Make WAL segment size configurable at initdb time.

For performance reasons a larger segment size than the default 16MB
can be useful. A larger segment size has two main benefits: Firstly,
in setups using archiving, it makes it easier to write scripts that
can keep up with higher amounts of WAL, secondly, the WAL has to be
written and synced to disk less frequently.

But at the same time large segment size are disadvantageous for
smaller databases. So far the segment size had to be configured at
compile time, often making it unrealistic to choose one fitting to a
particularly load. Therefore change it to a initdb time setting.

This includes a breaking changes to the xlogreader.h API, which now
requires the current segment size to be configured.  For that and
similar reasons a number of binaries had to be taught how to recognize
the current segment size.

Author: Beena Emerson, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Kuntal Ghosh, Michael
    Paquier, Peter Eisentraut, Robert Hass, Tushar Ahuja
Discussion: https://postgr.es/m/CAOG9ApEAcQ--1ieKbhFzXSQPw_YLmepaa4hNdnY5+ZULpt81Mw@mail.gmail.com

1 files changed, 10 insertions, 9 deletions

diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 657bafae579..68766d522d5 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2083,15 +2083,16 @@ ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
 		 * store in segment in which it belongs by start lsn, don't split over
 		 * multiple segments tho
 		 */
-		if (fd == -1 || !XLByteInSeg(change->lsn, curOpenSegNo))
+		if (fd == -1 ||
+			!XLByteInSeg(change->lsn, curOpenSegNo, wal_segment_size))
 		{
 			XLogRecPtr	recptr;
 
 			if (fd != -1)
 				CloseTransientFile(fd);
 
-			XLByteToSeg(change->lsn, curOpenSegNo);
-			XLogSegNoOffsetToRecPtr(curOpenSegNo, 0, recptr);
+			XLByteToSeg(change->lsn, curOpenSegNo, wal_segment_size);
+			XLogSegNoOffsetToRecPtr(curOpenSegNo, 0, recptr, wal_segment_size);
 
 			/*
 			 * No need to care about TLIs here, only used during a single run,
@@ -2319,7 +2320,7 @@ ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
 	txn->nentries_mem = 0;
 	Assert(dlist_is_empty(&txn->changes));
 
-	XLByteToSeg(txn->final_lsn, last_segno);
+	XLByteToSeg(txn->final_lsn, last_segno, wal_segment_size);
 
 	while (restored < max_changes_in_memory && *segno <= last_segno)
 	{
@@ -2334,11 +2335,11 @@ ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
 			/* first time in */
 			if (*segno == 0)
 			{
-				XLByteToSeg(txn->first_lsn, *segno);
+				XLByteToSeg(txn->first_lsn, *segno, wal_segment_size);
 			}
 
 			Assert(*segno != 0 || dlist_is_empty(&txn->changes));
-			XLogSegNoOffsetToRecPtr(*segno, 0, recptr);
+			XLogSegNoOffsetToRecPtr(*segno, 0, recptr, wal_segment_size);
 
 			/*
 			 * No need to care about TLIs here, only used during a single run,
@@ -2575,8 +2576,8 @@ ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn)
 	Assert(txn->first_lsn != InvalidXLogRecPtr);
 	Assert(txn->final_lsn != InvalidXLogRecPtr);
 
-	XLByteToSeg(txn->first_lsn, first);
-	XLByteToSeg(txn->final_lsn, last);
+	XLByteToSeg(txn->first_lsn, first, wal_segment_size);
+	XLByteToSeg(txn->final_lsn, last, wal_segment_size);
 
 	/* iterate over all possible filenames, and delete them */
 	for (cur = first; cur <= last; cur++)
@@ -2584,7 +2585,7 @@ ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn)
 		char		path[MAXPGPATH];
 		XLogRecPtr	recptr;
 
-		XLogSegNoOffsetToRecPtr(cur, 0, recptr);
+		XLogSegNoOffsetToRecPtr(cur, 0, recptr, wal_segment_size);
 
 		sprintf(path, "pg_replslot/%s/xid-%u-lsn-%X-%X.snap",
 				NameStr(MyReplicationSlot->data.name), txn->xid,