* planner.c
* The query optimizer external interface.
*
- * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1996-2005, 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 1.115 2002/03/12 00:51:47 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.184 2005/04/11 23:06:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
+#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/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 "rewrite/rewriteManip.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_TARGET 0
-#define EXPRKIND_WHERE 1
-#define EXPRKIND_HAVING 2
+#define EXPRKIND_QUAL 0
+#define EXPRKIND_TARGET 1
+#define EXPRKIND_RTFUNC 2
+#define EXPRKIND_LIMIT 3
+#define EXPRKIND_ININFO 4
-static Node *pull_up_subqueries(Query *parse, Node *jtnode);
-static bool is_simple_subquery(Query *subquery);
-static void resolvenew_in_jointree(Node *jtnode, int varno, List *subtlist);
-static Node *preprocess_jointree(Query *parse, Node *jtnode);
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 choose_hashed_grouping(Query *parse, double tuple_fraction,
+ Path *cheapest_path, Path *sorted_path,
+ List *sort_pathkeys, List *group_pathkeys,
+ double dNumGroups, AggClauseCounts *agg_counts);
+static bool hash_safe_grouping(Query *parse);
static List *make_subplanTargetList(Query *parse, List *tlist,
- AttrNumber **groupColIdx);
-static Plan *make_groupplan(Query *parse,
- List *group_tlist, bool tuplePerGroup,
- List *groupClause, AttrNumber *grpColIdx,
- bool is_presorted, Plan *subplan);
+ 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_PlannerParamVar;
+ List *save_PlannerParamList;
+ ParamListInfo save_PlannerBoundParamList;
/*
* 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.
+ * 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.
*
* 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
* subquery_planner, not here.
*/
save_PlannerQueryLevel = PlannerQueryLevel;
- save_PlannerParamVar = PlannerParamVar;
+ save_PlannerParamList = PlannerParamList;
+ save_PlannerBoundParamList = PlannerBoundParamList;
/* Initialize state for handling outer-level references and params */
PlannerQueryLevel = 0; /* will be 1 in top-level subquery_planner */
- PlannerParamVar = NIL;
+ PlannerParamList = NIL;
+ PlannerBoundParamList = boundParams;
+
+ /* 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 subqueries) */
- result_plan = subquery_planner(parse, -1.0 /* default case */ );
+ result_plan = subquery_planner(parse, tuple_fraction);
Assert(PlannerQueryLevel == 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))
+ {
+ 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(parse, result_plan);
+ set_plan_references(result_plan, parse->rtable);
/* restore state for outer planner, if any */
PlannerQueryLevel = save_PlannerQueryLevel;
- PlannerParamVar = save_PlannerParamVar;
+ PlannerParamList = save_PlannerParamList;
+ PlannerBoundParamList = save_PlannerBoundParamList;
return result_plan;
}
{
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;
-#ifdef ENABLE_KEY_SET_QUERY
- /* this should go away sometime soon */
- transformKeySetQuery(parse);
-#endif
+ /*
+ * 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);
+ pull_up_subqueries(parse, (Node *) parse->jointree, false);
/*
- * If so, we may have created opportunities to simplify the jointree.
+ * 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->jointree = (FromExpr *)
- preprocess_jointree(parse, (Node *) parse->jointree);
+ 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;
+ }
+ }
+ }
+
+ /*
+ * 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.
+ */
+ parse->hasHavingQual = (parse->havingQual != NULL);
/*
* Do expression preprocessing on targetlist and quals.
preprocess_qual_conditions(parse, (Node *) parse->jointree);
parse->havingQual = preprocess_expression(parse, parse->havingQual,
- EXPRKIND_HAVING);
+ EXPRKIND_QUAL);
- /*
- * Check for ungrouped variables passed to subplans in targetlist and
- * HAVING clause (but not in WHERE or JOIN/ON clauses, since those are
- * evaluated before grouping). We can't do this any earlier because
- * we must use the preprocessed targetlist for comparisons of grouped
- * expressions.
- */
- if (parse->hasSubLinks &&
- (parse->groupClause != NIL || parse->hasAggs))
- check_subplans_for_ungrouped_vars(parse);
+ 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). 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 *. Also note that contain_agg_clause does not
- * recurse into sub-selects, which is exactly what we need here.
+ * 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
+ * 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);
+
/*
* 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_inherted_rtentry(parse, parse->resultRelation, false))
- != NIL)
+ (lst = expand_inherited_rtentry(parse, parse->resultRelation)) != NIL)
plan = inheritance_planner(parse, lst);
else
plan = grouping_planner(parse, tuple_fraction);
/*
* If any subplans were generated, or if we're inside a subplan, build
- * subPlan, extParam and locParam lists 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)
- {
- (void) SS_finalize_plan(plan);
-
- /*
- * At the moment, SS_finalize_plan doesn't handle initPlans and so
- * we assign them to the topmost plan node.
- */
- plan->initPlan = PlannerInitPlan;
- /* Must add the initPlans' extParams to the topmost node's, too */
- foreach(lst, plan->initPlan)
- {
- SubPlan *subplan = (SubPlan *) lfirst(lst);
-
- plan->extParam = set_unioni(plan->extParam,
- subplan->plan->extParam);
- }
- }
+ SS_finalize_plan(plan, parse->rtable);
/* Return to outer subquery context */
PlannerQueryLevel--;
return plan;
}
-/*
- * pull_up_subqueries
- * Look for subqueries in the rangetable that can be pulled up into
- * the parent query. If the subquery has no special features like
- * grouping/aggregation then we can merge it into the parent's jointree.
- *
- * A tricky aspect of this code is that if we pull up a subquery we have
- * to replace Vars that reference the subquery's outputs throughout the
- * parent query, including quals attached to jointree nodes above the one
- * we are currently processing! We handle this by being careful not to
- * change the jointree structure while recursing: no nodes other than
- * subquery RangeTblRef entries will be replaced. Also, we can't turn
- * ResolveNew loose on the whole jointree, because it'll return a mutated
- * copy of the tree; we have to invoke it just on the quals, instead.
- */
-static Node *
-pull_up_subqueries(Query *parse, Node *jtnode)
-{
- if (jtnode == NULL)
- return NULL;
- if (IsA(jtnode, RangeTblRef))
- {
- int varno = ((RangeTblRef *) jtnode)->rtindex;
- RangeTblEntry *rte = rt_fetch(varno, parse->rtable);
- Query *subquery = rte->subquery;
-
- /*
- * Is this a subquery RTE, and if so, is the subquery simple
- * enough to pull up? (If not, do nothing at this node.)
- *
- * Note: even if the subquery itself is simple enough, we can't pull
- * it up if there is a reference to its whole tuple result.
- */
- if (subquery && is_simple_subquery(subquery) &&
- !contain_whole_tuple_var((Node *) parse, varno, 0))
- {
- int rtoffset;
- Node *subjointree;
- List *subtlist;
- List *l;
-
- /*
- * First, recursively pull up the subquery's subqueries, so
- * that this routine's processing is complete for its jointree
- * and rangetable. NB: if the same subquery is referenced
- * from multiple jointree items (which can't happen normally,
- * but might after rule rewriting), then we will invoke this
- * processing multiple times on that subquery. OK because
- * nothing will happen after the first time. We do have to be
- * careful to copy everything we pull up, however, or risk
- * having chunks of structure multiply linked.
- */
- subquery->jointree = (FromExpr *)
- pull_up_subqueries(subquery, (Node *) subquery->jointree);
-
- /*
- * Append the subquery's rangetable to mine (currently, no
- * adjustments will be needed in the subquery's rtable).
- */
- rtoffset = length(parse->rtable);
- parse->rtable = nconc(parse->rtable,
- copyObject(subquery->rtable));
-
- /*
- * Make copies of the subquery's jointree and targetlist with
- * varnos adjusted to match the merged rangetable.
- */
- subjointree = copyObject(subquery->jointree);
- OffsetVarNodes(subjointree, rtoffset, 0);
- subtlist = copyObject(subquery->targetList);
- OffsetVarNodes((Node *) subtlist, rtoffset, 0);
-
- /*
- * Replace all of the top query's references to the subquery's
- * outputs with copies of the adjusted subtlist items, being
- * careful not to replace any of the jointree structure.
- */
- parse->targetList = (List *)
- ResolveNew((Node *) parse->targetList,
- varno, 0, subtlist, CMD_SELECT, 0);
- resolvenew_in_jointree((Node *) parse->jointree, varno, subtlist);
- parse->havingQual =
- ResolveNew(parse->havingQual,
- varno, 0, subtlist, CMD_SELECT, 0);
-
- /*
- * Pull up any FOR UPDATE markers, too.
- */
- foreach(l, subquery->rowMarks)
- {
- int submark = lfirsti(l);
-
- parse->rowMarks = lappendi(parse->rowMarks,
- submark + rtoffset);
- }
-
- /*
- * Miscellaneous housekeeping.
- */
- parse->hasSubLinks |= subquery->hasSubLinks;
- /* subquery won't be pulled up if it hasAggs, so no work there */
-
- /*
- * Return the adjusted subquery jointree to replace the
- * RangeTblRef entry in my jointree.
- */
- return subjointree;
- }
- }
- else if (IsA(jtnode, FromExpr))
- {
- FromExpr *f = (FromExpr *) jtnode;
- List *l;
-
- foreach(l, f->fromlist)
- lfirst(l) = pull_up_subqueries(parse, lfirst(l));
- }
- else if (IsA(jtnode, JoinExpr))
- {
- JoinExpr *j = (JoinExpr *) jtnode;
-
- /*
- * At the moment, we can't pull up subqueries that are inside the
- * nullable side of an outer join, because substituting their
- * target list entries for upper Var references wouldn't do the
- * right thing (the entries wouldn't go to NULL when they're
- * supposed to). Suppressing the pullup is an ugly,
- * performance-losing hack, but I see no alternative for now. Find
- * a better way to handle this when we redesign query trees ---
- * tgl 4/30/01.
- */
- switch (j->jointype)
- {
- case JOIN_INNER:
- j->larg = pull_up_subqueries(parse, j->larg);
- j->rarg = pull_up_subqueries(parse, j->rarg);
- break;
- case JOIN_LEFT:
- j->larg = pull_up_subqueries(parse, j->larg);
- break;
- case JOIN_FULL:
- break;
- case JOIN_RIGHT:
- j->rarg = pull_up_subqueries(parse, j->rarg);
- break;
- case JOIN_UNION:
-
- /*
- * This is where we fail if upper levels of planner
- * haven't rewritten UNION JOIN as an Append ...
- */
- elog(ERROR, "UNION JOIN is not implemented yet");
- break;
- default:
- elog(ERROR, "pull_up_subqueries: unexpected join type %d",
- j->jointype);
- break;
- }
- }
- else
- elog(ERROR, "pull_up_subqueries: unexpected node type %d",
- nodeTag(jtnode));
- return jtnode;
-}
-
-/*
- * is_simple_subquery
- * Check a subquery in the range table to see if it's simple enough
- * to pull up into the parent query.
- */
-static bool
-is_simple_subquery(Query *subquery)
-{
- /*
- * Let's just make sure it's a valid subselect ...
- */
- if (!IsA(subquery, Query) ||
- subquery->commandType != CMD_SELECT ||
- subquery->resultRelation != 0 ||
- subquery->into != NULL ||
- subquery->isPortal)
- elog(ERROR, "is_simple_subquery: subquery is bogus");
-
- /*
- * Can't currently pull up a query with setops. Maybe after querytree
- * redesign...
- */
- if (subquery->setOperations)
- return false;
-
- /*
- * Can't pull up a subquery involving grouping, aggregation, sorting,
- * or limiting.
- */
- if (subquery->hasAggs ||
- subquery->groupClause ||
- subquery->havingQual ||
- subquery->sortClause ||
- subquery->distinctClause ||
- subquery->limitOffset ||
- subquery->limitCount)
- return false;
-
- /*
- * Don't pull up a subquery that has any set-returning functions in
- * its targetlist. Otherwise we might well wind up inserting
- * set-returning functions into places where they mustn't go,
- * such as quals of higher queries.
- */
- if (contain_iter_clause((Node *) subquery->targetList))
- return false;
-
- /*
- * Hack: don't try to pull up a subquery with an empty jointree.
- * query_planner() will correctly generate a Result plan for a
- * jointree that's totally empty, but I don't think the right things
- * happen if an empty FromExpr appears lower down in a jointree. Not
- * worth working hard on this, just to collapse SubqueryScan/Result
- * into Result...
- */
- if (subquery->jointree->fromlist == NIL)
- return false;
-
- return true;
-}
-
-/*
- * Helper routine for pull_up_subqueries: do ResolveNew on every expression
- * in the jointree, without changing the jointree structure itself. Ugly,
- * but there's no other way...
- */
-static void
-resolvenew_in_jointree(Node *jtnode, int varno, List *subtlist)
-{
- if (jtnode == NULL)
- return;
- if (IsA(jtnode, RangeTblRef))
- {
- /* nothing to do here */
- }
- else if (IsA(jtnode, FromExpr))
- {
- FromExpr *f = (FromExpr *) jtnode;
- List *l;
-
- foreach(l, f->fromlist)
- resolvenew_in_jointree(lfirst(l), varno, subtlist);
- f->quals = ResolveNew(f->quals,
- varno, 0, subtlist, CMD_SELECT, 0);
- }
- else if (IsA(jtnode, JoinExpr))
- {
- JoinExpr *j = (JoinExpr *) jtnode;
-
- resolvenew_in_jointree(j->larg, varno, subtlist);
- resolvenew_in_jointree(j->rarg, varno, subtlist);
- j->quals = ResolveNew(j->quals,
- varno, 0, subtlist, CMD_SELECT, 0);
-
- /*
- * We don't bother to update the colvars list, since it won't be
- * used again ...
- */
- }
- else
- elog(ERROR, "resolvenew_in_jointree: unexpected node type %d",
- nodeTag(jtnode));
-}
-
-/*
- * preprocess_jointree
- * Attempt to simplify a query's jointree.
- *
- * If we succeed in pulling up a subquery then we might form a jointree
- * in which a FromExpr is a direct child of another FromExpr. In that
- * case we can consider collapsing the two FromExprs into one. This is
- * an optional conversion, since the planner will work correctly either
- * way. But we may find a better plan (at the cost of more planning time)
- * if we merge the two nodes.
- *
- * NOTE: don't try to do this in the same jointree scan that does subquery
- * pullup! Since we're changing the jointree structure here, that wouldn't
- * work reliably --- see comments for pull_up_subqueries().
- */
-static Node *
-preprocess_jointree(Query *parse, Node *jtnode)
-{
- if (jtnode == NULL)
- return NULL;
- if (IsA(jtnode, RangeTblRef))
- {
- /* nothing to do here... */
- }
- else if (IsA(jtnode, FromExpr))
- {
- FromExpr *f = (FromExpr *) jtnode;
- List *newlist = NIL;
- List *l;
-
- foreach(l, f->fromlist)
- {
- Node *child = (Node *) lfirst(l);
-
- /* Recursively simplify the child... */
- child = preprocess_jointree(parse, child);
- /* Now, is it a FromExpr? */
- if (child && IsA(child, FromExpr))
- {
- /*
- * Yes, so do we want to merge it into parent? Always do
- * so if child has just one element (since that doesn't
- * make the parent's list any longer). Otherwise we have
- * to be careful about the increase in planning time
- * caused by combining the two join search spaces into
- * one. Our heuristic is to merge if the merge will
- * produce a join list no longer than GEQO_RELS/2.
- * (Perhaps need an additional user parameter?)
- */
- FromExpr *subf = (FromExpr *) child;
- int childlen = length(subf->fromlist);
- int myothers = length(newlist) + length(lnext(l));
-
- if (childlen <= 1 || (childlen + myothers) <= geqo_rels / 2)
- {
- newlist = nconc(newlist, subf->fromlist);
- f->quals = make_and_qual(f->quals, subf->quals);
- }
- else
- newlist = lappend(newlist, child);
- }
- else
- newlist = lappend(newlist, child);
- }
- f->fromlist = newlist;
- }
- else if (IsA(jtnode, JoinExpr))
- {
- JoinExpr *j = (JoinExpr *) jtnode;
-
- /* Can't usefully change the JoinExpr, but recurse on children */
- j->larg = preprocess_jointree(parse, j->larg);
- j->rarg = preprocess_jointree(parse, j->rarg);
- }
- else
- elog(ERROR, "preprocess_jointree: unexpected node type %d",
- nodeTag(jtnode));
- return jtnode;
-}
-
/*
* preprocess_expression
* Do subquery_planner's preprocessing work for an expression,
static Node *
preprocess_expression(Query *parse, Node *expr, int kind)
{
- bool has_join_rtes;
- List *rt;
+ /*
+ * 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);
/*
* Simplify constant expressions.
*
- * Note that at this point quals have 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.
+ * 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.
*/
expr = eval_const_expressions(expr);
/*
- * If it's a qual or havingQual, canonicalize it, and convert it to
- * implicit-AND format.
- *
- * XXX Is there any value in re-applying eval_const_expressions after
- * canonicalize_qual?
+ * If it's a qual or havingQual, canonicalize it.
*/
- if (kind != EXPRKIND_TARGET)
+ if (kind == EXPRKIND_QUAL)
{
- expr = (Node *) canonicalize_qual((Expr *) expr, true);
+ expr = (Node *) canonicalize_qual((Expr *) expr);
#ifdef OPTIMIZER_DEBUG
printf("After canonicalize_qual()\n");
/* Expand SubLinks to SubPlans */
if (parse->hasSubLinks)
- expr = SS_process_sublinks(expr);
+ expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));
+
+ /*
+ * 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 the query has any join RTEs, try to replace join alias variables
- * with base-relation variables, to allow quals to be pushed down.
- * We must do this after sublink processing, since it does not recurse
- * into sublinks.
- *
- * The flattening pass is expensive enough that it seems worthwhile to
- * scan the rangetable to see if we can avoid it.
+ * 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.)
*/
- has_join_rtes = false;
- foreach(rt, parse->rtable)
- {
- RangeTblEntry *rte = lfirst(rt);
-
- if (rte->rtekind == RTE_JOIN)
- {
- has_join_rtes = true;
- break;
- }
- }
- if (has_join_rtes)
- expr = flatten_join_alias_vars(expr, parse, 0);
+ if (kind == EXPRKIND_QUAL)
+ expr = (Node *) make_ands_implicit((Expr *) expr);
return expr;
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
- List *l;
+ ListCell *l;
foreach(l, f->fromlist)
preprocess_qual_conditions(parse, lfirst(l));
- f->quals = preprocess_expression(parse, f->quals, EXPRKIND_WHERE);
+ f->quals = preprocess_expression(parse, f->quals, EXPRKIND_QUAL);
}
else if (IsA(jtnode, JoinExpr))
{
preprocess_qual_conditions(parse, j->larg);
preprocess_qual_conditions(parse, j->rarg);
- j->quals = preprocess_expression(parse, j->quals, EXPRKIND_WHERE);
+ j->quals = preprocess_expression(parse, j->quals, EXPRKIND_QUAL);
}
else
- elog(ERROR, "preprocess_qual_conditions: unexpected node type %d",
- nodeTag(jtnode));
+ elog(ERROR, "unrecognized node type: %d",
+ (int) nodeTag(jtnode));
}
/*--------------------
{
int parentRTindex = parse->resultRelation;
Oid parentOID = getrelid(parentRTindex, parse->rtable);
+ int mainrtlength = list_length(parse->rtable);
List *subplans = NIL;
List *tlist = NIL;
- List *l;
+ ListCell *l;
foreach(l, inheritlist)
{
- int childRTindex = lfirsti(l);
+ int childRTindex = lfirst_int(l);
Oid childOID = getrelid(childRTindex, parse->rtable);
Query *subquery;
Plan *subplan;
/* Generate plan */
subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
subplans = lappend(subplans, subplan);
+
+ /*
+ * XXX my goodness this next bit is ugly. Really need to think about
+ * ways to rein in planner's habit of scribbling on its input.
+ *
+ * Planning of the subquery might have modified the rangetable,
+ * either by addition of RTEs due to expansion of inherited source
+ * tables, or by changes of the Query structures inside subquery
+ * RTEs. We have to ensure that this gets propagated back to the
+ * master copy. However, if we aren't done planning yet, we also
+ * need to ensure that subsequent calls to grouping_planner have
+ * virgin sub-Queries to work from. So, if we are at the last
+ * list entry, just copy the subquery rangetable back to the master
+ * copy; if we are not, then extend the master copy by adding
+ * whatever the subquery added. (We assume these added entries
+ * will go untouched by the future grouping_planner calls. We are
+ * also 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. Did I say this is ugly?)
+ */
+ if (lnext(l) == NULL)
+ parse->rtable = subquery->rtable;
+ else
+ {
+ int 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);
}
* 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).
*--------------------
*/
static Plan *
List *tlist = parse->targetList;
Plan *result_plan;
List *current_pathkeys;
- List *group_pathkeys;
List *sort_pathkeys;
- AttrNumber *groupColIdx = NULL;
if (parse->setOperations)
{
+ List *set_sortclauses;
+
/*
* 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(parse,
+ &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...
+ */
+ current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
+ result_plan->targetlist);
+ current_pathkeys = canonicalize_pathkeys(parse, current_pathkeys);
/*
* We should not need to call preprocess_targetlist, since we must
* already, but let's make sure).
*/
if (parse->rowMarks)
- elog(ERROR, "SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT");
-
- /*
- * We set current_pathkeys NIL indicating we do not know sort
- * order. This is correct when the top set operation is UNION
- * ALL, since the appended-together results are unsorted even if
- * the subplans were sorted. For other set operations we could be
- * smarter --- room for future improvement!
- */
- current_pathkeys = NIL;
+ 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 (grouping should always be null, but...)
+ * 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;
-
- /* 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)
- elog(ERROR, "SELECT FOR UPDATE is not allowed in subselects");
-
- foreach(l, parse->rowMarks)
- {
- Index rti = lfirsti(l);
- char *resname;
- Resdom *resdom;
- Var *var;
- TargetEntry *ctid;
-
- resname = (char *) palloc(32);
- sprintf(resname, "ctid%u", rti);
- resdom = makeResdom(length(tlist) + 1,
- TIDOID,
- -1,
- resname,
- true);
-
- var = makeVar(rti,
- SelfItemPointerAttributeNumber,
- TIDOID,
- -1,
- 0);
-
- ctid = makeTargetEntry(resdom, (Node *) var);
- tlist = lappend(tlist, ctid);
- }
- }
+ List *group_pathkeys;
+ AttrNumber *groupColIdx = NULL;
+ bool need_tlist_eval = true;
+ QualCost tlist_cost;
+ double sub_tuple_fraction;
+ Path *cheapest_path;
+ Path *sorted_path;
+ Path *best_path;
+ double dNumGroups = 0;
+ long numGroups = 0;
+ AggClauseCounts agg_counts;
+ int numGroupCols = list_length(parse->groupClause);
+ bool use_hashed_grouping = false;
+
+ MemSet(&agg_counts, 0, sizeof(AggClauseCounts));
+
+ /* Preprocess targetlist */
+ tlist = preprocess_targetlist(parse, tlist);
/*
* 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)
+ {
+ 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.
*
else
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 outside factors
- * such as a cursor. If the caller passed a value >= 0, believe
- * that value, else do our own examination of the query context.
- */
- if (tuple_fraction < 0.0)
- {
- /* Initial assumption is we need all the tuples */
- tuple_fraction = 0.0;
-
- /*
- * Check for 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? Should this be a SETtable parameter?)
- */
- if (parse->isPortal)
- tuple_fraction = 0.10;
- }
-
/*
* Adjust tuple_fraction if we see that we are going to apply
* limiting/grouping/aggregation/etc. This is not overridable by
}
}
+ /*
+ * 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)
{
/*
* 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
if (parse->groupClause && parse->sortClause &&
!noncanonical_pathkeys_contained_in(sort_pathkeys,
group_pathkeys))
- tuple_fraction = 0.0;
+ 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)
{
* 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 basic plan for this Query */
- result_plan = query_planner(parse,
- sub_tlist,
- tuple_fraction);
-
/*
- * query_planner returns actual sort order (which is not
- * necessarily what we requested) in query_pathkeys.
+ * Generate the best unsorted and presorted paths for this Query
+ * (but note there may not be any presorted path).
*/
- current_pathkeys = parse->query_pathkeys;
- }
+ 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.
- */
- group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
- sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
-
- /*
- * 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;
+ /*
+ * 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);
/*
- * 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 :-(
+ * If grouping, estimate the number of groups. (We can't do this
+ * until after running query_planner(), either.) Then decide
+ * whether we want to use hashed grouping.
*/
- tuplePerGroup = parse->hasAggs;
+ if (parse->groupClause)
+ {
+ List *groupExprs;
+ double cheapest_path_rows;
+
+ /*
+ * Beware 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;
+ else
+ cheapest_path_rows = 1; /* assume non-set result */
+
+ 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);
+
+ use_hashed_grouping =
+ choose_hashed_grouping(parse, tuple_fraction,
+ cheapest_path, sorted_path,
+ sort_pathkeys, group_pathkeys,
+ dNumGroups, &agg_counts);
+ }
/*
- * If there are aggregates then the Group node should just return
- * the same set of vars as the subplan did. If there are no aggs
- * then the Group node had better compute the final tlist.
+ * 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.
*/
- if (parse->hasAggs)
- group_tlist = new_unsorted_tlist(result_plan->targetlist);
+ if (use_hashed_grouping || !sorted_path)
+ best_path = cheapest_path;
else
- group_tlist = tlist;
+ best_path = sorted_path;
/*
- * Figure out whether the path result is already ordered the way
- * we need it --- if so, no need for an explicit sort step.
+ * 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 (pathkeys_contained_in(group_pathkeys, current_pathkeys))
+ result_plan = optimize_minmax_aggregates(parse,
+ tlist,
+ best_path);
+ if (result_plan != NULL)
{
- is_sorted = true; /* no sort needed now */
- /* current_pathkeys remains unchanged */
+ /*
+ * optimize_minmax_aggregates generated the full plan, with
+ * the right tlist, and it has no sort order.
+ */
+ current_pathkeys = NIL;
}
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.
+ * Normal case --- create a plan according to query_planner's
+ * results.
*/
- is_sorted = false;
- current_pathkeys = group_pathkeys;
- }
+ result_plan = create_plan(parse, best_path);
+ current_pathkeys = best_path->pathkeys;
- result_plan = make_groupplan(parse,
- group_tlist,
- tuplePerGroup,
- parse->groupClause,
- groupColIdx,
- is_sorted,
- result_plan);
- }
+ /*
+ * 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);
+ }
+ else
+ {
+ /*
+ * Otherwise, just replace the subplan's flat tlist with
+ * the desired tlist.
+ */
+ result_plan->targetlist = sub_tlist;
+ }
- /*
- * 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 */
- }
- else
- {
- /* If there are no Aggs, we shouldn't have any HAVING qual anymore */
- Assert(parse->havingQual == NULL);
- }
+ /*
+ * 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
+ {
+ /*
+ * 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);
+ }
+
+ /*
+ * Insert AGG or GROUP node if needed, plus an explicit sort step
+ * if necessary.
+ *
+ * HAVING clause, if any, becomes qual of the Agg or Group 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,
+ 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;
+
+ 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,
+ agg_counts.numAggs,
+ result_plan);
+ }
+ else if (parse->groupClause)
+ {
+ /*
+ * 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,
+ parse->groupClause,
+ groupColIdx,
+ result_plan);
+ current_pathkeys = group_pathkeys;
+ }
+
+ result_plan = (Plan *) make_group(parse,
+ tlist,
+ (List *) parse->havingQual,
+ numGroupCols,
+ groupColIdx,
+ dNumGroups,
+ result_plan);
+ /* The Group node won't change sort ordering */
+ }
+ else if (parse->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(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,
if (parse->sortClause)
{
if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
- result_plan = make_sortplan(parse, tlist, result_plan,
- parse->sortClause);
+ {
+ result_plan = (Plan *)
+ make_sort_from_sortclauses(parse,
+ parse->sortClause,
+ result_plan);
+ current_pathkeys = sort_pathkeys;
+ }
}
/*
*/
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->hasHavingQual && !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->limitOffset || parse->limitCount)
{
- result_plan = (Plan *) make_limit(tlist, result_plan,
+ 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;
}
+/*
+ * choose_hashed_grouping - should we use hashed grouping?
+ */
+static bool
+choose_hashed_grouping(Query *parse, double tuple_fraction,
+ Path *cheapest_path, Path *sorted_path,
+ List *sort_pathkeys, List *group_pathkeys,
+ double dNumGroups, AggClauseCounts *agg_counts)
+{
+ int numGroupCols = list_length(parse->groupClause);
+ double cheapest_path_rows;
+ int cheapest_path_width;
+ Size hashentrysize;
+ List *current_pathkeys;
+ Path hashed_p;
+ Path sorted_p;
+
+ /*
+ * 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)
+ return false;
+ if (agg_counts->numDistinctAggs != 0)
+ return false;
+ if (!hash_safe_grouping(parse))
+ return false;
+
+ /*
+ * 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 = cheapest_path_width;
+ /* 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, parse, 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 (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, agg_counts->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 */
+ return true;
+ }
+ return false;
+}
+
+/*
+ * 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(exprType((Node *) tle->expr), 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 grouping_planner inserts Aggregate and/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
* 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;
*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 && !parse->havingQual)
+ if (!parse->hasAggs && !parse->groupClause && !parse->hasHavingQual)
+ {
+ *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;
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),
- 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;
}
}
}
/*
- * 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.
- */
-static Plan *
-make_groupplan(Query *parse,
- List *group_tlist,
- bool tuplePerGroup,
- List *groupClause,
- AttrNumber *grpColIdx,
- bool is_presorted,
- Plan *subplan)
-{
- int numCols = length(groupClause);
-
- if (!is_presorted)
- {
- /*
- * 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, groupClause)
- {
- 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 = grpcl->sortop;
- }
- }
-
- Assert(keyno > 0);
-
- subplan = (Plan *) make_sort(parse, sort_tlist, subplan, keyno);
- }
-
- return (Plan *) make_group(group_tlist, tuplePerGroup, numCols,
- grpColIdx, subplan);
-}
-
-/*
- * make_sortplan
- * Add a Sort node to implement an explicit ORDER BY clause.
+ * 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.
*/
-Plan *
-make_sortplan(Query *parse, List *tlist, Plan *plannode, List *sortcls)
+static void
+locate_grouping_columns(Query *parse,
+ List *tlist,
+ List *sub_tlist,
+ AttrNumber *groupColIdx)
{
- List *sort_tlist;
- List *i;
int keyno = 0;
+ ListCell *gl;
/*
- * First make a copy of the tlist so that we don't corrupt the
- * original.
+ * No work unless grouping.
*/
- sort_tlist = new_unsorted_tlist(tlist);
+ if (!parse->groupClause)
+ {
+ Assert(groupColIdx == NULL);
+ return;
+ }
+ Assert(groupColIdx != NULL);
- foreach(i, sortcls)
+ foreach(gl, parse->groupClause)
{
- SortClause *sortcl = (SortClause *) lfirst(i);
- TargetEntry *tle = get_sortgroupclause_tle(sortcl, sort_tlist);
- Resdom *resdom = tle->resdom;
+ GroupClause *grpcl = (GroupClause *) lfirst(gl);
+ Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
+ TargetEntry *te = NULL;
+ ListCell *sl;
- /*
- * 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)
+ foreach(sl, sub_tlist)
{
- /* OK, insert the ordering info needed by the executor. */
- resdom->reskey = ++keyno;
- resdom->reskeyop = sortcl->sortop;
+ te = (TargetEntry *) lfirst(sl);
+ if (equal(groupexpr, te->expr))
+ break;
}
- }
-
- Assert(keyno > 0);
+ if (!sl)
+ elog(ERROR, "failed to locate grouping columns");
- return (Plan *) make_sort(parse, sort_tlist, plannode, keyno);
+ groupColIdx[keyno++] = te->resno;
+ }
}
/*
* 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 elog if we
+ * new tlist to evaluate the resjunk columns. For now, just ereport if we
* find any resjunk columns in orig_tlist.
*/
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)
- elog(ERROR, "postprocess_setop_tlist: resjunk output columns 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(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->resno == orig_tle->resno);
+ new_tle->ressortgroupref = orig_tle->ressortgroupref;
}
- if (orig_tlist != NIL)
- elog(ERROR, "postprocess_setop_tlist: resjunk output columns not implemented");
+ if (orig_tlist_item != NULL)
+ elog(ERROR, "resjunk output columns are not implemented");
return new_tlist;
}
projects / postgresql / blobdiff