From 2d29f5f59a9007d7e70b49ce8c487afbbb291e32 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 21 Jan 2010 08:19:57 +0000 Subject: [PATCH] Fix bogus comments. --- src/backend/replication/walsender.c | 45 ++++++++++++----------------- 1 file changed, 18 insertions(+), 27 deletions(-) diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index c028ab3dce..a10dc3d8b2 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -30,7 +30,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.2 2010/01/15 11:47:15 heikki Exp $ + * $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.3 2010/01/21 08:19:57 heikki Exp $ * *------------------------------------------------------------------------- */ @@ -602,7 +602,7 @@ XLogSend(StringInfo outMsg) sentPtr.xrecoff == 0) return true; - /* Attempt to send all the records which were written to the disk */ + /* Attempt to send all records flushed to the disk already */ SendRqstPtr = GetWriteRecPtr(); /* Quick exit if nothing to do */ @@ -610,18 +610,10 @@ XLogSend(StringInfo outMsg) return true; /* - * Since successive pages in a segment are consecutively written, - * we can gather multiple records together by issuing just one - * read() call, and send them as one CopyData message at one time; - * nmsgs is the number of CopyData messages sent in this XLogSend; - * npages is the number of pages we have determined can be read and - * sent together; startpos is the starting position of reading and - * sending in the first page, startoff is the file offset at which - * it should go and endpos is the end position of reading and - * sending in the last page. We must initialize all of them to - * keep the compiler quiet. + * We gather multiple records together by issuing just one read() of + * a suitable size, and send them as one CopyData message. Repeat + * until we've sent everything we can. */ - while (XLByteLT(sentPtr, SendRqstPtr)) { XLogRecPtr startptr; @@ -631,31 +623,30 @@ XLogSend(StringInfo outMsg) /* * Figure out how much to send in one message. If there's less than * MAX_SEND_SIZE bytes to send, send everything. Otherwise send - * MAX_SEND_SIZE bytes, but round to page boundary for efficiency. + * MAX_SEND_SIZE bytes, but round to page boundary. + * + * The rounding is not only for performance reasons. Walreceiver + * relies on the fact that we never split a WAL record across two + * messages. Since a long WAL record is split at page boundary into + * continuation records, page boundary is alwayssafe cut-off point. + * We also assume that SendRqstPtr never points in the middle of a + * WAL record. */ startptr = sentPtr; endptr = startptr; XLByteAdvance(endptr, MAX_SEND_SIZE); - - /* - * Round down to page boundary. This is not only for performance - * reasons, walreceiver relies on the fact that we never split a WAL - * record across two messages. Since a long WAL record is split at - * page boundary into continuation records, page boundary is always - * safe cut-off point. We also assume that SendRqstPtr never points - * in the middle of a WAL record. - */ + /* round down to page boundary. */ endptr.xrecoff -= (endptr.xrecoff % XLOG_BLCKSZ); - + /* if we went beyond SendRqstPtr, back off */ if (XLByteLT(SendRqstPtr, endptr)) endptr = SendRqstPtr; /* - * OK to read and send the log. + * OK to read and send the slice. * * We don't need to convert the xlogid/xrecoff from host byte order * to network byte order because the both server can be expected to - * have the same byte order. If they have the different order, we + * have the same byte order. If they have different byte order, we * don't reach here. */ pq_sendbytes(outMsg, (char *) &startptr, sizeof(startptr)); @@ -671,7 +662,7 @@ XLogSend(StringInfo outMsg) sentPtr = endptr; /* - * Read the log into the output buffer directly to prevent + * Read the log directly into the output buffer to prevent * extra memcpy calls. */ enlargeStringInfo(outMsg, nbytes); -- GitLab