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Remove read_page callback from XLogReader.

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Previously, the XLogReader module would fetch new input data using a
callback function.  Redesign the interface so that it tells the caller
to insert more data with a special return value instead.  This API suits
later patches for prefetching, encryption and maybe other future
projects that would otherwise require continually extending the callback
interface.

As incidental cleanup work, move global variables readOff, readLen and
readSegNo inside XlogReaderState.

Author: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Author: Heikki Linnakangas <hlinnaka@iki.fi> (parts of earlier version)
Reviewed-by: Antonin Houska <ah@cybertec.at>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Reviewed-by: Takashi Menjo <takashi.menjo@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/20190418.210257.43726183.horiguchi.kyotaro%40lab.ntt.co.jp
This commit is contained in:
Thomas Munro
2021-04-08 23:03:23 +12:00
parent 5ac9c43073
commit 323cbe7c7d
13 changed files with 955 additions and 702 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
src/backend/replication/walsender.c
View File

@@ -580,10 +580,7 @@ StartReplication(StartReplicationCmd *cmd)
/* create xlogreader for physical replication */
xlogreader =
XLogReaderAllocate(wal_segment_size, NULL,
XL_ROUTINE(.segment_open = WalSndSegmentOpen,
.segment_close = wal_segment_close),
NULL);
XLogReaderAllocate(wal_segment_size, NULL, wal_segment_close);
if (!xlogreader)
ereport(ERROR,
@@ -806,10 +803,12 @@ StartReplication(StartReplicationCmd *cmd)
* which has to do a plain sleep/busy loop, because the walsender's latch gets
* set every time WAL is flushed.
*/
static int
logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen,
XLogRecPtr targetRecPtr, char *cur_page)
static bool
logical_read_xlog_page(XLogReaderState *state)
{
XLogRecPtr targetPagePtr = state->readPagePtr;
int reqLen = state->reqLen;
char *cur_page = state->readBuf;
XLogRecPtr flushptr;
int count;
WALReadError errinfo;
@@ -826,7 +825,10 @@ logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int req
/* fail if not (implies we are going to shut down) */
if (flushptr < targetPagePtr + reqLen)
return -1;
{
XLogReaderSetInputData(state, -1);
return false;
}
if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
count = XLOG_BLCKSZ; /* more than one block available */
@@ -834,7 +836,7 @@ logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int req
count = flushptr - targetPagePtr; /* part of the page available */
/* now actually read the data, we know it's there */
if (!WALRead(state,
if (!WALRead(state, WalSndSegmentOpen, wal_segment_close,
cur_page,
targetPagePtr,
XLOG_BLCKSZ,
@@ -854,7 +856,8 @@ logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int req
XLByteToSeg(targetPagePtr, segno, state->segcxt.ws_segsize);
CheckXLogRemoved(segno, state->seg.ws_tli);
return count;
XLogReaderSetInputData(state, count);
return true;
}
/*
@@ -1007,9 +1010,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
ctx = CreateInitDecodingContext(cmd->plugin, NIL, need_full_snapshot,
InvalidXLogRecPtr,
XL_ROUTINE(.page_read = logical_read_xlog_page,
.segment_open = WalSndSegmentOpen,
.segment_close = wal_segment_close),
logical_read_xlog_page,
wal_segment_close,
WalSndPrepareWrite, WalSndWriteData,
WalSndUpdateProgress);
@@ -1167,9 +1169,8 @@ StartLogicalReplication(StartReplicationCmd *cmd)
*/
logical_decoding_ctx =
CreateDecodingContext(cmd->startpoint, cmd->options, false,
XL_ROUTINE(.page_read = logical_read_xlog_page,
.segment_open = WalSndSegmentOpen,
.segment_close = wal_segment_close),
logical_read_xlog_page,
wal_segment_close,
WalSndPrepareWrite, WalSndWriteData,
WalSndUpdateProgress);
xlogreader = logical_decoding_ctx->reader;
@@ -2745,7 +2746,7 @@ XLogSendPhysical(void)
enlargeStringInfo(&output_message, nbytes);
retry:
if (!WALRead(xlogreader,
if (!WALRead(xlogreader, WalSndSegmentOpen, wal_segment_close,
&output_message.data[output_message.len],
startptr,
nbytes,
@@ -2843,7 +2844,12 @@ XLogSendLogical(void)
*/
WalSndCaughtUp = false;
record = XLogReadRecord(logical_decoding_ctx->reader, &errm);
while (XLogReadRecord(logical_decoding_ctx->reader, &record, &errm) ==
XLREAD_NEED_DATA)
{
if (!logical_decoding_ctx->page_read(logical_decoding_ctx->reader))
break;
}
/* xlog record was invalid */
if (errm != NULL)