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Minor improvements for the multivariate MCV lists

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The MCV build should always call get_mincount_for_mcv_list(), as the
there is no other logic to decide whether the MCV list represents all
the data. So just remove the (ngroups > nitems) condition.

Also, when building MCV lists, the number of items was limited by the
statistics target (i.e. up to 10000). But when deserializing the MCV
list, a different value (8192) was used to check the input, causing
an error.  Simply ensure that the same value is used in both places.

This should have been included in 7300a69950, but I forgot to include it
in that commit.
This commit is contained in:
Tomas Vondra
2019-03-27 20:07:41 +01:00
parent 7300a69950
commit a63b29a1de
2 changed files with 33 additions and 35 deletions
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4
src/include/statistics/statistics.h
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@@ -82,8 +82,8 @@ typedef struct MVDependencies
#define STATS_MCV_MAGIC 0xE1A651C2 /* marks serialized bytea */
#define STATS_MCV_TYPE_BASIC 1 /* basic MCV list type */
/* max items in MCV list (mostly arbitrary number) */
#define STATS_MCVLIST_MAX_ITEMS 8192
/* max items in MCV list (should be equal to max default_statistics_target) */
#define STATS_MCVLIST_MAX_ITEMS 10000
/*
* Multivariate MCV (most-common value) lists