Neil Conway wrote:
Bruce Momjian wrote:
+ /* + * Return the length of a datum, possibly compressed
+ */
+ Datum
+ pg_column_size(PG_FUNCTION_ARGS)
+ {
+ Datum value = PG_GETARG_DATUM(0);
+ int result;
+ + /* fn_extra stores the fixed column length, or -1 for
varlena. */
+ if (fcinfo->flinfo->fn_extra == NULL) /* first call? */
+ {
+ /* On the first call lookup the datatype of the supplied
argument */
[...]
Is this optimization worth the code complexity?
I didn't performance test it, but the idea of hammering the catalogs for
each value to be processed seemed a bad thing.
+ tp = SearchSysCache(TYPEOID,
+ ObjectIdGetDatum(argtypeid),
+ 0, 0, 0);
+ if (!HeapTupleIsValid(tp))
+ {
+ /* Oid not in pg_type, should never happen. */
+ ereport(ERROR,
+ (errcode(ERRCODE_INTERNAL_ERROR),
+ errmsg("invalid typid: %u", argtypeid)));
+ }
elog(ERROR) is usually used for "can't happen" errors; also, the usual
error message in this scenario is "cache lookup failed [...]". Perhaps
better to use get_typlen() here, anyway.
Ahem,..ah yes, get_typlen()! (ducks)- that is clearly much better!
I have attached a little change to varlena.c that uses it. I left the
ereport as it was, but am not fussed about it either way.
BTW - Bruce, I like the changes, makes the beast more friendly to use!
Best wishes
Mark
Index: src/backend/utils/adt/varlena.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/adt/varlena.c,v
retrieving revision 1.125
diff -c -r1.125 varlena.c
*** src/backend/utils/adt/varlena.c 6 Jul 2005 19:02:52 -0000 1.125
--- src/backend/utils/adt/varlena.c 7 Jul 2005 02:52:50 -0000
***************
*** 28,34 ****
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/pg_locale.h"
- #include "utils/syscache.h"
typedef struct varlena unknown;
--- 28,33 ----
***************
*** 2364,2385 ****
{
/* On the first call lookup the datatype of the supplied
argument */
Oid argtypeid =
get_fn_expr_argtype(fcinfo->flinfo, 0);
! HeapTuple tp;
! int typlen;
! tp = SearchSysCache(TYPEOID,
!
ObjectIdGetDatum(argtypeid),
! 0, 0, 0);
! if (!HeapTupleIsValid(tp))
{
/* Oid not in pg_type, should never happen. */
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
! errmsg("invalid typid: %u",
argtypeid)));
}
!
! typlen = ((Form_pg_type)GETSTRUCT(tp))->typlen;
! ReleaseSysCache(tp);
fcinfo->flinfo->fn_extra =
MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
sizeof(int));
*(int *)fcinfo->flinfo->fn_extra = typlen;
--- 2363,2379 ----
{
/* On the first call lookup the datatype of the supplied
argument */
Oid argtypeid =
get_fn_expr_argtype(fcinfo->flinfo, 0);
! int typlen =
get_typlen(argtypeid);
!
! if (typlen == 0)
{
/* Oid not in pg_type, should never happen. */
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
! errmsg("cache lookup failed for type
%u", argtypeid)));
}
!
fcinfo->flinfo->fn_extra =
MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
sizeof(int));
*(int *)fcinfo->flinfo->fn_extra = typlen;
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