database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-02 09:02:37 +03:00
Code Activity

Add support for multivariate MCV lists

Browse Source 
Introduce a third extended statistic type, supported by the CREATE
STATISTICS command - MCV lists, a generalization of the statistic
already built and used for individual columns.

Compared to the already supported types (n-distinct coefficients and
functional dependencies), MCV lists are more complex, include column
values and allow estimation of much wider range of common clauses
(equality and inequality conditions, IS NULL, IS NOT NULL etc.).
Similarly to the other types, a new pseudo-type (pg_mcv_list) is used.

Author: Tomas Vondra
Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera
Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
This commit is contained in:
Tomas Vondra
2019-03-27 18:32:18 +01:00
parent 333ed246c6
commit 7300a69950
32 changed files with 3597 additions and 134 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/backend/utils/adt/ruleutils.c
View File

@ -1509,6 +1509,7 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
bool isnull;
bool ndistinct_enabled;
bool dependencies_enabled;
bool mcv_enabled;
int i;
statexttup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(statextid));
@ -1544,6 +1545,7 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
ndistinct_enabled = false;
dependencies_enabled = false;
mcv_enabled = false;
for (i = 0; i < ARR_DIMS(arr)[0]; i++)
{
@ -1551,6 +1553,8 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
ndistinct_enabled = true;
if (enabled[i] == STATS_EXT_DEPENDENCIES)
dependencies_enabled = true;
if (enabled[i] == STATS_EXT_MCV)
mcv_enabled = true;
}
/*
@ -1560,13 +1564,27 @@ pg_get_statisticsobj_worker(Oid statextid, bool missing_ok)
* statistics types on a newer postgres version, if the statistics had all
* options enabled on the original version.
*/
if (!ndistinct_enabled || !dependencies_enabled)
if (!ndistinct_enabled || !dependencies_enabled || !mcv_enabled)
{
bool gotone = false;
appendStringInfoString(&buf, " (");
if (ndistinct_enabled)
{
appendStringInfoString(&buf, "ndistinct");
else if (dependencies_enabled)
appendStringInfoString(&buf, "dependencies");
gotone = true;
}
if (dependencies_enabled)
{
appendStringInfo(&buf, "%sdependencies", gotone ? ", " : "");
gotone = true;
}
if (mcv_enabled)
appendStringInfo(&buf, "%smcv", gotone ? ", " : "");
appendStringInfoChar(&buf, ')');
}