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Collect and use multi-column dependency stats

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Follow on patch in the multi-variate statistics patch series.

CREATE STATISTICS s1 WITH (dependencies) ON (a, b) FROM t;
ANALYZE;
will collect dependency stats on (a, b) and then use the measured
dependency in subsequent query planning.

Commit 7b504eb282 added
CREATE STATISTICS with n-distinct coefficients. These are now
specified using the mutually exclusive option WITH (ndistinct).

Author: Tomas Vondra, David Rowley
Reviewed-by: Kyotaro HORIGUCHI, Álvaro Herrera, Dean Rasheed, Robert Haas
and many other comments and contributions
Discussion: https://postgr.es/m/56f40b20-c464-fad2-ff39-06b668fac47c@2ndquadrant.com
This commit is contained in:
Simon Riggs
2017-04-05 18:00:42 -04:00
parent 00b6b6feb1
commit 2686ee1b7c
31 changed files with 2035 additions and 79 deletions
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54
src/backend/utils/adt/ruleutils.c
View File

@ -1452,6 +1452,13 @@ pg_get_statisticsext_worker(Oid statextid, bool missing_ok)
StringInfoData buf;
int colno;
char *nsp;
ArrayType *arr;
char *enabled;
Datum datum;
bool isnull;
bool ndistinct_enabled;
bool dependencies_enabled;
int i;
statexttup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(statextid));
@ -1467,10 +1474,55 @@ pg_get_statisticsext_worker(Oid statextid, bool missing_ok)
initStringInfo(&buf);
nsp = get_namespace_name(statextrec->stanamespace);
appendStringInfo(&buf, "CREATE STATISTICS %s ON (",
appendStringInfo(&buf, "CREATE STATISTICS %s",
quote_qualified_identifier(nsp,
NameStr(statextrec->staname)));
/*
* Lookup the staenabled column so that we know how to handle the WITH
* clause.
*/
datum = SysCacheGetAttr(STATEXTOID, statexttup,
Anum_pg_statistic_ext_staenabled, &isnull);
Assert(!isnull);
arr = DatumGetArrayTypeP(datum);
if (ARR_NDIM(arr) != 1 ||
ARR_HASNULL(arr) ||
ARR_ELEMTYPE(arr) != CHAROID)
elog(ERROR, "staenabled is not a 1-D char array");
enabled = (char *) ARR_DATA_PTR(arr);
ndistinct_enabled = false;
dependencies_enabled = false;
for (i = 0; i < ARR_DIMS(arr)[0]; i++)
{
if (enabled[i] == STATS_EXT_NDISTINCT)
ndistinct_enabled = true;
if (enabled[i] == STATS_EXT_DEPENDENCIES)
dependencies_enabled = true;
}
/*
* If any option is disabled, then we'll need to append a WITH clause to
* show which options are enabled. We omit the WITH clause on purpose
* when all options are enabled, so a pg_dump/pg_restore will create all
* statistics types on a newer postgres version, if the statistics had all
* options enabled on the original version.
*/
if (!ndistinct_enabled || !dependencies_enabled)
{
appendStringInfoString(&buf, " WITH (");
if (ndistinct_enabled)
appendStringInfoString(&buf, "ndistinct");
else if (dependencies_enabled)
appendStringInfoString(&buf, "dependencies");
appendStringInfoChar(&buf, ')');
}
appendStringInfoString(&buf, " ON (");
for (colno = 0; colno < statextrec->stakeys.dim1; colno++)
{
AttrNumber attnum = statextrec->stakeys.values[colno];