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XLogReader general code cleanup

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Some minor tweaks and comment additions, for cleanliness sake and to
avoid having the upcoming timeline-following patch be polluted with
unrelated cleanup.

Extracted from a larger patch by Craig Ringer, reviewed by Andres
Freund, with some additions by myself.
This commit is contained in:
Alvaro Herrera
2016-03-30 18:56:13 -03:00
parent 50861cd683
commit 3b02ea4f07
5 changed files with 86 additions and 30 deletions
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54
src/backend/access/transam/xlogreader.c
View File

@ -10,9 +10,11 @@
*
* NOTES
* See xlogreader.h for more notes on this facility.
*
* This file is compiled as both front-end and backend code, so it
* may not use ereport, server-defined static variables, etc.
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/transam.h"
@ -192,7 +194,7 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
{
XLogRecord *record;
XLogRecPtr targetPagePtr;
bool randAccess = false;
bool randAccess;
uint32 len,
total_len;
uint32 targetRecOff;
@ -200,6 +202,13 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
bool gotheader;
int readOff;
/*
* randAccess indicates whether to verify the previous-record pointer of
* the record we're reading. We only do this if we're reading
* sequentially, which is what we initially assume.
*/
randAccess = false;
/* reset error state */
*errormsg = NULL;
state->errormsg_buf[0] = '\0';
@ -208,6 +217,7 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
if (RecPtr == InvalidXLogRecPtr)
{
/* No explicit start point; read the record after the one we just read */
RecPtr = state->EndRecPtr;
if (state->ReadRecPtr == InvalidXLogRecPtr)
@ -223,11 +233,13 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
else
{
/*
* Caller supplied a position to start at.
*
* In this case, the passed-in record pointer should already be
* pointing to a valid record starting position.
*/
Assert(XRecOffIsValid(RecPtr));
randAccess = true; /* allow readPageTLI to go backwards too */
randAccess = true;
}
state->currRecPtr = RecPtr;
@ -309,8 +321,10 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
/* XXX: more validation should be done here */
if (total_len < SizeOfXLogRecord)
{
report_invalid_record(state, "invalid record length at %X/%X",
(uint32) (RecPtr >> 32), (uint32) RecPtr);
report_invalid_record(state,
"invalid record length at %X/%X: wanted %lu, got %u",
(uint32) (RecPtr >> 32), (uint32) RecPtr,
SizeOfXLogRecord, total_len);
goto err;
}
gotheader = false;
@ -463,12 +477,10 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
err:
/*
* Invalidate the xlog page we've cached. We might read from a different
* source after failure.
* Invalidate the read state. We might read from a different source after
* failure.
*/
state->readSegNo = 0;
state->readOff = 0;
state->readLen = 0;
XLogReaderInvalReadState(state);
if (state->errormsg_buf[0] != '\0')
*errormsg = state->errormsg_buf;
@ -572,7 +584,7 @@ ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr, int reqLen)
if (!ValidXLogPageHeader(state, pageptr, hdr))
goto err;
/* update cache information */
/* update read state information */
state->readSegNo = targetSegNo;
state->readOff = targetPageOff;
state->readLen = readLen;
@ -580,10 +592,19 @@ ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr, int reqLen)
return readLen;
err:
XLogReaderInvalReadState(state);
return -1;
}
/*
* Invalidate the xlogreader's read state to force a re-read.
*/
void
XLogReaderInvalReadState(XLogReaderState *state)
{
state->readSegNo = 0;
state->readOff = 0;
state->readLen = 0;
return -1;
}
/*
@ -600,8 +621,9 @@ ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
if (record->xl_tot_len < SizeOfXLogRecord)
{
report_invalid_record(state,
"invalid record length at %X/%X",
(uint32) (RecPtr >> 32), (uint32) RecPtr);
"invalid record length at %X/%X: wanted %lu, got %u",
(uint32) (RecPtr >> 32), (uint32) RecPtr,
SizeOfXLogRecord, record->xl_tot_len);
return false;
}
if (record->xl_rmid > RM_MAX_ID)
@ -907,11 +929,9 @@ XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
err:
out:
/* Reset state to what we had before finding the record */
state->readSegNo = 0;
state->readOff = 0;
state->readLen = 0;
state->ReadRecPtr = saved_state.ReadRecPtr;
state->EndRecPtr = saved_state.EndRecPtr;
XLogReaderInvalReadState(state);
return found;
}