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Clean up bugs in clause_selectivity() cleanup.

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Commit ac2b09508 was not terribly carefully reviewed.  Band-aid it to
not fail on non-RestrictInfo input, per report from Andreas Seltenreich.
Also make it do something more reasonable with variable-free clauses,
and improve nearby comments.

Discussion: https://postgr.es/m/87inmf5rdx.fsf@credativ.de
This commit is contained in:
Tom Lane 2017-04-08 16:38:03 -04:00
parent aba696d1af
commit eef8c0069e
1 changed files with 42 additions and 39 deletions
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81
src/backend/optimizer/path/clausesel.c
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@ -41,8 +41,8 @@ typedef struct RangeQueryClause
static void addRangeClause(RangeQueryClause **rqlist, Node *clause,
bool varonleft, bool isLTsel, Selectivity s2);
static RelOptInfo *find_relation_from_clauses(PlannerInfo *root,
List *clauses);
static RelOptInfo *find_single_rel_for_clauses(PlannerInfo *root,
List *clauses);
/****************************************************************************
* ROUTINES TO COMPUTE SELECTIVITIES
@ -63,10 +63,8 @@ static RelOptInfo *find_relation_from_clauses(PlannerInfo *root,
* probabilities, and in reality they are often NOT independent. So,
* we want to be smarter where we can.
*
* When 'rel' is not null and rtekind = RTE_RELATION, we'll try to apply
* selectivity estimates using any extended statistcs on 'rel'.
*
* If we identify such extended statistics exist, we try to apply them.
* If the clauses taken together refer to just one relation, we'll try to
* apply selectivity estimates using any extended statistics for that rel.
* Currently we only have (soft) functional dependencies, so apply these in as
* many cases as possible, and fall back on normal estimates for remaining
* clauses.
@ -105,41 +103,36 @@ clauselist_selectivity(PlannerInfo *root,
SpecialJoinInfo *sjinfo)
{
Selectivity s1 = 1.0;
RelOptInfo *rel;
Bitmapset *estimatedclauses = NULL;
RangeQueryClause *rqlist = NULL;
ListCell *l;
Bitmapset *estimatedclauses = NULL;
int listidx;
RelOptInfo *rel;
/*
* If there's exactly one clause, then extended statistics is futile at
* this level (we might be able to apply them later if it's AND/OR
* clause). So just go directly to clause_selectivity().
* If there's exactly one clause, just go directly to
* clause_selectivity(). None of what we might do below is relevant.
*/
if (list_length(clauses) == 1)
return clause_selectivity(root, (Node *) linitial(clauses),
varRelid, jointype, sjinfo);
/*
* Determine if these clauses reference a single relation. If so we might
* like to try applying any extended statistics which exist on it.
* Called many time during joins, so must return NULL quickly if not.
*/
rel = find_relation_from_clauses(root, clauses);
/*
* When a relation of RTE_RELATION is given as 'rel', we'll try to
* perform selectivity estimation using extended statistics.
* Determine if these clauses reference a single relation. If so, and if
* it has extended statistics, try to apply those.
*/
rel = find_single_rel_for_clauses(root, clauses);
if (rel && rel->rtekind == RTE_RELATION && rel->statlist != NIL)
{
/*
* Perform selectivity estimations on any clauses found applicable by
* dependencies_clauselist_selectivity. The 0-based list position of
* estimated clauses will be populated in 'estimatedclauses'.
* dependencies_clauselist_selectivity. 'estimatedclauses' will be
* filled with the 0-based list positions of clauses used that way, so
* that we can ignore them below.
*/
s1 *= dependencies_clauselist_selectivity(root, clauses, varRelid,
jointype, sjinfo, rel, &estimatedclauses);
jointype, sjinfo, rel,
&estimatedclauses);
/*
* This would be the place to apply any other types of extended
@ -426,36 +419,46 @@ addRangeClause(RangeQueryClause **rqlist, Node *clause,
}
/*
* find_relation_from_clauses
* Process each clause in 'clauses' and determine if all clauses
* reference only a single relation. If so return that relation,
* find_single_rel_for_clauses
* Examine each clause in 'clauses' and determine if all clauses
* reference only a single relation. If so return that relation,
* otherwise return NULL.
*/
static RelOptInfo *
find_relation_from_clauses(PlannerInfo *root, List *clauses)
find_single_rel_for_clauses(PlannerInfo *root, List *clauses)
{
ListCell *l;
int relid;
int lastrelid = 0;
int lastrelid = 0;
ListCell *l;
foreach(l, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
int relid;
if (bms_get_singleton_member(rinfo->clause_relids, &relid))
{
if (lastrelid != 0 && relid != lastrelid)
return NULL; /* relation not the same as last one */
lastrelid = relid;
}
else
return NULL; /* multiple relations in clause */
/*
* If we have a list of bare clauses rather than RestrictInfos, we
* could pull out their relids the hard way with pull_varnos().
* However, currently the extended-stats machinery won't do anything
* with non-RestrictInfo clauses anyway, so there's no point in
* spending extra cycles; just fail if that's what we have.
*/
if (!IsA(rinfo, RestrictInfo))
return NULL;
if (bms_is_empty(rinfo->clause_relids))
continue; /* we can ignore variable-free clauses */
if (!bms_get_singleton_member(rinfo->clause_relids, &relid))
return NULL; /* multiple relations in this clause */
if (lastrelid == 0)
lastrelid = relid; /* first clause referencing a relation */
else if (relid != lastrelid)
return NULL; /* relation not same as last one */
}
if (lastrelid != 0)
return find_base_rel(root, lastrelid);
return NULL; /* no clauses */
return NULL; /* no clauses */
}
/*