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Add pg_stats_ext view for extended statistics

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Regular per-column statistics are stored in pg_statistics catalog, which
is however rather difficult to read, so we also have pg_stats view with
a human-reablable version of the data.

For extended statistic the catalog was fairly easy to read, so we did
not have such human-readable view so far.  Commit 9b6babfa2d however did
split the catalog into two, which makes querying harder.  Furthermore,
we want to show the multi-column MCV list in a way similar to per-column
stats (and not as a bytea value).

This commit introduces pg_stats_ext view, joining the two catalogs and
massaging the data to produce human-readable output similar to pg_stats.
It also considers RLS and access privileges - the data is shown only when
the user has access to all columns the extended statistic is defined on.

Bumped CATVERSION due to adding new system view.

Author: Dean Rasheed, with improvements by me
Reviewed-by: Dean Rasheed, John Naylor
Discussion: https://postgr.es/m/CAEZATCUhT9rt7Ui%3DVdx4N%3D%3DVV5XOK5dsXfnGgVOz_JhAicB%3DZA%40mail.gmail.com
This commit is contained in:
Tomas Vondra
2019-06-13 17:25:04 +02:00
parent 6cbfb784c3
commit aa087ec64f
4 changed files with 263 additions and 1 deletions
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29
src/test/regress/expected/rules.out
View File

@ -2284,6 +2284,35 @@ pg_stats| SELECT n.nspname AS schemaname,
JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum))))
LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace)))
WHERE ((NOT a.attisdropped) AND has_column_privilege(c.oid, a.attnum, 'select'::text) AND ((c.relrowsecurity = false) OR (NOT row_security_active(c.oid))));
pg_stats_ext| SELECT cn.nspname AS schemaname,
c.relname AS tablename,
sn.nspname AS statistics_schemaname,
s.stxname AS statistics_name,
pg_get_userbyid(s.stxowner) AS statistics_owner,
( SELECT array_agg(a.attname ORDER BY a.attnum) AS array_agg
FROM (unnest(s.stxkeys) k(k)
JOIN pg_attribute a ON (((a.attrelid = s.stxrelid) AND (a.attnum = k.k))))) AS attnames,
s.stxkind AS kinds,
sd.stxdndistinct AS n_distinct,
sd.stxddependencies AS dependencies,
m.most_common_vals,
m.most_common_val_nulls,
m.most_common_freqs,
m.most_common_base_freqs
FROM (((((pg_statistic_ext s
JOIN pg_class c ON ((c.oid = s.stxrelid)))
JOIN pg_statistic_ext_data sd ON ((s.oid = sd.stxoid)))
LEFT JOIN pg_namespace cn ON ((cn.oid = c.relnamespace)))
LEFT JOIN pg_namespace sn ON ((sn.oid = s.stxnamespace)))
LEFT JOIN LATERAL ( SELECT array_agg(pg_mcv_list_items."values") AS most_common_vals,
array_agg(pg_mcv_list_items.nulls) AS most_common_val_nulls,
array_agg(pg_mcv_list_items.frequency) AS most_common_freqs,
array_agg(pg_mcv_list_items.base_frequency) AS most_common_base_freqs
FROM pg_mcv_list_items(sd.stxdmcv) pg_mcv_list_items(index, "values", nulls, frequency, base_frequency)) m ON ((sd.stxdmcv IS NOT NULL)))
WHERE ((NOT (EXISTS ( SELECT 1
FROM (unnest(s.stxkeys) k(k)
JOIN pg_attribute a ON (((a.attrelid = s.stxrelid) AND (a.attnum = k.k))))
WHERE (NOT has_column_privilege(c.oid, a.attnum, 'select'::text))))) AND ((c.relrowsecurity = false) OR (NOT row_security_active(c.oid))));
pg_tables| SELECT n.nspname AS schemaname,
c.relname AS tablename,
pg_get_userbyid(c.relowner) AS tableowner,