From 27d04ed5310ad33dd3364322ae53ea685b28a8b6 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Thu, 18 Jan 2024 11:30:53 +0100 Subject: [PATCH] Rework text in replication slots documentation This is cosmetic, so no backpatch. Reviewed-by: Bharath Rupireddy Discussion: https://postgr.es/m/20230413111838.e7yxke2dtwrxw3qy@alvherre.pgsql Discussion: https://postgr.es/m/202401151537.ryhysqfncs6d@alvherre.pgsql --- doc/src/sgml/high-availability.sgml | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index 9dd52ff275..236c0af65f 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -924,7 +924,8 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' streaming replication - Replication slots provide an automated way to ensure that the primary does + Replication slots provide an automated way to ensure that the + primary server does not remove WAL segments until they have been received by all standbys, and that the primary does not remove rows which could cause a recovery conflict even when the @@ -935,21 +936,28 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass' of old WAL segments using , or by storing the segments in an archive using or . - However, these methods often result in retaining more WAL segments than + A disadvantage of these methods is that they + often result in retaining more WAL segments than required, whereas replication slots retain only the number of segments - known to be needed. On the other hand, replication slots can retain so - many WAL segments that they fill up the space allocated - for pg_wal; - limits the size of WAL files - retained by replication slots. + known to be needed. Similarly, on its own, without also using a replication slot, provides protection against relevant rows being removed by vacuum, but provides no protection during any time period - when the standby is not connected. Replication slots overcome these - disadvantages. + when the standby is not connected. + + + + Beware that replication slots can cause the server to retain so + many WAL segments that they fill up the space allocated for + pg_wal. + can be used to limit the size + of WAL files retained by replication slots. + + + Querying and Manipulating Replication Slots