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Update comments for pg_statistic catalog table

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Make a reminder that pg_stats view needs to be modified whenever a new slot
kind is added.  To prevent situations like 918eee0c49 when pg_stats was
forgotten to be updated.

Also, revise the comment that only non-null, non-empty rows are considered
for the range length histogram.

Discussion: https://postgr.es/m/flat/b67d8b57-9357-7e82-a2e7-f6ce6eaeec67@postgrespro.ru
Author: Egor Rogov, Soumyadeep Chakraborty
Reviewed-by: Tomas Vondra, Justin Pryzby, Jian He
This commit is contained in:
Alexander Korotkov 2023-11-27 01:29:56 +02:00
parent 3558f120f8
commit 441c8a3134
1 changed files with 5 additions and 1 deletions
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6
src/include/catalog/pg_statistic.h
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@ -152,6 +152,9 @@ DECLARE_FOREIGN_KEY((starelid, staattnum), pg_attribute, (attrelid, attnum));
* data "kind" will appear in any particular slot. Instead, search the
* stakind fields to see if the desired data is available. (The standard
* function get_attstatsslot() may be used for this.)
*
* Note: The pg_stats view needs to be modified whenever a new slot kind is
* added to core.
*/
/*
@ -262,7 +265,8 @@ DECLARE_FOREIGN_KEY((starelid, staattnum), pg_attribute, (attrelid, attnum));
* a format similar to STATISTIC_KIND_HISTOGRAM: it contains M (>=2) range
* values that divide the column data values into M-1 bins of approximately
* equal population. The lengths are stored as float8s, as measured by the
* range type's subdiff function. Only non-null rows are considered.
* range type's subdiff function. Only non-null, non-empty rows are
* considered.
*/
#define STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM 6