From 24c5f1a103ce6656a5cb430d9a996c34e61ab2a5 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Wed, 30 Mar 2016 20:07:05 -0300 Subject: Enable logical slots to follow timeline switches MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When decoding from a logical slot, it's necessary for xlog reading to be able to read xlog from historical (i.e. not current) timelines; otherwise, decoding fails after failover, because the archives are in the historical timeline. This is required to make "failover logical slots" possible; it currently has no other use, although theoretically it could be used by an extension that creates a slot on a standby and continues to replay from the slot when the standby is promoted. This commit includes a module in src/test/modules with functions to manipulate the slots (which is not otherwise possible in SQL code) in order to enable testing, and a new test in src/test/recovery to ensure that the behavior is as expected. Author: Craig Ringer Reviewed-By: Oleksii Kliukin, Andres Freund, Petr Jelínek --- src/backend/replication/logical/logicalfuncs.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'src/backend/replication/logical/logicalfuncs.c') diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c index 3853ab4cf5f..dd6cd62ccd1 100644 --- a/src/backend/replication/logical/logicalfuncs.c +++ b/src/backend/replication/logical/logicalfuncs.c @@ -231,12 +231,6 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin rsinfo->setResult = p->tupstore; rsinfo->setDesc = p->tupdesc; - /* compute the current end-of-wal */ - if (!RecoveryInProgress()) - end_of_wal = GetFlushRecPtr(); - else - end_of_wal = GetXLogReplayRecPtr(NULL); - ReplicationSlotAcquire(NameStr(*name)); PG_TRY(); @@ -273,7 +267,8 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin * slot's confirmed_flush. This means we might read xlog we don't * actually decode rows from, but the snapshot builder might need it * to get to a consistent point. The point we start returning data to - * *users* at is the candidate restart lsn from the decoding context. + * *users* at is the confirmed_flush lsn set up in the decoding + * context. */ startptr = MyReplicationSlot->data.restart_lsn; @@ -282,8 +277,14 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin /* invalidate non-timetravel entries */ InvalidateSystemCaches(); + if (!RecoveryInProgress()) + end_of_wal = GetFlushRecPtr(); + else + end_of_wal = GetXLogReplayRecPtr(NULL); + + /* Decode until we run out of records */ while ((startptr != InvalidXLogRecPtr && startptr < end_of_wal) || - (ctx->reader->EndRecPtr && ctx->reader->EndRecPtr < end_of_wal)) + (ctx->reader->EndRecPtr != InvalidXLogRecPtr && ctx->reader->EndRecPtr < end_of_wal)) { XLogRecord *record; char *errm = NULL; -- cgit v1.2.3