diff options
| -rw-r--r-- | doc/src/sgml/catalogs.sgml | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index 7a380ce2f94..713ee25939e 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -7085,13 +7085,18 @@ </para> <para> - When the <structname>pg_locks</structname> view is accessed, the - internal lock manager data structures are momentarily locked, and - a copy is made for the view to display. This ensures that the - view produces a consistent set of results, while not blocking - normal lock manager operations longer than necessary. Nonetheless - there could be some impact on database performance if this view is - frequently accessed. + The <structname>pg_locks</structname> view displays data from both the + regular lock manager and the predicate lock manager, which are + separate systems. When this view is accessed, the internal data + structures of each lock manager are momentarily locked, and copies are + made for the view to display. Each lock manager will therefore + produce a consistent set of results, but as we do not lock both lock + managers simultaneously, it is possible for locks to be taken or + released after we interrogate the regular lock manager and before we + interrogate the predicate lock manager. Each lock manager is only + locked for the minimum possible time so as to reduce the performance + impact of querying this view, but there could nevertheless be some + impact on database performance if it is frequently accessed. </para> <para> |