner() may be different from what it is at top level.
+ * If grouping, extract the grouping operators and decide whether we
+ * want to use hashed grouping.
*/
- 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
- * group, so we can't translate an output LIMIT count into an
- * input count. For lack of a better idea, assume 25% of the
- * input data will be processed if there is any output limit.
- * However, if the caller gave us a fraction rather than an
- * absolute count, we can keep using that fraction (which
- * amounts to assuming that all the groups are about the same
- * size).
- */
- 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. (We have not yet canonicalized the pathkeys,
- * so must use the slower noncanonical comparison method.)
- */
- if (parse->groupClause && parse->sortClause &&
- !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.
- */
- 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 (sub_tuple_fraction >= 1.0)
- sub_tuple_fraction = 0.25;
+ groupOperators = extract_grouping_ops(parse->groupClause);
+ use_hashed_grouping =
+ choose_hashed_grouping(root, tuple_fraction, limit_tuples,
+ cheapest_path, sorted_path,
+ groupOperators, dNumGroups,
+ &agg_counts);
+
+ /* Also convert # groups to long int --- but 'ware overflow! */
+ numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
}
/*
- * 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);
-
- /*
- * We couldn't canonicalize group_pathkeys and sort_pathkeys
- * before running query_planner(), so do it now.
+ * Select the best path. 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.
*/
- group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
- sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
+ if (use_hashed_grouping || !sorted_path)
+ best_path = cheapest_path;
+ else
+ best_path = sorted_path;
/*
- * Consider whether we might want to use hashed grouping.
+ * Check to see if it's possible to optimize MIN/MAX aggregates. If
+ * so, we will forget all the work we did so far to choose a "regular"
+ * path ... but we had to do it anyway to be able to tell which way is
+ * cheaper.
*/
- if (parse->groupClause)
+ result_plan = optimize_minmax_aggregates(root,
+ tlist,
+ best_path);
+ if (result_plan != NULL)
{
- List *groupExprs;
- double cheapest_path_rows;
- int cheapest_path_width;
-
/*
- * 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;
+ * optimize_minmax_aggregates generated the full plan, with the
+ * right tlist, and it has no sort order.
*/
- 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 */
- }
-
+ current_pathkeys = NIL;
+ }
+ else
+ {
/*
- * Always estimate the number of groups. We can't do this
- * until after running query_planner(), either.
+ * Normal case --- create a plan according to query_planner's
+ * results.
*/
- 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);
+ result_plan = create_plan(root, best_path);
+ current_pathkeys = best_path->pathkeys;
/*
- * 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.)
+ * 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 (!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
+ if (need_tlist_eval)
{
/*
- * 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.
+ * If the top-level plan node is one that cannot do expression
+ * evaluation, we must insert a Result node to project the
+ * desired tlist.
*/
- int hashentrysize = cheapest_path_width + 64 + numAggs * 100;
-
- if (hashentrysize * dNumGroups <= work_mem * 1024L)
+ if (!is_projection_capable_plan(result_plan))
+ {
+ result_plan = (Plan *) make_result(root,
+ sub_tlist,
+ NULL,
+ result_plan);
+ }
+ else
{
/*
- * 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.
+ * Otherwise, just replace the subplan's flat tlist with
+ * the desired tlist.
*/
- 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;
- }
+ result_plan->targetlist = sub_tlist;
}
- }
- }
- /*
- * 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.
- */
- 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;
- }
-
- /*
- * 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 (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);
+ /*
+ * 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, root);
+ result_plan->startup_cost += tlist_cost.startup;
+ result_plan->total_cost += tlist_cost.startup +
+ tlist_cost.per_tuple * result_plan->plan_rows;
}
else
{
/*
- * Otherwise, just replace the subplan's flat tlist with
- * the desired 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.
*/
- result_plan->targetlist = sub_tlist;
+ locate_grouping_columns(root, tlist, result_plan->targetlist,
+ groupColIdx);
}
/*
- * Also, account for the cost of evaluation of the sub_tlist.
+ * Insert AGG or GROUP node if needed, plus an explicit sort step
+ * if necessary.
*
- * 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
- {
- /*
- * 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.
+ * HAVING clause, if any, becomes qual of the Agg or Group node.
*/
- locate_grouping_columns(parse, tlist, result_plan->targetlist,
- groupColIdx);
- }
+ if (use_hashed_grouping)
+ {
+ /* Hashed aggregate plan --- no sort needed */
+ result_plan = (Plan *) make_agg(root,
+ tlist,
+ (List *) parse->havingQual,
+ AGG_HASHED,
+ numGroupCols,
+ groupColIdx,
+ groupOperators,
+ numGroups,
+ agg_counts.numAggs,
+ result_plan);
+ /* Hashed aggregation produces randomly-ordered results */
+ current_pathkeys = NIL;
+ }
+ else if (parse->hasAggs)
+ {
+ /* Plain aggregate plan --- sort if needed */
+ AggStrategy aggstrategy;
- /*
- * 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 (use_hashed_grouping)
- {
- /* 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 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(root,
+ parse->groupClause,
+ groupColIdx,
+ result_plan);
+ current_pathkeys = group_pathkeys;
+ }
+ aggstrategy = AGG_SORTED;
- if (parse->groupClause)
- {
- if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
+ /*
+ * The AGG node will not change the sort ordering of its
+ * groups, so current_pathkeys describes the result too.
+ */
+ }
+ else
{
- result_plan = (Plan *)
- make_sort_from_groupcols(parse,
- parse->groupClause,
- groupColIdx,
- result_plan);
- current_pathkeys = group_pathkeys;
+ aggstrategy = AGG_PLAIN;
+ /* Result will be only one row anyway; no sort order */
+ current_pathkeys = NIL;
}
- aggstrategy = AGG_SORTED;
- /*
- * The AGG node will not change the sort ordering of its
- * groups, so current_pathkeys describes the result too.
- */
+ result_plan = (Plan *) make_agg(root,
+ tlist,
+ (List *) parse->havingQual,
+ aggstrategy,
+ numGroupCols,
+ groupColIdx,
+ groupOperators,
+ numGroups,
+ agg_counts.numAggs,
+ result_plan);
}
- 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
- {
- /*
- * If there are no Aggs, we shouldn't have any HAVING qual
- * anymore
- */
- Assert(parse->havingQual == NULL);
-
- /*
- * If we have a GROUP BY clause, insert a group node (plus the
- * appropriate sort node, if necessary).
- */
- if (parse->groupClause)
+ else if (parse->groupClause)
{
/*
- * Add an explicit sort if we couldn't make the path come
- * out the way the GROUP node needs it.
+ * GROUP BY without aggregation, so insert a group node (plus
+ * the appropriate sort node, if necessary).
+ *
+ * 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,
+ make_sort_from_groupcols(root,
parse->groupClause,
groupColIdx,
result_plan);
current_pathkeys = group_pathkeys;
}
- result_plan = (Plan *) make_group(parse,
+ result_plan = (Plan *) make_group(root,
tlist,
+ (List *) parse->havingQual,
numGroupCols,
groupColIdx,
+ groupOperators,
dNumGroups,
result_plan);
/* The Group node won't change sort ordering */
}
- }
+ else if (root->hasHavingQual)
+ {
+ /*
+ * No aggregates, and no GROUP BY, but we have a HAVING qual.
+ * This is a degenerate case in which we are supposed to emit
+ * either 0 or 1 row depending on whether HAVING succeeds.
+ * Furthermore, there cannot be any variables in either HAVING
+ * or the targetlist, so we actually do not need the FROM
+ * table at all! We can just throw away the plan-so-far and
+ * generate a Result node. This is a sufficiently unusual
+ * corner case that it's not worth contorting the structure of
+ * this routine to avoid having to generate the plan in the
+ * first place.
+ */
+ result_plan = (Plan *) make_result(root,
+ tlist,
+ parse->havingQual,
+ NULL);
+ }
+ } /* end of non-minmax-aggregate case */
} /* end of if (setOperations) */
/*
- * If we were not able to make the plan come out in the right order,
- * add an explicit sort step.
+ * If we were not able to make the plan come out in the right order, add
+ * an explicit sort step.
*/
if (parse->sortClause)
{
if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
{
- result_plan = (Plan *)
- make_sort_from_sortclauses(parse,
- parse->sortClause,
- result_plan);
+ result_plan = (Plan *) make_sort_from_pathkeys(root,
+ result_plan,
+ sort_pathkeys,
+ limit_tuples);
current_pathkeys = sort_pathkeys;
}
}
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 there was grouping or aggregation, leave plan_rows as-is (ie,
+ * assume the result was already mostly unique). If not, use the
+ * number of distinct-groups calculated by query_planner.
*/
- 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);
- }
+ if (!parse->groupClause && !root->hasHavingQual && !parse->hasAggs)
+ result_plan->plan_rows = dNumGroups;
}
/*
* Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
*/
- if (parse->limitOffset || parse->limitCount)
+ if (parse->limitCount || parse->limitOffset)
{
result_plan = (Plan *) make_limit(result_plan,
parse->limitOffset,
- parse->limitCount);
+ parse->limitCount,
+ offset_est,
+ count_est);
}
/*
- * Return the actual output ordering in query_pathkeys for possible
- * use by an outer query level.
+ * Deal with the RETURNING clause if any. It's convenient to pass the
+ * returningList through setrefs.c now rather than at top level (if we
+ * waited, handling inherited UPDATE/DELETE would be much harder).
*/
- parse->query_pathkeys = current_pathkeys;
+ if (parse->returningList)
+ {
+ List *rlist;
+
+ Assert(parse->resultRelation);
+ rlist = set_returning_clause_references(root->glob,
+ parse->returningList,
+ result_plan,
+ parse->resultRelation);
+ root->returningLists = list_make1(rlist);
+ }
+ else
+ root->returningLists = NIL;
+
+ /* Compute result-relations list if needed */
+ if (parse->resultRelation)
+ root->resultRelations = list_make1_int(parse->resultRelation);
+ else
+ root->resultRelations = NIL;
+
+ /*
+ * Return the actual output ordering in query_pathkeys for possible use by
+ * an outer query level.
+ */
+ root->query_pathkeys = current_pathkeys;
return result_plan;
}
/*
- * hash_safe_grouping - are grouping operators hashable?
+ * Detect whether a plan node is a "dummy" plan created when a relation
+ * is deemed not to need scanning due to constraint exclusion.
*
- * We assume hashed aggregation will work if the datatype's equality operator
- * is marked hashjoinable.
+ * Currently, such dummy plans are Result nodes with constant FALSE
+ * filter quals.
*/
static bool
-hash_safe_grouping(Query *parse)
+is_dummy_plan(Plan *plan)
{
- List *gl;
+ if (IsA(plan, Result))
+ {
+ List *rcqual = (List *) ((Result *) plan)->resconstantqual;
- foreach(gl, parse->groupClause)
+ if (list_length(rcqual) == 1)
+ {
+ Const *constqual = (Const *) linitial(rcqual);
+
+ if (constqual && IsA(constqual, Const))
+ {
+ if (!constqual->constisnull &&
+ !DatumGetBool(constqual->constvalue))
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+/*
+ * preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
+ *
+ * We try to estimate the values of the LIMIT/OFFSET clauses, and pass the
+ * results back in *count_est and *offset_est. These variables are set to
+ * 0 if the corresponding clause is not present, and -1 if it's present
+ * but we couldn't estimate the value for it. (The "0" convention is OK
+ * for OFFSET but a little bit bogus for LIMIT: effectively we estimate
+ * LIMIT 0 as though it were LIMIT 1. But this is in line with the planner's
+ * usual practice of never estimating less than one row.) These values will
+ * be passed to make_limit, which see if you change this code.
+ *
+ * The return value is the suitably adjusted tuple_fraction to use for
+ * planning the query. This adjustment is not overridable, since it reflects
+ * plan actions that grouping_planner() will certainly take, not assumptions
+ * about context.
+ */
+static double
+preprocess_limit(PlannerInfo *root, double tuple_fraction,
+ int64 *offset_est, int64 *count_est)
+{
+ Query *parse = root->parse;
+ Node *est;
+ double limit_fraction;
+
+ /* Should not be called unless LIMIT or OFFSET */
+ Assert(parse->limitCount || parse->limitOffset);
+
+ /*
+ * Try to obtain the clause values. We use estimate_expression_value
+ * primarily because it can sometimes do something useful with Params.
+ */
+ if (parse->limitCount)
{
- GroupClause *grpcl = (GroupClause *) lfirst(gl);
- TargetEntry *tle = get_sortgroupclause_tle(grpcl, parse->targetList);
- Operator optup;
- bool oprcanhash;
+ est = estimate_expression_value(root, parse->limitCount);
+ if (est && IsA(est, Const))
+ {
+ if (((Const *) est)->constisnull)
+ {
+ /* NULL indicates LIMIT ALL, ie, no limit */
+ *count_est = 0; /* treat as not present */
+ }
+ else
+ {
+ *count_est = DatumGetInt64(((Const *) est)->constvalue);
+ if (*count_est <= 0)
+ *count_est = 1; /* force to at least 1 */
+ }
+ }
+ else
+ *count_est = -1; /* can't estimate */
+ }
+ else
+ *count_est = 0; /* not present */
- optup = equality_oper(tle->resdom->restype, true);
- if (!optup)
- return false;
- oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
- ReleaseSysCache(optup);
- if (!oprcanhash)
+ if (parse->limitOffset)
+ {
+ est = estimate_expression_value(root, parse->limitOffset);
+ if (est && IsA(est, Const))
+ {
+ if (((Const *) est)->constisnull)
+ {
+ /* Treat NULL as no offset; the executor will too */
+ *offset_est = 0; /* treat as not present */
+ }
+ else
+ {
+ *offset_est = DatumGetInt64(((Const *) est)->constvalue);
+ if (*offset_est < 0)
+ *offset_est = 0; /* less than 0 is same as 0 */
+ }
+ }
+ else
+ *offset_est = -1; /* can't estimate */
+ }
+ else
+ *offset_est = 0; /* not present */
+
+ if (*count_est != 0)
+ {
+ /*
+ * A LIMIT clause limits the absolute number of tuples returned.
+ * However, if it's not a constant LIMIT then we have to guess; for
+ * lack of a better idea, assume 10% of the plan's result is wanted.
+ */
+ if (*count_est < 0 || *offset_est < 0)
+ {
+ /* LIMIT or OFFSET is an expression ... punt ... */
+ limit_fraction = 0.10;
+ }
+ else
+ {
+ /* LIMIT (plus OFFSET, if any) is max number of tuples needed */
+ limit_fraction = (double) *count_est + (double) *offset_est;
+ }
+
+ /*
+ * If we have absolute limits from both caller and LIMIT, use the
+ * smaller value; likewise if they are both fractional. If one is
+ * fractional and the other absolute, we can't easily determine which
+ * is smaller, but we use the heuristic that the absolute will usually
+ * be smaller.
+ */
+ if (tuple_fraction >= 1.0)
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* both absolute */
+ tuple_fraction = Min(tuple_fraction, limit_fraction);
+ }
+ else
+ {
+ /* caller absolute, limit fractional; use caller's value */
+ }
+ }
+ else if (tuple_fraction > 0.0)
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* caller fractional, limit absolute; use limit */
+ tuple_fraction = limit_fraction;
+ }
+ else
+ {
+ /* both fractional */
+ tuple_fraction = Min(tuple_fraction, limit_fraction);
+ }
+ }
+ else
+ {
+ /* no info from caller, just use limit */
+ tuple_fraction = limit_fraction;
+ }
+ }
+ else if (*offset_est != 0 && tuple_fraction > 0.0)
+ {
+ /*
+ * We have an OFFSET but no LIMIT. This acts entirely differently
+ * from the LIMIT case: here, we need to increase rather than decrease
+ * the caller's tuple_fraction, because the OFFSET acts to cause more
+ * tuples to be fetched instead of fewer. This only matters if we got
+ * a tuple_fraction > 0, however.
+ *
+ * As above, use 10% if OFFSET is present but unestimatable.
+ */
+ if (*offset_est < 0)
+ limit_fraction = 0.10;
+ else
+ limit_fraction = (double) *offset_est;
+
+ /*
+ * If we have absolute counts from both caller and OFFSET, add them
+ * together; likewise if they are both fractional. If one is
+ * fractional and the other absolute, we want to take the larger, and
+ * we heuristically assume that's the fractional one.
+ */
+ if (tuple_fraction >= 1.0)
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* both absolute, so add them together */
+ tuple_fraction += limit_fraction;
+ }
+ else
+ {
+ /* caller absolute, limit fractional; use limit */
+ tuple_fraction = limit_fraction;
+ }
+ }
+ else
+ {
+ if (limit_fraction >= 1.0)
+ {
+ /* caller fractional, limit absolute; use caller's value */
+ }
+ else
+ {
+ /* both fractional, so add them together */
+ tuple_fraction += limit_fraction;
+ if (tuple_fraction >= 1.0)
+ tuple_fraction = 0.0; /* assume fetch all */
+ }
+ }
+ }
+
+ return tuple_fraction;
+}
+
+/*
+ * extract_grouping_ops - make an array of the equality operator OIDs
+ * for the GROUP BY clause
+ */
+static Oid *
+extract_grouping_ops(List *groupClause)
+{
+ int numCols = list_length(groupClause);
+ int colno = 0;
+ Oid *groupOperators;
+ ListCell *glitem;
+
+ groupOperators = (Oid *) palloc(sizeof(Oid) * numCols);
+
+ foreach(glitem, groupClause)
+ {
+ GroupClause *groupcl = (GroupClause *) lfirst(glitem);
+
+ groupOperators[colno] = get_equality_op_for_ordering_op(groupcl->sortop);
+ if (!OidIsValid(groupOperators[colno])) /* shouldn't happen */
+ elog(ERROR, "could not find equality operator for ordering operator %u",
+ groupcl->sortop);
+ colno++;
+ }
+
+ return groupOperators;
+}
+
+/*
+ * choose_hashed_grouping - should we use hashed grouping?
+ */
+static bool
+choose_hashed_grouping(PlannerInfo *root,
+ double tuple_fraction, double limit_tuples,
+ Path *cheapest_path, Path *sorted_path,
+ Oid *groupOperators, double dNumGroups,
+ AggClauseCounts *agg_counts)
+{
+ int numGroupCols = list_length(root->parse->groupClause);
+ double cheapest_path_rows;
+ int cheapest_path_width;
+ Size hashentrysize;
+ List *current_pathkeys;
+ Path hashed_p;
+ Path sorted_p;
+ int i;
+
+ /*
+ * Check can't-do-it conditions, including whether the grouping operators
+ * are hashjoinable. (We assume hashing is OK if they are marked
+ * oprcanhash. If there isn't actually a supporting hash function, the
+ * executor will complain at runtime.)
+ *
+ * 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)
+ return false;
+ if (agg_counts->numDistinctAggs != 0)
+ return false;
+ for (i = 0; i < numGroupCols; i++)
+ {
+ if (!op_hashjoinable(groupOperators[i]))
return false;
}
- return true;
+
+ /*
+ * Don't do it if it doesn't look like the hashtable will fit into
+ * work_mem.
+ *
+ * Beware here 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 */
+ }
+
+ /* Estimate per-hash-entry space at tuple width... */
+ hashentrysize = MAXALIGN(cheapest_path_width) + MAXALIGN(sizeof(MinimalTupleData));
+ /* plus space for pass-by-ref transition values... */
+ hashentrysize += agg_counts->transitionSpace;
+ /* plus the per-hash-entry overhead */
+ hashentrysize += hash_agg_entry_size(agg_counts->numAggs);
+
+ if (hashentrysize * dNumGroups > work_mem * 1024L)
+ return false;
+
+ /*
+ * See if 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.
+ *
+ * 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.
+ */
+ cost_agg(&hashed_p, root, AGG_HASHED, agg_counts->numAggs,
+ numGroupCols, dNumGroups,
+ cheapest_path->startup_cost, cheapest_path->total_cost,
+ cheapest_path_rows);
+ /* Result of hashed agg is always unsorted */
+ if (root->sort_pathkeys)
+ cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
+ dNumGroups, cheapest_path_width, limit_tuples);
+
+ 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(root->group_pathkeys, current_pathkeys))
+ {
+ cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
+ cheapest_path_rows, cheapest_path_width, -1.0);
+ current_pathkeys = root->group_pathkeys;
+ }
+
+ if (root->parse->hasAggs)
+ cost_agg(&sorted_p, root, AGG_SORTED, agg_counts->numAggs,
+ numGroupCols, dNumGroups,
+ sorted_p.startup_cost, sorted_p.total_cost,
+ cheapest_path_rows);
+ else
+ cost_group(&sorted_p, root, numGroupCols, dNumGroups,
+ sorted_p.startup_cost, sorted_p.total_cost,
+ cheapest_path_rows);
+ /* The Agg or Group node will preserve ordering */
+ if (root->sort_pathkeys &&
+ !pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
+ cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost,
+ dNumGroups, cheapest_path_width, limit_tuples);
+
+ /*
+ * 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 */
+ return true;
+ }
+ return false;
}
/*---------------
* make_subplanTargetList
* Generate appropriate target list when grouping is required.
*
- * When grouping_planner inserts Aggregate or Group plan nodes above
- * the result of query_planner, we typically want to pass a different
+ * When grouping_planner inserts Aggregate, Group, or Result 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.
*
* The initial target list passed from the parser already contains entries
* for all ORDER BY and GROUP BY expressions, but it will not have entries
* for variables used only in HAVING clauses; so we need to add those
- * variables to the subplan target list. Also, if we are doing either
- * grouping or aggregation, we flatten all expressions except GROUP BY items
- * into their component variables; the other expressions will be computed by
- * the inserted nodes rather than by the subplan. For example,
- * given a query like
+ * variables to the subplan target list. Also, we flatten all expressions
+ * except GROUP BY items into their component variables; the other expressions
+ * will be computed by the inserted nodes rather than by the subplan.
+ * For example, given a query like
* SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
* we want to pass this targetlist to the subplan:
* a,b,c,d,a+b
* 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.)
+ * fix_upper_expr() 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.
*---------------
*/
static List *
-make_subplanTargetList(Query *parse,
+make_subplanTargetList(PlannerInfo *root,
List *tlist,
AttrNumber **groupColIdx,
bool *need_tlist_eval)
{
+ Query *parse = root->parse;
List *sub_tlist;
List *extravars;
int numCols;
*groupColIdx = NULL;
/*
- * If we're not grouping or aggregating, nothing to do here;
+ * If we're not grouping or aggregating, there's nothing to do here;
* query_planner should receive the unmodified target list.
*/
- if (!parse->hasAggs && !parse->groupClause)
+ if (!parse->hasAggs && !parse->groupClause && !root->hasHavingQual)
{
*need_tlist_eval = true;
return tlist;
/*
* Otherwise, start with a "flattened" tlist (having just the vars
- * mentioned in the targetlist and HAVING qual --- but not upper-
- * level Vars; they will be replaced by Params later on).
+ * mentioned in the targetlist and HAVING qual --- but not upper- level
+ * Vars; they will be replaced by Params later on).
*/
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
- * (GROUP BY items that are simple Vars should be in the list
- * already), and make an array showing where the group columns are in
- * the sub_tlist.
+ * (GROUP BY items that are simple Vars should be in the list 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;
GroupClause *grpcl = (GroupClause *) lfirst(gl);
Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
TargetEntry *te = NULL;
- List *sl;
+ ListCell *sl;
/* Find or make a matching sub_tlist entry */
foreach(sl, sub_tlist)
}
if (!sl)
{
- te = makeTargetEntry(makeResdom(length(sub_tlist) + 1,
- exprType(groupexpr),
- exprTypmod(groupexpr),
- NULL,
- false),
- (Expr *) groupexpr);
+ te = makeTargetEntry((Expr *) groupexpr,
+ list_length(sub_tlist) + 1,
+ NULL,
+ false);
sub_tlist = lappend(sub_tlist, te);
*need_tlist_eval = true; /* it's not flat anymore */
}
/* and save its resno */
- grpColIdx[keyno++] = te->resdom->resno;
+ grpColIdx[keyno++] = te->resno;
}
}
* by that routine and re-locate the grouping vars in the real sub_tlist.
*/
static void
-locate_grouping_columns(Query *parse,
+locate_grouping_columns(PlannerInfo *root,
List *tlist,
List *sub_tlist,
AttrNumber *groupColIdx)
{
int keyno = 0;
- List *gl;
+ ListCell *gl;
/*
* No work unless grouping.
*/
- if (!parse->groupClause)
+ if (!root->parse->groupClause)
{
Assert(groupColIdx == NULL);
return;
}
Assert(groupColIdx != NULL);
- foreach(gl, parse->groupClause)
+ foreach(gl, root->parse->groupClause)
{
GroupClause *grpcl = (GroupClause *) lfirst(gl);
Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
TargetEntry *te = NULL;
- List *sl;
+ ListCell *sl;
foreach(sl, sub_tlist)
{
if (!sl)
elog(ERROR, "failed to locate grouping columns");
- groupColIdx[keyno++] = te->resdom->resno;
+ groupColIdx[keyno++] = te->resno;
}
}
static List *
postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
{
- List *l;
+ ListCell *l;
+ ListCell *orig_tlist_item = list_head(orig_tlist);
foreach(l, new_tlist)
{
TargetEntry *orig_tle;
/* ignore resjunk columns in setop result */
- if (new_tle->resdom->resjunk)
+ if (new_tle->resjunk)
continue;
- Assert(orig_tlist != NIL);
- orig_tle = (TargetEntry *) lfirst(orig_tlist);
- orig_tlist = lnext(orig_tlist);
- if (orig_tle->resdom->resjunk) /* should not happen */
+ Assert(orig_tlist_item != NULL);
+ orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
+ orig_tlist_item = lnext(orig_tlist_item);
+ if (orig_tle->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(new_tle->resno == orig_tle->resno);
+ new_tle->ressortgroupref = orig_tle->ressortgroupref;
}
- if (orig_tlist != NIL)
+ if (orig_tlist_item != NULL)
elog(ERROR, "resjunk output columns are not implemented");
return new_tlist;
}
projects / postgresql / blobdiff