diff options
Diffstat (limited to 'src/backend/statistics')
| -rw-r--r-- | src/backend/statistics/extended_stats.c | 150 | ||||
| -rw-r--r-- | src/backend/statistics/mcv.c | 15 |
2 files changed, 154 insertions, 11 deletions
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c index dd29b2f9fff..207ee3160ef 100644 --- a/src/backend/statistics/extended_stats.c +++ b/src/backend/statistics/extended_stats.c @@ -62,6 +62,7 @@ typedef struct StatExtEntry char *name; /* statistics object's name */ Bitmapset *columns; /* attribute numbers covered by the object */ List *types; /* 'char' list of enabled statistic kinds */ + int stattarget; /* statistics target (-1 for default) */ } StatExtEntry; @@ -71,7 +72,8 @@ static VacAttrStats **lookup_var_attr_stats(Relation rel, Bitmapset *attrs, static void statext_store(Oid relid, MVNDistinct *ndistinct, MVDependencies *dependencies, MCVList *mcv, VacAttrStats **stats); - +static int statext_compute_stattarget(int stattarget, + int natts, VacAttrStats **stats); /* * Compute requested extended stats, using the rows sampled for the plain @@ -107,6 +109,7 @@ BuildRelationExtStatistics(Relation onerel, double totalrows, MCVList *mcv = NULL; VacAttrStats **stats; ListCell *lc2; + int stattarget; /* * Check if we can build these stats based on the column analyzed. If @@ -131,6 +134,19 @@ BuildRelationExtStatistics(Relation onerel, double totalrows, Assert(bms_num_members(stat->columns) >= 2 && bms_num_members(stat->columns) <= STATS_MAX_DIMENSIONS); + /* compute statistics target for this statistics */ + stattarget = statext_compute_stattarget(stat->stattarget, + bms_num_members(stat->columns), + stats); + + /* + * Don't rebuild statistics objects with statistics target set to 0 (we + * just leave the existing values around, just like we do for regular + * per-column statistics). + */ + if (stattarget == 0) + continue; + /* compute statistic of each requested type */ foreach(lc2, stat->types) { @@ -144,7 +160,7 @@ BuildRelationExtStatistics(Relation onerel, double totalrows, stat->columns, stats); else if (t == STATS_EXT_MCV) mcv = statext_mcv_build(numrows, rows, stat->columns, stats, - totalrows); + totalrows, stattarget); } /* store the statistics in the catalog */ @@ -158,6 +174,135 @@ BuildRelationExtStatistics(Relation onerel, double totalrows, } /* + * ComputeExtStatisticsRows + * Compute number of rows required by extended statistics on a table. + * + * Computes number of rows we need to sample to build extended statistics on a + * table. This only looks at statistics we can actually build - for example + * when analyzing only some of the columns, this will skip statistics objects + * that would require additional columns. + * + * See statext_compute_stattarget for details about how we compute statistics + * target for a statistics objects (from the object target, attribute targets + * and default statistics target). + */ +int +ComputeExtStatisticsRows(Relation onerel, + int natts, VacAttrStats **vacattrstats) +{ + Relation pg_stext; + ListCell *lc; + List *lstats; + MemoryContext cxt; + MemoryContext oldcxt; + int result = 0; + + cxt = AllocSetContextCreate(CurrentMemoryContext, + "ComputeExtStatisticsRows", + ALLOCSET_DEFAULT_SIZES); + oldcxt = MemoryContextSwitchTo(cxt); + + pg_stext = table_open(StatisticExtRelationId, RowExclusiveLock); + lstats = fetch_statentries_for_relation(pg_stext, RelationGetRelid(onerel)); + + foreach(lc, lstats) + { + StatExtEntry *stat = (StatExtEntry *) lfirst(lc); + int stattarget = stat->stattarget; + VacAttrStats **stats; + int nattrs = bms_num_members(stat->columns); + + /* + * Check if we can build this statistics object based on the columns + * analyzed. If not, ignore it (don't report anything, we'll do that + * during the actual build BuildRelationExtStatistics). + */ + stats = lookup_var_attr_stats(onerel, stat->columns, + natts, vacattrstats); + + if (!stats) + continue; + + /* + * Compute statistics target, based on what's set for the statistic + * object itself, and for its attributes. + */ + stattarget = statext_compute_stattarget(stat->stattarget, + nattrs, stats); + + /* Use the largest value for all statistics objects. */ + if (stattarget > result) + result = stattarget; + } + + table_close(pg_stext, RowExclusiveLock); + + MemoryContextSwitchTo(oldcxt); + MemoryContextDelete(cxt); + + /* compute sample size based on the statistics target */ + return (300 * result); +} + +/* + * statext_compute_stattarget + * compute statistics target for an extended statistic + * + * When computing target for extended statistics objects, we consider three + * places where the target may be set - the statistics object itself, + * attributes the statistics is defined on, and then the default statistics + * target. + * + * First we look at what's set for the statistics object itself, using the + * ALTER STATISTICS ... SET STATISTICS command. If we find a valid value + * there (i.e. not -1) we're done. Otherwise we look at targets set for any + * of the attributes the statistic is defined on, and if there are columns + * with defined target, we use the maximum value. We do this mostly for + * backwards compatibility, because this is what we did before having + * statistics target for extended statistics. + * + * And finally, if we still don't have a statistics target, we use the value + * set in default_statistics_target. + */ +static int +statext_compute_stattarget(int stattarget, int nattrs, VacAttrStats **stats) +{ + int i; + + /* + * If there's statistics target set for the statistics object, use it. + * It may be set to 0 which disables building of that statistic. + */ + if (stattarget >= 0) + return stattarget; + + /* + * The target for the statistics object is set to -1, in which case we + * look at the maximum target set for any of the attributes the object + * is defined on. + */ + for (i = 0; i < nattrs; i++) + { + /* keep the maximmum statistics target */ + if (stats[i]->attr->attstattarget > stattarget) + stattarget = stats[i]->attr->attstattarget; + } + + /* + * If the value is still negative (so neither the statistics object nor + * any of the columns have custom statistics target set), use the global + * default target. + */ + if (stattarget < 0) + stattarget = default_statistics_target; + + /* As this point we should have a valid statistics target. */ + Assert((stattarget >= 0) && (stattarget <= 10000)); + + return stattarget; +} + +/* * statext_is_kind_built * Is this stat kind built in the given pg_statistic_ext_data tuple? */ @@ -225,6 +370,7 @@ fetch_statentries_for_relation(Relation pg_statext, Oid relid) entry->statOid = staForm->oid; entry->schema = get_namespace_name(staForm->stxnamespace); entry->name = pstrdup(NameStr(staForm->stxname)); + entry->stattarget = staForm->stxstattarget; for (i = 0; i < staForm->stxkeys.dim1; i++) { entry->columns = bms_add_member(entry->columns, diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c index bae6f219684..ee35f6afc56 100644 --- a/src/backend/statistics/mcv.c +++ b/src/backend/statistics/mcv.c @@ -181,7 +181,7 @@ get_mincount_for_mcv_list(int samplerows, double totalrows) */ MCVList * statext_mcv_build(int numrows, HeapTuple *rows, Bitmapset *attrs, - VacAttrStats **stats, double totalrows) + VacAttrStats **stats, double totalrows, int stattarget) { int i, numattrs, @@ -210,15 +210,12 @@ statext_mcv_build(int numrows, HeapTuple *rows, Bitmapset *attrs, groups = build_distinct_groups(nitems, items, mss, &ngroups); /* - * Maximum number of MCV items to store, based on the attribute with the - * largest stats target (and the number of groups we have available). + * Maximum number of MCV items to store, based on the statistics target + * we computed for the statistics object (from target set for the object + * itself, attributes and the system default). In any case, we can't keep + * more groups than we have available. */ - nitems = stats[0]->attr->attstattarget; - for (i = 1; i < numattrs; i++) - { - if (stats[i]->attr->attstattarget > nitems) - nitems = stats[i]->attr->attstattarget; - } + nitems = stattarget; if (nitems > ngroups) nitems = ngroups; |