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
This commit is contained in:
Simon Riggs
parent
45be99f8cd
commit
422a55a687
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@ -17,7 +17,12 @@
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*/
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#include "postgres.h"
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#include <unistd.h>
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#include "miscadmin.h"
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#include "access/xlog.h"
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#include "access/xlog_internal.h"
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#include "access/xlogutils.h"
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#include "catalog/catalog.h"
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#include "storage/smgr.h"
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@ -631,3 +636,164 @@ XLogTruncateRelation(RelFileNode rnode, ForkNumber forkNum,
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{
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forget_invalid_pages(rnode, forkNum, nblocks);
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}
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/*
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* TODO: This is duplicate code with pg_xlogdump, similar to walsender.c, but
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* we currently don't have the infrastructure (elog!) to share it.
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*/
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static void
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XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count)
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{
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char *p;
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XLogRecPtr recptr;
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Size nbytes;
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static int sendFile = -1;
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static XLogSegNo sendSegNo = 0;
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static uint32 sendOff = 0;
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p = buf;
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recptr = startptr;
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nbytes = count;
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while (nbytes > 0)
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{
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uint32 startoff;
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int segbytes;
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int readbytes;
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startoff = recptr % XLogSegSize;
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if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
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{
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char path[MAXPGPATH];
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/* Switch to another logfile segment */
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if (sendFile >= 0)
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close(sendFile);
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XLByteToSeg(recptr, sendSegNo);
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XLogFilePath(path, tli, sendSegNo);
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sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
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if (sendFile < 0)
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{
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if (errno == ENOENT)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("requested WAL segment %s has already been removed",
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path)));
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else
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not open file \"%s\": %m",
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path)));
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}
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sendOff = 0;
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}
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/* Need to seek in the file? */
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if (sendOff != startoff)
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{
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if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
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{
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char path[MAXPGPATH];
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XLogFilePath(path, tli, sendSegNo);
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not seek in log segment %s to offset %u: %m",
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path, startoff)));
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}
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sendOff = startoff;
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}
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/* How many bytes are within this segment? */
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if (nbytes > (XLogSegSize - startoff))
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segbytes = XLogSegSize - startoff;
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else
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segbytes = nbytes;
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readbytes = read(sendFile, p, segbytes);
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if (readbytes <= 0)
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{
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char path[MAXPGPATH];
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XLogFilePath(path, tli, sendSegNo);
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not read from log segment %s, offset %u, length %lu: %m",
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path, sendOff, (unsigned long) segbytes)));
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}
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/* Update state for read */
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recptr += readbytes;
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sendOff += readbytes;
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nbytes -= readbytes;
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p += readbytes;
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}
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}
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/*
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* read_page callback for reading local xlog files
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*
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* Public because it would likely be very helpful for someone writing another
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* output method outside walsender, e.g. in a bgworker.
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*
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* TODO: The walsender has it's own version of this, but it relies on the
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* walsender's latch being set whenever WAL is flushed. No such infrastructure
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* exists for normal backends, so we have to do a check/sleep/repeat style of
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* loop for now.
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*/
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int
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read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
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int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI)
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{
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XLogRecPtr flushptr,
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loc;
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int count;
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loc = targetPagePtr + reqLen;
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while (1)
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{
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/*
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* TODO: we're going to have to do something more intelligent about
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* timelines on standbys. Use readTimeLineHistory() and
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* tliOfPointInHistory() to get the proper LSN? For now we'll catch
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* that case earlier, but the code and TODO is left in here for when
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* that changes.
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*/
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if (!RecoveryInProgress())
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{
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*pageTLI = ThisTimeLineID;
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flushptr = GetFlushRecPtr();
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}
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else
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flushptr = GetXLogReplayRecPtr(pageTLI);
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if (loc <= flushptr)
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break;
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CHECK_FOR_INTERRUPTS();
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pg_usleep(1000L);
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}
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/* more than one block available */
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if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
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count = XLOG_BLCKSZ;
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/* not enough data there */
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else if (targetPagePtr + reqLen > flushptr)
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return -1;
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/* part of the page available */
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else
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count = flushptr - targetPagePtr;
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XLogRead(cur_page, *pageTLI, targetPagePtr, XLOG_BLCKSZ);
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return count;
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}
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@ -22,6 +22,7 @@
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#include "miscadmin.h"
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#include "access/xlog_internal.h"
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#include "access/xlogutils.h"
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#include "catalog/pg_type.h"
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@ -100,108 +101,6 @@ LogicalOutputWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xi
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p->returned_rows++;
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}
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/*
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* TODO: This is duplicate code with pg_xlogdump, similar to walsender.c, but
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* we currently don't have the infrastructure (elog!) to share it.
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*/
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static void
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XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count)
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{
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char *p;
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XLogRecPtr recptr;
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Size nbytes;
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static int sendFile = -1;
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static XLogSegNo sendSegNo = 0;
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static uint32 sendOff = 0;
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p = buf;
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recptr = startptr;
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nbytes = count;
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while (nbytes > 0)
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{
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uint32 startoff;
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int segbytes;
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int readbytes;
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startoff = recptr % XLogSegSize;
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if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
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{
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char path[MAXPGPATH];
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/* Switch to another logfile segment */
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if (sendFile >= 0)
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close(sendFile);
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XLByteToSeg(recptr, sendSegNo);
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XLogFilePath(path, tli, sendSegNo);
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sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
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if (sendFile < 0)
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{
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if (errno == ENOENT)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("requested WAL segment %s has already been removed",
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path)));
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else
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not open file \"%s\": %m",
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path)));
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}
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sendOff = 0;
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}
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/* Need to seek in the file? */
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if (sendOff != startoff)
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{
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if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
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{
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char path[MAXPGPATH];
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XLogFilePath(path, tli, sendSegNo);
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not seek in log segment %s to offset %u: %m",
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path, startoff)));
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}
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sendOff = startoff;
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}
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/* How many bytes are within this segment? */
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if (nbytes > (XLogSegSize - startoff))
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segbytes = XLogSegSize - startoff;
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else
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segbytes = nbytes;
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readbytes = read(sendFile, p, segbytes);
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if (readbytes <= 0)
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{
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char path[MAXPGPATH];
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XLogFilePath(path, tli, sendSegNo);
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not read from log segment %s, offset %u, length %lu: %m",
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path, sendOff, (unsigned long) segbytes)));
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}
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/* Update state for read */
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recptr += readbytes;
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sendOff += readbytes;
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nbytes -= readbytes;
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p += readbytes;
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}
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}
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static void
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check_permissions(void)
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{
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@ -211,63 +110,12 @@ check_permissions(void)
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(errmsg("must be superuser or replication role to use replication slots"))));
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}
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/*
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* read_page callback for logical decoding contexts.
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*
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* Public because it would likely be very helpful for someone writing another
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* output method outside walsender, e.g. in a bgworker.
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*
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* TODO: The walsender has it's own version of this, but it relies on the
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* walsender's latch being set whenever WAL is flushed. No such infrastructure
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* exists for normal backends, so we have to do a check/sleep/repeat style of
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* loop for now.
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*/
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int
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logical_read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
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int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI)
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{
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XLogRecPtr flushptr,
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loc;
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int count;
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loc = targetPagePtr + reqLen;
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while (1)
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{
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/*
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* TODO: we're going to have to do something more intelligent about
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* timelines on standbys. Use readTimeLineHistory() and
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* tliOfPointInHistory() to get the proper LSN? For now we'll catch
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* that case earlier, but the code and TODO is left in here for when
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* that changes.
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*/
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if (!RecoveryInProgress())
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{
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*pageTLI = ThisTimeLineID;
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flushptr = GetFlushRecPtr();
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}
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else
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flushptr = GetXLogReplayRecPtr(pageTLI);
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if (loc <= flushptr)
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break;
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CHECK_FOR_INTERRUPTS();
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pg_usleep(1000L);
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}
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/* more than one block available */
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if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
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count = XLOG_BLCKSZ;
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/* not enough data there */
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else if (targetPagePtr + reqLen > flushptr)
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return -1;
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/* part of the page available */
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else
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count = flushptr - targetPagePtr;
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XLogRead(cur_page, *pageTLI, targetPagePtr, XLOG_BLCKSZ);
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return count;
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return read_local_xlog_page(state, targetPagePtr, reqLen,
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targetRecPtr, cur_page, pageTLI);
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}
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/*
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@ -47,4 +47,7 @@ extern Buffer XLogReadBufferExtended(RelFileNode rnode, ForkNumber forknum,
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extern Relation CreateFakeRelcacheEntry(RelFileNode rnode);
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extern void FreeFakeRelcacheEntry(Relation fakerel);
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extern int read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
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int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI);
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#endif
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