Improve pg_autovacuum documentation to clarify that the enabled field cannot

prevent anti-wraparound vacuuming, and to caution against setting unreasonably
small values of freeze_max_age.  Also put in a notice that this catalog is
likely to disappear entirely in some future release.  Per discussion of
bug #3898 from Steven Flatt.

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29dd25f1cb4a978bb04bf351a3eb0bef7b283679..de045d7057d2135b22a7c91f695943c33366e454 100644 (file)
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1,4 +1,4 @@
-
+
 
@@ -1245,6 +1245,14 @@
    about the autovacuum daemon, see .
   
 
+  
+   
+    It is likely that pg_autovacuum will disappear
+    in a future release, with the information instead being kept in
+    pg_class.reloptions entries.
+   
+  
+
       <structname>pg_autovacuum</> Columns @@ -1270,7 +1278,8 @@       enabled       bool       -      If false, this table is never autovacuumed+      If false, this table will not be autovacuumed, except+       to prevent transaction ID wraparound             @@ -1352,7 +1361,9 @@    to prevent transaction ID wraparound if the table's    pg_class.relfrozenxid field attains an age    of more than freeze_max_age transactions, whether the table-   has been changed or not.  The system will launch autovacuum to perform+   has been changed or not, even if+   pg_autovacuum.enabled is set to+   false for it.  The system will launch autovacuum to perform    such VACUUMs even if autovacuum is otherwise disabled.    See  for more about wraparound    prevention.@@ -1364,12 +1375,15 @@    be used for this particular value.  Observe that the    vac_cost_delay variable inherits its default value from the     configuration parameter,-   or from  if the former is set to a negative-   value.  The same applies to vac_cost_limit.+   or from  if the former is set to a+   negative value.  The same applies to vac_cost_limit.    Also, autovacuum will ignore attempts to set a per-table-   freeze_max_age larger than the system-wide setting (it can only be set-   smaller), and the freeze_min_age value will be limited to half the-   system-wide  setting.+   freeze_max_age larger than the system-wide setting (it can+   only be set smaller), and the freeze_min_age value will be+   limited to half the system-wide 
+   linkend="guc-autovacuum-freeze-max-age"> setting.  Note that while you
+   can set freeze_max_age very small, or even zero, this
+   is usually unwise since it will force frequent vacuuming.
   
 
  

This is the main PostgreSQL git repository.
RSS
Atom












































window.onload = function () {
	var tz_cookie = { name: 'gitweb_tz', expires: 14, path: '/' };
	onloadTZSetup('local', tz_cookie, 'datetime');
};