From 7363021df306885f6872d558bae8b5747c92ab3c Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Sat, 20 Feb 2010 10:07:27 +0000 Subject: [PATCH] Copy editing of Hot Standby docs. Some clarifications, addition of missing items and minor edits. --- doc/src/sgml/high-availability.sgml | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index 7fc34603f8..535321da39 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1,4 +1,4 @@ - + High Availability, Load Balancing, and Replication @@ -1079,8 +1079,8 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' The data on the standby takes some time to arrive from the primary server so there will be a measurable delay between primary and standby. Running the same query nearly simultaneously on both primary and standby might therefore - return differing results. Eventually, the standby will be - consistent with the primary. + return differing results. We say that data on the standby is + eventually consistent with the primary. Queries executed on the standby will be correct with regard to the transactions that had been recovered at the start of the query, or start of first statement in the case of serializable transactions. In comparison with the primary, @@ -1203,12 +1203,12 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' - LOCK TABLE that explicitly requests a mode higher than ROW EXCLUSIVE MODE. + LOCK that explicitly requests a mode higher than ROW EXCLUSIVE MODE. - LOCK TABLE in short default form, since it requests ACCESS EXCLUSIVE MODE. + LOCK in short default form, since it requests ACCESS EXCLUSIVE MODE. @@ -1245,7 +1245,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' - Sequence update - nextval() + Sequence updates - nextval(), setval() @@ -1262,8 +1262,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' subtle differences in behavior between read-only transactions run on a standby and run during normal operation. It is possible that LISTEN, UNLISTEN, - NOTIFY, and temporary tables might be allowed in a - future release. + and temporary tables might be allowed in a future release. @@ -1483,7 +1482,8 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' Three-way deadlocks are possible between AccessExclusiveLocks arriving from the primary, cleanup WAL records that require buffer cleanup locks, and user requests that are waiting behind replayed AccessExclusiveLocks. Deadlocks - are resolved by time-out when they exceed max_standby_delay. + are resolved immediately, should they occur, though they are thought to be + rare in practice. @@ -1516,8 +1516,9 @@ LOG: database system is ready to accept read only connections Consistency information is recorded once per checkpoint on the primary, as long - as recovery_connections is enabled on the primary. If this parameter - is disabled, it is not possible to enable recovery connections on the standby. + as recovery_connections is enabled on the primary. It is not possible + to enable recovery connections on the standby when reading WAL written during the + period that recovery_connections was disabled on the primary. Reaching a consistent state can also be delayed in the presence of both of these conditions: -- 2.11.0