Don't waste the last segment of each 4GB logical log file.

The comments claimed that wasting the last segment made it easier to do
calculations with XLogRecPtrs, because you don't have problems representing
last-byte-position-plus-1 that way. In my experience, however, it only made
things more complicated, because the there was two ways to represent the
boundary at the beginning of a logical log file: logid = n+1 and xrecoff = 0,
or as xlogid = n and xrecoff = 4GB - XLOG_SEG_SIZE. Some functions were
picky about which representation was used.

Also, use a 64-bit segment number instead of the log/seg combination, to
point to a certain WAL segment. We assume that all platforms have a working
64-bit integer type nowadays.

This is an incompatible change in WAL format, so bumping WAL version number.

1 files changed, 16 insertions, 14 deletions

diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 650b74fff7..b3ba7089df 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -69,11 +69,12 @@ walrcv_disconnect_type walrcv_disconnect = NULL;
 
 /*
  * These variables are used similarly to openLogFile/Id/Seg/Off,
- * but for walreceiver to write the XLOG.
+ * but for walreceiver to write the XLOG. recvFileTLI is the TimeLineID
+ * corresponding the filename of recvFile, used for error messages.
  */
 static int	recvFile = -1;
-static uint32 recvId = 0;
-static uint32 recvSeg = 0;
+static TimeLineID	recvFileTLI = -1;
+static XLogSegNo recvSegNo = 0;
 static uint32 recvOff = 0;
 
 /*
@@ -481,7 +482,7 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
 	{
 		int			segbytes;
 
-		if (recvFile < 0 || !XLByteInSeg(recptr, recvId, recvSeg))
+		if (recvFile < 0 || !XLByteInSeg(recptr, recvSegNo))
 		{
 			bool		use_existent;
 
@@ -501,15 +502,16 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
 				if (close(recvFile) != 0)
 					ereport(PANIC,
 							(errcode_for_file_access(),
-						errmsg("could not close log file %u, segment %u: %m",
-							   recvId, recvSeg)));
+							 errmsg("could not close log segment %s: %m",
+									XLogFileNameP(recvFileTLI, recvSegNo))));
 			}
 			recvFile = -1;
 
 			/* Create/use new log file */
-			XLByteToSeg(recptr, recvId, recvSeg);
+			XLByteToSeg(recptr, recvSegNo);
 			use_existent = true;
-			recvFile = XLogFileInit(recvId, recvSeg, &use_existent, true);
+			recvFile = XLogFileInit(recvSegNo, &use_existent, true);
+			recvFileTLI = ThisTimeLineID;
 			recvOff = 0;
 		}
 
@@ -527,9 +529,9 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
 			if (lseek(recvFile, (off_t) startoff, SEEK_SET) < 0)
 				ereport(PANIC,
 						(errcode_for_file_access(),
-						 errmsg("could not seek in log file %u, "
-								"segment %u to offset %u: %m",
-								recvId, recvSeg, startoff)));
+						 errmsg("could not seek in log segment %s, to offset %u: %m",
+								XLogFileNameP(recvFileTLI, recvSegNo),
+								startoff)));
 			recvOff = startoff;
 		}
 
@@ -544,9 +546,9 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
 				errno = ENOSPC;
 			ereport(PANIC,
 					(errcode_for_file_access(),
-					 errmsg("could not write to log file %u, segment %u "
+					 errmsg("could not write to log segment %s "
 							"at offset %u, length %lu: %m",
-							recvId, recvSeg,
+							XLogFileNameP(recvFileTLI, recvSegNo),
 							recvOff, (unsigned long) segbytes)));
 		}
 
@@ -575,7 +577,7 @@ XLogWalRcvFlush(bool dying)
 		/* use volatile pointer to prevent code rearrangement */
 		volatile WalRcvData *walrcv = WalRcv;
 
-		issue_xlog_fsync(recvFile, recvId, recvSeg);
+		issue_xlog_fsync(recvFile, recvSegNo);
 
 		LogstreamResult.Flush = LogstreamResult.Write;