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Avoid permission failure in pg_sequences.last_value

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Before, reading pg_sequences.last_value would fail unless the user had
appropriate sequence permissions, which would make the pg_sequences view
cumbersome to use.  Instead, return null instead of the real value when
there are no permissions.

From: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Shinoda, Noriyoshi <noriyoshi.shinoda@hpe.com>
This commit is contained in:
Peter Eisentraut 2017-02-06 15:17:27 -05:00
parent ad6af3fc42
commit ab82340a43
3 changed files with 13 additions and 3 deletions
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5
doc/src/sgml/catalogs.sgml
View File

@ -9882,7 +9882,10 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
<entry></entry>
<entry>The last sequence value written to disk. If caching is used,
this value can be greater than the last value handed out from the
sequence. Null if the sequence has not been read from yet.</entry>
sequence. Null if the sequence has not been read from yet. Also, if
the current user does not have <literal>USAGE</literal>
or <literal>SELECT</literal> privilege on the sequence, the value is
null.</entry>
</row>
</tbody>
</tgroup>

6
src/backend/catalog/system_views.sql
View File

@ -175,7 +175,11 @@ CREATE OR REPLACE VIEW pg_sequences AS
S.seqincrement AS increment_by,
S.seqcycle AS cycle,
S.seqcache AS cache_size,
pg_sequence_last_value(C.oid) AS last_value
CASE
WHEN has_sequence_privilege(C.oid, 'SELECT,USAGE'::text)
THEN pg_sequence_last_value(C.oid)
ELSE NULL
END AS last_value
FROM pg_sequence S JOIN pg_class C ON (C.oid = S.seqrelid)
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE NOT pg_is_other_temp_schema(N.oid)

5
src/test/regress/expected/rules.out
View File

@ -1647,7 +1647,10 @@ pg_sequences| SELECT n.nspname AS schemaname,
s.seqincrement AS increment_by,
s.seqcycle AS cycle,
s.seqcache AS cache_size,
pg_sequence_last_value((c.oid)::regclass) AS last_value
CASE
WHEN has_sequence_privilege(c.oid, 'SELECT,USAGE'::text) THEN pg_sequence_last_value((c.oid)::regclass)
ELSE NULL::bigint
END AS last_value
FROM ((pg_sequence s
JOIN pg_class c ON ((c.oid = s.seqrelid)))
LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace)))