*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.259 2005/08/01 20:31:08 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.260 2005/08/27 22:13:43 tgl Exp $
*
* NOTES
* Every node type that can appear in stored rules' parsetrees *must*
WRITE_NODE_FIELD(full_join_clauses);
WRITE_NODE_FIELD(in_info_list);
WRITE_NODE_FIELD(query_pathkeys);
+ WRITE_NODE_FIELD(group_pathkeys);
+ WRITE_NODE_FIELD(sort_pathkeys);
+ WRITE_FLOAT_FIELD(tuple_fraction, "%.4f");
WRITE_BOOL_FIELD(hasJoinRTEs);
WRITE_BOOL_FIELD(hasOuterJoins);
WRITE_BOOL_FIELD(hasHavingQual);
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.71 2005/07/28 22:27:00 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.72 2005/08/27 22:13:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
return PATHKEYS_BETTER2; /* key2 is longer */
}
-/*
- * compare_noncanonical_pathkeys
- * Compare two pathkeys to see if they are equivalent, and if not whether
- * one is "better" than the other. This is used when we must compare
- * non-canonicalized pathkeys.
- *
- * A pathkey can be considered better than another if it is a superset:
- * it contains all the keys of the other plus more. For example, either
- * ((A) (B)) or ((A B)) is better than ((A)).
- *
- * Currently, the only user of this routine is grouping_planner(),
- * and it will only pass single-element sublists (from
- * make_pathkeys_for_sortclauses). Therefore we don't have to do the
- * full two-way-subset-inclusion test on each pair of sublists that is
- * implied by the above statement. Instead we just verify they are
- * singleton lists and then do an equal(). This could be improved if
- * necessary.
- */
-PathKeysComparison
-compare_noncanonical_pathkeys(List *keys1, List *keys2)
-{
- ListCell *key1,
- *key2;
-
- forboth(key1, keys1, key2, keys2)
- {
- List *subkey1 = (List *) lfirst(key1);
- List *subkey2 = (List *) lfirst(key2);
-
- Assert(list_length(subkey1) == 1);
- Assert(list_length(subkey2) == 1);
- if (!equal(subkey1, subkey2))
- return PATHKEYS_DIFFERENT; /* no need to keep looking */
- }
-
- /*
- * If we reached the end of only one list, the other is longer and
- * therefore not a subset. (We assume the additional sublist(s) of
- * the other list are not NIL --- no pathkey list should ever have a
- * NIL sublist.)
- */
- if (key1 == NULL && key2 == NULL)
- return PATHKEYS_EQUAL;
- if (key1 != NULL)
- return PATHKEYS_BETTER1; /* key1 is longer */
- return PATHKEYS_BETTER2; /* key2 is longer */
-}
-
/*
* pathkeys_contained_in
* Common special case of compare_pathkeys: we just want to know
return false;
}
-/*
- * noncanonical_pathkeys_contained_in
- * The same, when we don't have canonical pathkeys.
- */
-bool
-noncanonical_pathkeys_contained_in(List *keys1, List *keys2)
-{
- switch (compare_noncanonical_pathkeys(keys1, keys2))
- {
- case PATHKEYS_EQUAL:
- case PATHKEYS_BETTER2:
- return true;
- default:
- break;
- }
- return false;
-}
-
/*
* get_cheapest_path_for_pathkeys
* Find the cheapest path (according to the specified criterion) that
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.86 2005/07/02 23:00:41 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planmain.c,v 1.87 2005/08/27 22:13:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
+#include "optimizer/tlist.h"
+#include "utils/selfuncs.h"
-/*--------------------
+/*
* query_planner
* Generate a path (that is, a simplified plan) for a basic query,
* which may involve joins but not any fancier features.
* *cheapest_path receives the overall-cheapest path for the query
* *sorted_path receives the cheapest presorted path for the query,
* if any (NULL if there is no useful presorted path)
+ * *num_groups receives the estimated number of groups, or 1 if query
+ * does not use grouping
*
* Note: the PlannerInfo node also includes a query_pathkeys field, which is
* both an input and an output of query_planner(). The input value signals
* PlannerInfo field and not a passed parameter is that the low-level routines
* in indxpath.c need to see it.)
*
+ * Note: the PlannerInfo node also includes group_pathkeys and sort_pathkeys,
+ * which like query_pathkeys need to be canonicalized once the info is
+ * available.
+ *
* tuple_fraction is interpreted as follows:
* 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)
- *--------------------
*/
void
query_planner(PlannerInfo *root, List *tlist, double tuple_fraction,
- Path **cheapest_path, Path **sorted_path)
+ Path **cheapest_path, Path **sorted_path,
+ double *num_groups)
{
Query *parse = root->parse;
List *constant_quals;
/* Make tuple_fraction accessible to lower-level routines */
root->tuple_fraction = tuple_fraction;
+ *num_groups = 1; /* default result */
+
/*
* If the query has an empty join tree, then it's something easy like
* "SELECT 2+2;" or "INSERT ... VALUES()". Fall through quickly.
/*
* We should now have all the pathkey equivalence sets built, so it's
* now possible to convert the requested query_pathkeys to canonical
- * form.
+ * form. Also canonicalize the groupClause and sortClause pathkeys
+ * for use later.
*/
root->query_pathkeys = canonicalize_pathkeys(root, root->query_pathkeys);
+ root->group_pathkeys = canonicalize_pathkeys(root, root->group_pathkeys);
+ root->sort_pathkeys = canonicalize_pathkeys(root, root->sort_pathkeys);
/*
* Ready to do the primary planning.
elog(ERROR, "failed to construct the join relation");
/*
- * Now that we have an estimate of the final rel's size, we can
- * convert a tuple_fraction specified as an absolute count (ie, a
- * LIMIT option) into a fraction of the total tuples.
+ * If there's grouping going on, estimate the number of result groups.
+ * We couldn't do this any earlier because it depends on relation size
+ * estimates that were set up above.
+ *
+ * Then convert tuple_fraction to fractional form if it is absolute,
+ * and adjust it based on the knowledge that grouping_planner will be
+ * doing grouping or aggregation work with our result.
+ *
+ * This introduces some undesirable coupling between this code and
+ * grouping_planner, but the alternatives seem even uglier; we couldn't
+ * pass back completed paths without making these decisions here.
*/
- if (tuple_fraction >= 1.0)
- tuple_fraction /= final_rel->rows;
+ if (parse->groupClause)
+ {
+ List *groupExprs;
+
+ groupExprs = get_sortgrouplist_exprs(parse->groupClause,
+ parse->targetList);
+ *num_groups = estimate_num_groups(root,
+ groupExprs,
+ final_rel->rows);
+
+ /*
+ * In GROUP BY mode, an absolute LIMIT is relative to the number
+ * of groups not the number of tuples. If the caller gave us
+ * a fraction, keep it as-is. (In both cases, we are effectively
+ * assuming that all the groups are about the same size.)
+ */
+ if (tuple_fraction >= 1.0)
+ tuple_fraction /= *num_groups;
+
+ /*
+ * If both GROUP BY and ORDER BY are specified, we will need two
+ * levels of sort --- and, therefore, certainly need to read all
+ * the tuples --- unless ORDER BY is a subset of GROUP BY.
+ */
+ if (parse->groupClause && parse->sortClause &&
+ !pathkeys_contained_in(root->sort_pathkeys, root->group_pathkeys))
+ tuple_fraction = 0.0;
+ }
+ else if (parse->hasAggs || root->hasHavingQual)
+ {
+ /*
+ * Ungrouped aggregate will certainly want to read all the tuples,
+ * and it will deliver a single result row (so leave *num_groups 1).
+ */
+ tuple_fraction = 0.0;
+ }
+ else if (parse->distinctClause)
+ {
+ /*
+ * Since there was no grouping or aggregation, it's reasonable to
+ * assume the UNIQUE filter has effects comparable to GROUP BY.
+ * Return the estimated number of output rows for use by caller.
+ * (If DISTINCT is used with grouping, we ignore its effects for
+ * rowcount estimation purposes; this amounts to assuming the grouped
+ * rows are distinct already.)
+ */
+ List *distinctExprs;
+
+ distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
+ parse->targetList);
+ *num_groups = estimate_num_groups(root,
+ distinctExprs,
+ final_rel->rows);
+
+ /*
+ * Adjust tuple_fraction the same way as for GROUP BY, too.
+ */
+ if (tuple_fraction >= 1.0)
+ tuple_fraction /= *num_groups;
+ }
+ else
+ {
+ /*
+ * Plain non-grouped, non-aggregated query: an absolute tuple
+ * fraction can be divided by the number of tuples.
+ */
+ if (tuple_fraction >= 1.0)
+ tuple_fraction /= final_rel->rows;
+ }
/*
* Pick out the cheapest-total path and the cheapest presorted path
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.191 2005/08/18 17:51:11 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.192 2005/08/27 22:13:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
int *offset_est, int *count_est);
static bool choose_hashed_grouping(PlannerInfo *root, 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(PlannerInfo *root);
static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
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)
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);
&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.
*/
- 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(parse->groupClause, tlist);
+ root->sort_pathkeys =
+ make_pathkeys_for_sortclauses(parse->sortClause, tlist);
/*
* Will need actual number of aggregates for estimating costs.
* Needs more thought...)
*/
if (parse->groupClause)
- root->query_pathkeys = group_pathkeys;
+ root->query_pathkeys = root->group_pathkeys;
else if (parse->sortClause)
- root->query_pathkeys = sort_pathkeys;
+ root->query_pathkeys = root->sort_pathkeys;
else
root->query_pathkeys = NIL;
- /*
- * With grouping or aggregation, the tuple fraction to pass to
- * query_planner() may be different from what it is at top level.
- */
- sub_tuple_fraction = tuple_fraction;
-
- if (parse->groupClause)
- {
- /*
- * In GROUP BY mode, we have the little problem that we don't
- * really know how many input tuples will be needed to make a
- * 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;
- }
-
/*
* Generate the best unsorted and presorted paths for this Query
- * (but note there may not be any presorted path).
+ * (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.
*/
- query_planner(root, sub_tlist, sub_tuple_fraction,
- &cheapest_path, &sorted_path);
+ query_planner(root, sub_tlist, tuple_fraction,
+ &cheapest_path, &sorted_path, &dNumGroups);
- /*
- * We couldn't canonicalize group_pathkeys and sort_pathkeys
- * before running query_planner(), so do it now.
- */
- group_pathkeys = canonicalize_pathkeys(root, group_pathkeys);
- sort_pathkeys = canonicalize_pathkeys(root, sort_pathkeys);
+ group_pathkeys = root->group_pathkeys;
+ sort_pathkeys = root->sort_pathkeys;
/*
- * 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.
+ * If grouping, decide whether we want to use hashed grouping.
*/
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(root,
- 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(root, tuple_fraction,
cheapest_path, sorted_path,
- sort_pathkeys, group_pathkeys,
dNumGroups, &agg_counts);
+
+ /* Also convert # groups to long int --- but 'ware overflow! */
+ numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
}
/*
/*
* 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.
+ * use the number of distinct-groups calculated by query_planner.
*/
if (!parse->groupClause && !root->hasHavingQual && !parse->hasAggs)
- {
- List *distinctExprs;
-
- distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
- parse->targetList);
- result_plan->plan_rows = estimate_num_groups(root,
- distinctExprs,
- result_plan->plan_rows);
- }
+ result_plan->plan_rows = dNumGroups;
}
/*
static bool
choose_hashed_grouping(PlannerInfo *root, double tuple_fraction,
Path *cheapest_path, Path *sorted_path,
- List *sort_pathkeys, List *group_pathkeys,
double dNumGroups, AggClauseCounts *agg_counts)
{
int numGroupCols = list_length(root->parse->groupClause);
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, root, sort_pathkeys, hashed_p.total_cost,
+ if (root->sort_pathkeys)
+ cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
dNumGroups, cheapest_path_width);
if (sorted_path)
sorted_p.total_cost = cheapest_path->total_cost;
current_pathkeys = cheapest_path->pathkeys;
}
- if (!pathkeys_contained_in(group_pathkeys,
- current_pathkeys))
+ if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
{
- cost_sort(&sorted_p, root, group_pathkeys, sorted_p.total_cost,
+ cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
cheapest_path_rows, cheapest_path_width);
- current_pathkeys = group_pathkeys;
+ current_pathkeys = root->group_pathkeys;
}
if (root->parse->hasAggs)
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, root, sort_pathkeys, sorted_p.total_cost,
+ 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);
/*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.117 2005/07/23 21:05:48 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.118 2005/08/27 22:13:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
List *query_pathkeys; /* desired pathkeys for query_planner(),
* and actual pathkeys afterwards */
+ List *group_pathkeys; /* groupClause pathkeys, if any */
+ List *sort_pathkeys; /* sortClause pathkeys, if any */
+
double tuple_fraction; /* tuple_fraction passed to query_planner */
bool hasJoinRTEs; /* true if any RTEs are RTE_JOIN kind */
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.86 2005/07/28 20:26:22 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.87 2005/08/27 22:13:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
extern List *canonicalize_pathkeys(PlannerInfo *root, List *pathkeys);
extern PathKeysComparison compare_pathkeys(List *keys1, List *keys2);
extern bool pathkeys_contained_in(List *keys1, List *keys2);
-extern PathKeysComparison compare_noncanonical_pathkeys(List *keys1,
- List *keys2);
-extern bool noncanonical_pathkeys_contained_in(List *keys1, List *keys2);
extern Path *get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
CostSelector cost_criterion);
extern Path *get_cheapest_fractional_path_for_pathkeys(List *paths,
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.87 2005/08/18 17:51:12 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.88 2005/08/27 22:13:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
*/
extern void query_planner(PlannerInfo *root, List *tlist,
double tuple_fraction,
- Path **cheapest_path, Path **sorted_path);
+ Path **cheapest_path, Path **sorted_path,
+ double *num_groups);
/*
* prototypes for plan/planagg.c
projects / postgresql / commitdiff