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Don't waste the last segment of each 4GB logical log file.

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The comments claimed that wasting the last segment made it easier to do
calculations with XLogRecPtrs, because you don't have problems representing
last-byte-position-plus-1 that way. In my experience, however, it only made
things more complicated, because the there was two ways to represent the
boundary at the beginning of a logical log file: logid = n+1 and xrecoff = 0,
or as xlogid = n and xrecoff = 4GB - XLOG_SEG_SIZE. Some functions were
picky about which representation was used.

Also, use a 64-bit segment number instead of the log/seg combination, to
point to a certain WAL segment. We assume that all platforms have a working
64-bit integer type nowadays.

This is an incompatible change in WAL format, so bumping WAL version number.
This commit is contained in:
Heikki Linnakangas
2012-06-24 18:06:38 +03:00
parent 47c7365e79
commit dfda6ebaec
12 changed files with 413 additions and 554 deletions
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48
src/backend/access/transam/xlogfuncs.c
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@ -271,8 +271,7 @@ pg_xlogfile_name_offset(PG_FUNCTION_ARGS)
char *locationstr;
unsigned int uxlogid;
unsigned int uxrecoff;
uint32 xlogid;
uint32 xlogseg;
XLogSegNo xlogsegno;
uint32 xrecoff;
XLogRecPtr locationpoint;
char xlogfilename[MAXFNAMELEN];
@ -319,8 +318,8 @@ pg_xlogfile_name_offset(PG_FUNCTION_ARGS)
/*
* xlogfilename
*/
XLByteToPrevSeg(locationpoint, xlogid, xlogseg);
XLogFileName(xlogfilename, ThisTimeLineID, xlogid, xlogseg);
XLByteToPrevSeg(locationpoint, xlogsegno);
XLogFileName(xlogfilename, ThisTimeLineID, xlogsegno);
values[0] = CStringGetTextDatum(xlogfilename);
isnull[0] = false;
@ -328,7 +327,7 @@ pg_xlogfile_name_offset(PG_FUNCTION_ARGS)
/*
* offset
*/
xrecoff = locationpoint.xrecoff - xlogseg * XLogSegSize;
xrecoff = locationpoint.xrecoff % XLogSegSize;
values[1] = UInt32GetDatum(xrecoff);
isnull[1] = false;
@ -354,8 +353,7 @@ pg_xlogfile_name(PG_FUNCTION_ARGS)
char *locationstr;
unsigned int uxlogid;
unsigned int uxrecoff;
uint32 xlogid;
uint32 xlogseg;
XLogSegNo xlogsegno;
XLogRecPtr locationpoint;
char xlogfilename[MAXFNAMELEN];
@ -378,8 +376,8 @@ pg_xlogfile_name(PG_FUNCTION_ARGS)
locationpoint.xlogid = uxlogid;
locationpoint.xrecoff = uxrecoff;
XLByteToPrevSeg(locationpoint, xlogid, xlogseg);
XLogFileName(xlogfilename, ThisTimeLineID, xlogid, xlogseg);
XLByteToPrevSeg(locationpoint, xlogsegno);
XLogFileName(xlogfilename, ThisTimeLineID, xlogsegno);
PG_RETURN_TEXT_P(cstring_to_text(xlogfilename));
}
@ -514,6 +512,8 @@ pg_xlog_location_diff(PG_FUNCTION_ARGS)
XLogRecPtr loc1,
loc2;
Numeric result;
uint64 bytes1,
bytes2;
/*
* Read and parse input
@ -533,33 +533,17 @@ pg_xlog_location_diff(PG_FUNCTION_ARGS)
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("could not parse transaction log location \"%s\"", str2)));
/*
* Sanity check
*/
if (loc1.xrecoff > XLogFileSize)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("xrecoff \"%X\" is out of valid range, 0..%X", loc1.xrecoff, XLogFileSize)));
if (loc2.xrecoff > XLogFileSize)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("xrecoff \"%X\" is out of valid range, 0..%X", loc2.xrecoff, XLogFileSize)));
bytes1 = (((uint64)loc1.xlogid) << 32L) + loc1.xrecoff;
bytes2 = (((uint64)loc2.xlogid) << 32L) + loc2.xrecoff;
/*
* result = XLogFileSize * (xlogid1 - xlogid2) + xrecoff1 - xrecoff2
* result = bytes1 - bytes2.
*
* XXX: this won't handle values higher than 2^63 correctly.
*/
result = DatumGetNumeric(DirectFunctionCall2(numeric_sub,
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) loc1.xlogid)),
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) loc2.xlogid))));
result = DatumGetNumeric(DirectFunctionCall2(numeric_mul,
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) XLogFileSize)),
NumericGetDatum(result)));
result = DatumGetNumeric(DirectFunctionCall2(numeric_add,
NumericGetDatum(result),
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) loc1.xrecoff))));
result = DatumGetNumeric(DirectFunctionCall2(numeric_sub,
NumericGetDatum(result),
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) loc2.xrecoff))));
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) bytes1)),
DirectFunctionCall1(int8_numeric, Int64GetDatum((int64) bytes2))));
PG_RETURN_NUMERIC(result);
}