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Adjust the API for aggregate function calls so that a C-coded function

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can tell whether it is being used as an aggregate or not.  This allows
such a function to avoid re-pallocing a pass-by-reference transition
value; normally it would be unsafe for a function to scribble on an input,
but in the aggregate case it's safe to reuse the old transition value.
Make int8inc() do this.  This gets a useful improvement in the speed of
COUNT(*), at least on narrow tables (it seems to be swamped by I/O when
the table rows are wide).  Per a discussion in early December with
Neil Conway.  I also fixed int_aggregate.c to check this, thereby
turning it into something approaching a supportable technique instead
of being a crude hack.
This commit is contained in:
Tom Lane
2005-03-12 20:25:06 +00:00
parent de004e44e2
commit fa5e44017a
6 changed files with 159 additions and 70 deletions
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49
src/backend/utils/adt/int8.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/int8.c,v 1.57 2004/12/31 22:01:22 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/int8.c,v 1.58 2005/03/12 20:25:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,6 +19,7 @@
#include "funcapi.h"
#include "libpq/pqformat.h"
#include "nodes/nodes.h"
#include "utils/int8.h"
@ -649,17 +650,45 @@ int8mod(PG_FUNCTION_ARGS)
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int8inc(PG_FUNCTION_ARGS)
{
int64 arg = PG_GETARG_INT64(0);
int64 result;
if (fcinfo->context && IsA(fcinfo->context, AggState))
{
/*
* Special case to avoid palloc overhead for COUNT(): when called
* from nodeAgg, we know that the argument is modifiable local
* storage, so just update it in-place.
*
* Note: this assumes int8 is a pass-by-ref type; if we ever support
* pass-by-val int8, this should be ifdef'd out when int8 is
* pass-by-val.
*/
int64 *arg = (int64 *) PG_GETARG_POINTER(0);
int64 result;
result = arg + 1;
/* Overflow check */
if (arg > 0 && result < 0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("bigint out of range")));
result = *arg + 1;
/* Overflow check */
if (result < 0 && *arg > 0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("bigint out of range")));
PG_RETURN_INT64(result);
*arg = result;
PG_RETURN_POINTER(arg);
}
else
{
/* Not called by nodeAgg, so just do it the dumb way */
int64 arg = PG_GETARG_INT64(0);
int64 result;
result = arg + 1;
/* Overflow check */
if (result < 0 && arg > 0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("bigint out of range")));
PG_RETURN_INT64(result);
}
}
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