I've been taking a look at this as well and came up with a slightly
different approach. The attached patch is intended to go in core (not
contrib) and uses some array-construction facilities that already
exist in core. I'm not sure which approach is better, so I'll throw
this out there with yours for input...
...Robert
Index: src/backend/utils/adt/array_userfuncs.c
===
RCS file: /projects/cvsroot/pgsql/src/backend/utils/adt/array_userfuncs.c,v
retrieving revision 1.23
diff -c -r1.23 array_userfuncs.c
*** src/backend/utils/adt/array_userfuncs.c 1 Jan 2008 19:45:52 - 1.23
--- src/backend/utils/adt/array_userfuncs.c 16 Oct 2008 02:22:03 -
***
*** 12,17
--- 12,18
*/
#include "postgres.h"
+ #include "nodes/execnodes.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
***
*** 465,467
--- 466,510
return construct_md_array(dvalues, NULL, ndims, dims, lbs, element_type,
typlen, typbyval, typalign);
}
+
+ /*
+ * aggregate values into an array
+ */
+ Datum
+ array_accum_trans(PG_FUNCTION_ARGS)
+ {
+ ArrayBuildState *ain, *aout;
+ MemoryContext *mctx;
+ Oid arg1_typeid = get_fn_expr_argtype(fcinfo->flinfo, 1);
+
+ if (!(fcinfo->context && IsA(fcinfo->context, AggState)))
+ ereport(ERROR,
+ (errmsg("array_accum_trans may only be used as an aggregate")));
+ mctx = ((AggState *) fcinfo->context)->aggcontext;
+ if (arg1_typeid == InvalidOid)
+ ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("could not determine input data type")));
+
+ if (PG_ARGISNULL(0))
+ ain = NULL;
+ else
+ ain = PG_GETARG_POINTER(0);
+
+ aout = accumArrayResult(ain, PG_GETARG_DATUM(1), PG_ARGISNULL(1),
+ arg1_typeid, mctx);
+ PG_RETURN_POINTER(aout);
+ }
+
+ /*
+ * finalize accumulated array
+ */
+ Datum
+ array_accum_final(PG_FUNCTION_ARGS)
+ {
+ ArrayBuildState *astate;
+
+ if (PG_ARGISNULL(0))
+ PG_RETURN_NULL();
+ astate = (ArrayBuildState *) PG_GETARG_POINTER(0);
+ PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));
+ }
Index: src/include/catalog/pg_aggregate.h
===
RCS file: /projects/cvsroot/pgsql/src/include/catalog/pg_aggregate.h,v
retrieving revision 1.66
diff -c -r1.66 pg_aggregate.h
*** src/include/catalog/pg_aggregate.h 27 Mar 2008 03:57:34 - 1.66
--- src/include/catalog/pg_aggregate.h 16 Oct 2008 02:22:04 -
***
*** 220,225
--- 220,228
/* xml */
DATA(insert ( 2901 xmlconcat2 - 0 142 _null_ ));
+ /* array */
+ DATA(insert ( 2335 array_accum_trans array_accum_final 0 2281 _null_ ));
+
/*
* prototypes for functions in pg_aggregate.c
*/
Index: src/include/catalog/pg_proc.h
===
RCS file: /projects/cvsroot/pgsql/src/include/catalog/pg_proc.h,v
retrieving revision 1.520
diff -c -r1.520 pg_proc.h
*** src/include/catalog/pg_proc.h 14 Oct 2008 17:12:33 - 1.520
--- src/include/catalog/pg_proc.h 16 Oct 2008 02:22:13 -
***
*** 1017,1022
--- 1017,1024
DESCR("array constructor with value");
DATA(insert OID = 1286 ( array_fill PGNSP PGUID 12 1 0 0 f f f f i 3 2277 "2283 1007 1007" _null_ _null_ _null_ array_fill_with_lower_bounds _null_ _null_ _null_ ));
DESCR("array constructor with value");
+ DATA(insert OID = 2333 ( array_accum_trans PGNSP PGUID 12 1 0 0 f f f f i 2 2281 "2281 2283" _null_ _null_ _null_ array_accum_trans _null_ _null_ _null_ ));
+ DATA(insert OID = 2334 ( array_accum_final PGNSP PGUID 12 1 0 0 f f f f i 1 2277 "2281" _null_ _null_ _null_ array_accum_final _null_ _null_ _null_ ));
DATA(insert OID = 760 ( smgrin PGNSP PGUID 12 1 0 0 f f t f s 1 210 "2275" _null_ _null_ _null_ smgrin _null_ _null_ _null_ ));
DESCR("I/O");
DATA(insert OID = 761 ( smgrout PGNSP PGUID 12 1 0 0 f f t f s 1 2275 "210" _null_ _null_ _null_ smgrout _null_ _null_ _null_ ));
***
*** 3439,3444
--- 3441,3448
DATA(insert OID = 2829 ( corrPGNSP PGUID 12 1 0 0 t f f f i 2 701 "701 701" _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
DESCR("correlation coefficient");
+ DATA(insert OID = 2335 ( array_accum PGNSP PGUID 12 1 0 0 t f f f i 1 2277 "2283" _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
+
DATA(insert OID = 2160 ( text_pattern_lt PGNSP PGUID 12 1 0 0 f f t f i 2 16 "25 25" _null_ _null_ _null_ text_pattern_lt _null_ _null_ _null_ ));
DATA(insert OID = 2161 ( text_pattern_le PGNSP PGUID 12 1 0 0 f f t f i 2 16 "25 25" _null_ _null_ _null_ text_pattern_le _null_ _null_ _null_ ));
DATA(insert OID = 2163 ( text_pattern_ge PGNSP PGUID 12 1 0 0 f f t f i 2 16 "25 25" _null_ _null_ _null_ text_pattern_ge _null_ _null_ _null_ ));
Index: src/include/utils/array.h
===
