On 23.10.2018 0:53, Heikki Linnakangas wrote:
I'd expect the decompression to read from the on-disk buffer, and unpack
to readRecordBuf, I still don't see a need to copy the packed record to
readRecordBuf. If there is a need for that, though, the patch that
implements the packing or compression can add the memcpy() where it
needs it.
I agree with it. Eventually, placement of the WAL-record can be defined
by comparison the record, readBuf and readRecordBuf pointers.
In attachment new version of the patch.
--
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
>From 36fd35dc75658f471efbc64fe2a3f204f0aa27e4 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepik...@postgrespro.ru>
Date: Tue, 23 Oct 2018 10:17:55 +0500
Subject: [PATCH] WAL-record-buffer-pointer-fix
---
src/backend/access/transam/xlogreader.c | 27 ++++++++++++-------------
1 file changed, 13 insertions(+), 14 deletions(-)
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 0768ca7822..c5e019bf77 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -353,19 +353,6 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
gotheader = false;
}
- /*
- * Enlarge readRecordBuf as needed.
- */
- if (total_len > state->readRecordBufSize &&
- !allocate_recordbuf(state, total_len))
- {
- /* We treat this as a "bogus data" condition */
- report_invalid_record(state, "record length %u at %X/%X too long",
- total_len,
- (uint32) (RecPtr >> 32), (uint32) RecPtr);
- goto err;
- }
-
len = XLOG_BLCKSZ - RecPtr % XLOG_BLCKSZ;
if (total_len > len)
{
@@ -375,6 +362,19 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
char *buffer;
uint32 gotlen;
+ /*
+ * Enlarge readRecordBuf as needed.
+ */
+ if (total_len > state->readRecordBufSize &&
+ !allocate_recordbuf(state, total_len))
+ {
+ /* We treat this as a "bogus data" condition */
+ report_invalid_record(state, "record length %u at %X/%X too long",
+ total_len,
+ (uint32) (RecPtr >> 32), (uint32) RecPtr);
+ goto err;
+ }
+
/* Copy the first fragment of the record from the first page. */
memcpy(state->readRecordBuf,
state->readBuf + RecPtr % XLOG_BLCKSZ, len);
@@ -479,7 +479,6 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
state->EndRecPtr = RecPtr + MAXALIGN(total_len);
state->ReadRecPtr = RecPtr;
- memcpy(state->readRecordBuf, record, total_len);
}
/*
--
2.17.1
