Add pg_stats_ext view for extended statistics
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
parent
6cbfb784c3
commit
aa087ec64f
|
|
@ -6373,6 +6373,28 @@ SCRAM-SHA-256$<replaceable><iteration count></replaceable>:<replaceable>&l
|
|||
about those tables that are readable by the current user.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<structname>pg_statistic</structname> should not be readable by the
|
||||
public, since even statistical information about a table's contents
|
||||
might be considered sensitive. (Example: minimum and maximum values
|
||||
of a salary column might be quite interesting.)
|
||||
<link linkend="view-pg-stats"><structname>pg_stats</structname></link>
|
||||
is a publicly readable view on
|
||||
<structname>pg_statistic</structname> that only exposes information
|
||||
about those tables that are readable by the current user.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
Similarly, <structname>pg_statistic_ext_data</structname> should not be
|
||||
readable by the public, since the contents might be considered sensitive.
|
||||
(Example: most common combination of values in columns might be quite
|
||||
interesting.)
|
||||
<link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link>
|
||||
is a publicly readable view on <structname>pg_statistic_ext_data</structname>
|
||||
(after joining with <structname>pg_statistic_ext</structname>) that only exposes
|
||||
information about those tables and columns that are readable by the current user.
|
||||
</para>
|
||||
|
||||
<table>
|
||||
<title><structname>pg_statistic</structname> Columns</title>
|
||||
|
||||
|
|
@ -8343,6 +8365,11 @@ SCRAM-SHA-256$<replaceable><iteration count></replaceable>:<replaceable>&l
|
|||
<entry>planner statistics</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link></entry>
|
||||
<entry>extended planner statistics</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><link linkend="view-pg-tables"><structname>pg_tables</structname></link></entry>
|
||||
<entry>tables</entry>
|
||||
|
|
@ -10922,6 +10949,171 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
|
|||
|
||||
</sect1>
|
||||
|
||||
<sect1 id="view-pg-stats-ext">
|
||||
<title><structname>pg_stats_ext</structname></title>
|
||||
|
||||
<indexterm zone="view-pg-stats-ext">
|
||||
<primary>pg_stats_ext</primary>
|
||||
</indexterm>
|
||||
|
||||
<para>
|
||||
The view <structname>pg_stats_ext</structname> provides access to
|
||||
the information stored in the <link
|
||||
linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>
|
||||
and <link linkend="catalog-pg-statistic-ext-data"><structname>pg_statistic_ext_data</structname></link>
|
||||
catalogs. This view allows access only to rows of
|
||||
<structname>pg_statistic_ext</structname> and <structname>pg_statistic_ext_data</structname>
|
||||
that correspond to tables the user has permission to read, and therefore
|
||||
it is safe to allow public read access to this view.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<structname>pg_stats_ext</structname> is also designed to present the
|
||||
information in a more readable format than the underlying catalog
|
||||
— at the cost that its schema must be extended whenever new types
|
||||
of extended statistics are added to <structname>pg_statistic_ext</structname>.
|
||||
</para>
|
||||
|
||||
<table>
|
||||
<title><structname>pg_stats_ext</structname> Columns</title>
|
||||
|
||||
<tgroup cols="4">
|
||||
<thead>
|
||||
<row>
|
||||
<entry>Name</entry>
|
||||
<entry>Type</entry>
|
||||
<entry>References</entry>
|
||||
<entry>Description</entry>
|
||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry><structfield>schemaname</structfield></entry>
|
||||
<entry><type>name</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
|
||||
<entry>Name of schema containing table</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>tablename</structfield></entry>
|
||||
<entry><type>name</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.relname</literal></entry>
|
||||
<entry>Name of table</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>statistics_schemaname</structfield></entry>
|
||||
<entry><type>name</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.nspname</literal></entry>
|
||||
<entry>Name of schema containing extended statistic</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>statistics_name</structfield></entry>
|
||||
<entry><type>name</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>.stxname</literal></entry>
|
||||
<entry>Name of extended statistics</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>statistics_owner</structfield></entry>
|
||||
<entry><type>oid</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>
|
||||
<entry>Owner of the extended statistics</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>attnames</structfield></entry>
|
||||
<entry><type>name[]</type></entry>
|
||||
<entry><literal><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.attname</literal></entry>
|
||||
<entry>Names of the column the extended statistics is defined on</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>kinds</structfield></entry>
|
||||
<entry><type>text[]</type></entry>
|
||||
<entry></entry>
|
||||
<entry>Types of exdended statistics enabled for this record</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>n_distinct</structfield></entry>
|
||||
<entry><type>pg_ndistinct</type></entry>
|
||||
<entry></entry>
|
||||
<entry>N-distinct counts for combinations of columns. If greater than
|
||||
zero, the estimated number of distinct values in the combination. If
|
||||
less than zero, the negative of the number of distinct values divided
|
||||
by the number of rows.
|
||||
(The negated form is used when <command>ANALYZE</command> believes that
|
||||
the number of distinct values is likely to increase as the table grows;
|
||||
the positive form is used when the column seems to have a fixed number
|
||||
of possible values.) For example, -1 indicates a unique combination of
|
||||
columns in which the number of distinct combinations is the same as the
|
||||
number of rows.
|
||||
</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>dependencies</structfield></entry>
|
||||
<entry><type>pg_dependencies</type></entry>
|
||||
<entry></entry>
|
||||
<entry>Functional dependency statistics</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>most_common_vals</structfield></entry>
|
||||
<entry><type>anyarray</type></entry>
|
||||
<entry></entry>
|
||||
<entry>
|
||||
A list of the most common combinations in the columns. (Null if
|
||||
no values seem to be more common than any others.)
|
||||
</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>most_common_val_nulls</structfield></entry>
|
||||
<entry><type>anyarray</type></entry>
|
||||
<entry></entry>
|
||||
<entry>
|
||||
A list of NULL flags for the most common combinations of values.
|
||||
(Null when <structfield>most_common_vals</structfield> is.)
|
||||
</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>most_common_freqs</structfield></entry>
|
||||
<entry><type>real[]</type></entry>
|
||||
<entry></entry>
|
||||
<entry>
|
||||
A list of the frequencies of the most common combinations,
|
||||
i.e., number of occurrences of each divided by total number of rows.
|
||||
(Null when <structfield>most_common_vals</structfield> is.)
|
||||
</entry>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
<entry><structfield>most_common_base_freqs</structfield></entry>
|
||||
<entry><type>real[]</type></entry>
|
||||
<entry></entry>
|
||||
<entry>
|
||||
A list of the base frequencies of the most common combinations,
|
||||
i.e., product of per-value frequencies.
|
||||
(Null when <structfield>most_common_vals</structfield> is.)
|
||||
</entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
|
||||
<para>
|
||||
The maximum number of entries in the array fields can be controlled on a
|
||||
column-by-column basis using the <command>ALTER TABLE SET STATISTICS</command>
|
||||
command, or globally by setting the
|
||||
<xref linkend="guc-default-statistics-target"/> run-time parameter.
|
||||
</para>
|
||||
|
||||
</sect1>
|
||||
|
||||
<sect1 id="view-pg-tables">
|
||||
<title><structname>pg_tables</structname></title>
|
||||
|
||||
|
|
|
|||
|
|
@ -253,6 +253,47 @@ CREATE VIEW pg_stats WITH (security_barrier) AS
|
|||
|
||||
REVOKE ALL on pg_statistic FROM public;
|
||||
|
||||
CREATE VIEW pg_stats_ext WITH (security_barrier) AS
|
||||
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)
|
||||
FROM unnest(s.stxkeys) k
|
||||
JOIN pg_attribute a
|
||||
ON (a.attrelid = s.stxrelid AND a.attnum = 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(values) AS most_common_vals,
|
||||
array_agg(nulls) AS most_common_val_nulls,
|
||||
array_agg(frequency) AS most_common_freqs,
|
||||
array_agg(base_frequency) AS most_common_base_freqs
|
||||
FROM pg_mcv_list_items(sd.stxdmcv)
|
||||
) m ON sd.stxdmcv IS NOT NULL
|
||||
WHERE NOT EXISTS
|
||||
( SELECT 1
|
||||
FROM unnest(stxkeys) k
|
||||
JOIN pg_attribute a
|
||||
ON (a.attrelid = s.stxrelid AND a.attnum = k)
|
||||
WHERE NOT has_column_privilege(c.oid, a.attnum, 'select') )
|
||||
AND (c.relrowsecurity = false OR NOT row_security_active(c.oid));
|
||||
|
||||
REVOKE ALL on pg_statistic_ext FROM public;
|
||||
GRANT SELECT (oid, stxrelid, stxname, stxnamespace, stxowner, stxkeys, stxkind)
|
||||
ON pg_statistic_ext TO public;
|
||||
|
||||
CREATE VIEW pg_publication_tables AS
|
||||
SELECT
|
||||
P.pubname AS pubname,
|
||||
|
|
|
|||
|
|
@ -53,6 +53,6 @@
|
|||
*/
|
||||
|
||||
/* yyyymmddN */
|
||||
#define CATALOG_VERSION_NO 201906151
|
||||
#define CATALOG_VERSION_NO 201906152
|
||||
|
||||
#endif
|
||||
|
|
|
|||
|
|
@ -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,
|
||||
|
|
|
|||
Loading…
Reference in New Issue