Skip to content

Commit 422a55a

Browse files
simonat2ndQuadrantsimonat2ndQuadrant
committed
Refactor to create generic WAL page read callback
Previously we didn’t have a generic WAL page read callback function, surprisingly. Logical decoding has logical_read_local_xlog_page(), which was actually generic, so move that to xlogfunc.c and rename to read_local_xlog_page(). Maintain logical_read_local_xlog_page() so existing callers still work. As requested by Michael Paquier, Alvaro Herrera and Andres Freund
1 parent 45be99f commit 422a55a

File tree

3 files changed

+172
-155
lines changed

3 files changed

+172
-155
lines changed

‎src/backend/access/transam/xlogutils.c

Lines changed: 166 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -17,7 +17,12 @@
1717
*/
1818
#include "postgres.h"
1919

20+
#include <unistd.h>
21+
22+
#include "miscadmin.h"
23+
2024
#include "access/xlog.h"
25+
#include "access/xlog_internal.h"
2126
#include "access/xlogutils.h"
2227
#include "catalog/catalog.h"
2328
#include "storage/smgr.h"
@@ -631,3 +636,164 @@ XLogTruncateRelation(RelFileNode rnode, ForkNumber forkNum,
631636
{
632637
forget_invalid_pages(rnode, forkNum, nblocks);
633638
}
639+
640+
/*
641+
* TODO: This is duplicate code with pg_xlogdump, similar to walsender.c, but
642+
* we currently don't have the infrastructure (elog!) to share it.
643+
*/
644+
static void
645+
XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count)
646+
{
647+
char *p;
648+
XLogRecPtr recptr;
649+
Size nbytes;
650+
651+
static int sendFile = -1;
652+
static XLogSegNo sendSegNo = 0;
653+
static uint32 sendOff = 0;
654+
655+
p = buf;
656+
recptr = startptr;
657+
nbytes = count;
658+
659+
while (nbytes > 0)
660+
{
661+
uint32 startoff;
662+
int segbytes;
663+
int readbytes;
664+
665+
startoff = recptr % XLogSegSize;
666+
667+
if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
668+
{
669+
char path[MAXPGPATH];
670+
671+
/* Switch to another logfile segment */
672+
if (sendFile >= 0)
673+
close(sendFile);
674+
675+
XLByteToSeg(recptr, sendSegNo);
676+
677+
XLogFilePath(path, tli, sendSegNo);
678+
679+
sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
680+
681+
if (sendFile < 0)
682+
{
683+
if (errno == ENOENT)
684+
ereport(ERROR,
685+
(errcode_for_file_access(),
686+
errmsg("requested WAL segment %s has already been removed",
687+
path)));
688+
else
689+
ereport(ERROR,
690+
(errcode_for_file_access(),
691+
errmsg("could not open file \"%s\": %m",
692+
path)));
693+
}
694+
sendOff = 0;
695+
}
696+
697+
/* Need to seek in the file? */
698+
if (sendOff != startoff)
699+
{
700+
if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
701+
{
702+
char path[MAXPGPATH];
703+
704+
XLogFilePath(path, tli, sendSegNo);
705+
706+
ereport(ERROR,
707+
(errcode_for_file_access(),
708+
errmsg("could not seek in log segment %s to offset %u: %m",
709+
path, startoff)));
710+
}
711+
sendOff = startoff;
712+
}
713+
714+
/* How many bytes are within this segment? */
715+
if (nbytes > (XLogSegSize - startoff))
716+
segbytes = XLogSegSize - startoff;
717+
else
718+
segbytes = nbytes;
719+
720+
readbytes = read(sendFile, p, segbytes);
721+
if (readbytes <= 0)
722+
{
723+
char path[MAXPGPATH];
724+
725+
XLogFilePath(path, tli, sendSegNo);
726+
727+
ereport(ERROR,
728+
(errcode_for_file_access(),
729+
errmsg("could not read from log segment %s, offset %u, length %lu: %m",
730+
path, sendOff, (unsigned long) segbytes)));
731+
}
732+
733+
/* Update state for read */
734+
recptr += readbytes;
735+
736+
sendOff += readbytes;
737+
nbytes -= readbytes;
738+
p += readbytes;
739+
}
740+
}
741+
742+
/*
743+
* read_page callback for reading local xlog files
744+
*
745+
* Public because it would likely be very helpful for someone writing another
746+
* output method outside walsender, e.g. in a bgworker.
747+
*
748+
* TODO: The walsender has it's own version of this, but it relies on the
749+
* walsender's latch being set whenever WAL is flushed. No such infrastructure
750+
* exists for normal backends, so we have to do a check/sleep/repeat style of
751+
* loop for now.
752+
*/
753+
int
754+
read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
755+
int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI)
756+
{
757+
XLogRecPtr flushptr,
758+
loc;
759+
int count;
760+
761+
loc = targetPagePtr + reqLen;
762+
while (1)
763+
{
764+
/*
765+
* TODO: we're going to have to do something more intelligent about
766+
* timelines on standbys. Use readTimeLineHistory() and
767+
* tliOfPointInHistory() to get the proper LSN? For now we'll catch
768+
* that case earlier, but the code and TODO is left in here for when
769+
* that changes.
770+
*/
771+
if (!RecoveryInProgress())
772+
{
773+
*pageTLI = ThisTimeLineID;
774+
flushptr = GetFlushRecPtr();
775+
}
776+
else
777+
flushptr = GetXLogReplayRecPtr(pageTLI);
778+
779+
if (loc <= flushptr)
780+
break;
781+
782+
CHECK_FOR_INTERRUPTS();
783+
pg_usleep(1000L);
784+
}
785+
786+
/* more than one block available */
787+
if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
788+
count = XLOG_BLCKSZ;
789+
/* not enough data there */
790+
else if (targetPagePtr + reqLen > flushptr)
791+
return -1;
792+
/* part of the page available */
793+
else
794+
count = flushptr - targetPagePtr;
795+
796+
XLogRead(cur_page, *pageTLI, targetPagePtr, XLOG_BLCKSZ);
797+
798+
return count;
799+
}

‎src/backend/replication/logical/logicalfuncs.c

Lines changed: 3 additions & 155 deletions
Original file line numberDiff line numberDiff line change
@@ -22,6 +22,7 @@
2222
#include "miscadmin.h"
2323

2424
#include "access/xlog_internal.h"
25+
#include "access/xlogutils.h"
2526

2627
#include "catalog/pg_type.h"
2728

@@ -100,108 +101,6 @@ LogicalOutputWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xi
100101
p->returned_rows++;
101102
}
102103

103-
/*
104-
* TODO: This is duplicate code with pg_xlogdump, similar to walsender.c, but
105-
* we currently don't have the infrastructure (elog!) to share it.
106-
*/
107-
static void
108-
XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count)
109-
{
110-
char *p;
111-
XLogRecPtr recptr;
112-
Size nbytes;
113-
114-
static int sendFile = -1;
115-
static XLogSegNo sendSegNo = 0;
116-
static uint32 sendOff = 0;
117-
118-
p = buf;
119-
recptr = startptr;
120-
nbytes = count;
121-
122-
while (nbytes > 0)
123-
{
124-
uint32 startoff;
125-
int segbytes;
126-
int readbytes;
127-
128-
startoff = recptr % XLogSegSize;
129-
130-
if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
131-
{
132-
char path[MAXPGPATH];
133-
134-
/* Switch to another logfile segment */
135-
if (sendFile >= 0)
136-
close(sendFile);
137-
138-
XLByteToSeg(recptr, sendSegNo);
139-
140-
XLogFilePath(path, tli, sendSegNo);
141-
142-
sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
143-
144-
if (sendFile < 0)
145-
{
146-
if (errno == ENOENT)
147-
ereport(ERROR,
148-
(errcode_for_file_access(),
149-
errmsg("requested WAL segment %s has already been removed",
150-
path)));
151-
else
152-
ereport(ERROR,
153-
(errcode_for_file_access(),
154-
errmsg("could not open file \"%s\": %m",
155-
path)));
156-
}
157-
sendOff = 0;
158-
}
159-
160-
/* Need to seek in the file? */
161-
if (sendOff != startoff)
162-
{
163-
if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
164-
{
165-
char path[MAXPGPATH];
166-
167-
XLogFilePath(path, tli, sendSegNo);
168-
169-
ereport(ERROR,
170-
(errcode_for_file_access(),
171-
errmsg("could not seek in log segment %s to offset %u: %m",
172-
path, startoff)));
173-
}
174-
sendOff = startoff;
175-
}
176-
177-
/* How many bytes are within this segment? */
178-
if (nbytes > (XLogSegSize - startoff))
179-
segbytes = XLogSegSize - startoff;
180-
else
181-
segbytes = nbytes;
182-
183-
readbytes = read(sendFile, p, segbytes);
184-
if (readbytes <= 0)
185-
{
186-
char path[MAXPGPATH];
187-
188-
XLogFilePath(path, tli, sendSegNo);
189-
190-
ereport(ERROR,
191-
(errcode_for_file_access(),
192-
errmsg("could not read from log segment %s, offset %u, length %lu: %m",
193-
path, sendOff, (unsigned long) segbytes)));
194-
}
195-
196-
/* Update state for read */
197-
recptr += readbytes;
198-
199-
sendOff += readbytes;
200-
nbytes -= readbytes;
201-
p += readbytes;
202-
}
203-
}
204-
205104
static void
206105
check_permissions(void)
207106
{
@@ -211,63 +110,12 @@ check_permissions(void)
211110
(errmsg("must be superuser or replication role to use replication slots"))));
212111
}
213112

214-
/*
215-
* read_page callback for logical decoding contexts.
216-
*
217-
* Public because it would likely be very helpful for someone writing another
218-
* output method outside walsender, e.g. in a bgworker.
219-
*
220-
* TODO: The walsender has it's own version of this, but it relies on the
221-
* walsender's latch being set whenever WAL is flushed. No such infrastructure
222-
* exists for normal backends, so we have to do a check/sleep/repeat style of
223-
* loop for now.
224-
*/
225113
int
226114
logical_read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
227115
int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI)
228116
{
229-
XLogRecPtr flushptr,
230-
loc;
231-
int count;
232-
233-
loc = targetPagePtr + reqLen;
234-
while (1)
235-
{
236-
/*
237-
* TODO: we're going to have to do something more intelligent about
238-
* timelines on standbys. Use readTimeLineHistory() and
239-
* tliOfPointInHistory() to get the proper LSN? For now we'll catch
240-
* that case earlier, but the code and TODO is left in here for when
241-
* that changes.
242-
*/
243-
if (!RecoveryInProgress())
244-
{
245-
*pageTLI = ThisTimeLineID;
246-
flushptr = GetFlushRecPtr();
247-
}
248-
else
249-
flushptr = GetXLogReplayRecPtr(pageTLI);
250-
251-
if (loc <= flushptr)
252-
break;
253-
254-
CHECK_FOR_INTERRUPTS();
255-
pg_usleep(1000L);
256-
}
257-
258-
/* more than one block available */
259-
if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
260-
count = XLOG_BLCKSZ;
261-
/* not enough data there */
262-
else if (targetPagePtr + reqLen > flushptr)
263-
return -1;
264-
/* part of the page available */
265-
else
266-
count = flushptr - targetPagePtr;
267-
268-
XLogRead(cur_page, *pageTLI, targetPagePtr, XLOG_BLCKSZ);
269-
270-
return count;
117+
return read_local_xlog_page(state, targetPagePtr, reqLen,
118+
targetRecPtr, cur_page, pageTLI);
271119
}
272120

273121
/*

‎src/include/access/xlogutils.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -47,4 +47,7 @@ extern Buffer XLogReadBufferExtended(RelFileNode rnode, ForkNumber forknum,
4747
extern Relation CreateFakeRelcacheEntry(RelFileNode rnode);
4848
extern void FreeFakeRelcacheEntry(Relation fakerel);
4949

50+
extern int read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
51+
int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI);
52+
5053
#endif

0 commit comments

Comments
 (0)
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy