Rename wal_keep_segments to wal_keep_size.

max_slot_wal_keep_size that was added in v13 and wal_keep_segments are
the GUC parameters to specify how much WAL files to retain for
the standby servers. While max_slot_wal_keep_size accepts the number of
bytes of WAL files, wal_keep_segments accepts the number of WAL files.
This difference of setting units between those similar parameters could
be confusing to users.

To alleviate this situation, this commit renames wal_keep_segments to
wal_keep_size, and make users specify the WAL size in it instead of
the number of WAL files.

There was also the idea to rename max_slot_wal_keep_size to
max_slot_wal_keep_segments, in the discussion. But we have been moving
away from measuring in segments, for example, checkpoint_segments was
replaced by max_wal_size. So we concluded to rename wal_keep_segments
to wal_keep_size.

Back-patch to v13 where max_slot_wal_keep_size was added.

Author: Fujii Masao
Reviewed-by: Álvaro Herrera, Kyotaro Horiguchi, David Steele
Discussion: https://postgr.es/m/574b4ea3-e0f9-b175-ead2-ebea7faea855@oss.nttdata.com

1 files changed, 7 insertions, 6 deletions

diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 9fe147bf44e..f88694672fb 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -413,19 +413,20 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 		else
 		{
 			XLogSegNo   targetSeg;
-			XLogSegNo   keepSegs;
+			uint64   slotKeepSegs;
+			uint64   keepSegs;
 			XLogSegNo   failSeg;
 			XLogRecPtr  failLSN;
 
 			XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size);
 
-			/* determine how many segments slots can be kept by slots ... */
-			keepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
-			/* ... and override by wal_keep_segments as needed */
-			keepSegs = Max(keepSegs, wal_keep_segments);
+			/* determine how many segments slots can be kept by slots */
+			slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
+			/* ditto for wal_keep_size */
+			keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size);
 
 			/* if currpos reaches failLSN, we lose our segment */
-			failSeg = targetSeg + keepSegs + 1;
+			failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1;
 			XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN);
 
 			values[i++] = Int64GetDatum(failLSN - currlsn);