Re: [HACKERS] Forcing current WAL file to be archived

On Wed, 2006-08-16 at 11:45 -0400, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > We want a single row output, with two columns, yes?
> > Presumably:
> > xlogfilename TEXT
> > offset INTEGER
>
> Sounds right to me. int4 should be wide enough for practical xlog
> segment sizes.

Wise one: what should my pg_proc look like?

I'm the lucky man to break the "_null_ _null_ _null_" rule...

I've tried

DATA(insert OID = 2850 ( pg_xlogfile_name_offset PGNSP PGUID 12 f f t f
i 1 2249 "25" "25 25 23" "i o o" _null_ pg_xlogfile_name_offset -
_null_ ));

but my initdb fails with

selecting default shared_buffers/max_fsm_pages ... 20000kB/1000000
creating configuration files ... ok
creating template1 database in a/base/1 ... FATAL: cache lookup failed
for type 26
child process exited with exit code 1
initdb: removing data directory "a"

Thinking this might be an 0-referenced array issue, I also tried "24 24
22" in the above, but that bombs with the same error.

Currently, if I just leave it as it is, then initdb runs but then
hangs/bombs when you invokle the function (as you might expect).

As far as I can tell, the function isn't ever called correctly without
this... copied here for info.

/*
* Compute an xlog file name and decimal byte offset given a WAL
location,
* such as is returned by pg_stop_backup() or pg_xlog_switch().
*
* Note that a location exactly at a segment boundary is taken to be in
* the previous segment. This is usually the right thing, since the
* expected usage is to determine which xlog file(s) are ready to
archive.
*/
Datum
pg_xlogfile_name_offset(PG_FUNCTION_ARGS)
{
text *location = PG_GETARG_TEXT_P(0);
char *locationstr;
unsigned int uxlogid;
unsigned int uxrecoff;
uint32 xlogid;
uint32 xlogseg;
uint32 xrecoff;
XLogRecPtr locationpoint;
char xlogfilename[MAXFNAMELEN];
TupleDesc returnTupleDesc;
Datum values[2];
bool isnull[2];
HeapTuple returnHeapTuple;
Datum result;

/*
* Read input and parse
*/
locationstr = DatumGetCString(DirectFunctionCall1(textout,
PointerGetDatum(location)));

if (sscanf(locationstr, "%X/%X", &uxlogid, &uxrecoff) != 2)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("could not parse xlog location \"%s\"",
locationstr)));

locationpoint.xlogid = uxlogid;
locationpoint.xrecoff = uxrecoff;

/* Construct a tuple descriptor for the result rows. */
returnTupleDesc = CreateTemplateTupleDesc(2, false);
TupleDescInitEntry(returnTupleDesc, (AttrNumber) 1, "xlogfilename",
TEXTOID, -1, 0);
TupleDescInitEntry(returnTupleDesc, (AttrNumber) 2, "offset",
INT4OID, -1, 0);

returnTupleDesc = BlessTupleDesc(returnTupleDesc);

/*
* xlogfilename
*/
XLByteToPrevSeg(locationpoint, xlogid, xlogseg);

XLogFileName(xlogfilename, ThisTimeLineID, xlogid, xlogseg);

values[0] = PointerGetDatum(xlogfilename);
isnull[0] = false;

/*
* offset
*/
xrecoff = locationpoint.xrecoff - xlogseg * XLogSegSize;

values[1] = UInt32GetDatum(xrecoff);
isnull[1] = false;

/*
* Tuple jam: Having first prepared your Datums, then squash
together
*/
returnHeapTuple = heap_form_tuple(returnTupleDesc, values, isnull);

result = HeapTupleGetDatum(returnHeapTuple);

PG_RETURN_DATUM(result);
}

--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com