Implement the basic form of UNNEST, ie unnest(anyarray) returns setof

anyelement.  This lacks the WITH ORDINALITY option, as well as the multiple
input arrays option added in the most recent SQL specs.  But it's still a
pretty useful subset of the spec's functionality, and it is enough to
allow obsoleting contrib/intagg.

1 files changed, 105 insertions, 1 deletions

diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
index 9d2b036897b..4580040d697 100644
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.149 2008/11/12 13:09:27 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.150 2008/11/14 00:51:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -4635,3 +4635,107 @@ array_fill_internal(ArrayType *dims, ArrayType *lbs,
 
 	return result;
 }
+
+
+/*
+ * UNNEST
+ */
+Datum
+array_unnest(PG_FUNCTION_ARGS)
+{
+	typedef struct
+	{
+		ArrayType *arr;
+		int		nextelem;
+		int		numelems;
+		char   *elemdataptr;	/* this moves with nextelem */
+		bits8  *arraynullsptr;	/* this does not */
+		int16	elmlen;
+		bool	elmbyval;
+		char	elmalign;
+	} array_unnest_fctx;
+
+	FuncCallContext *funcctx;
+	array_unnest_fctx *fctx;
+	MemoryContext oldcontext;
+
+	/* stuff done only on the first call of the function */
+	if (SRF_IS_FIRSTCALL())
+	{
+		ArrayType  *arr = PG_GETARG_ARRAYTYPE_P(0);
+
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/*
+		 * switch to memory context appropriate for multiple function calls
+		 */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		/* allocate memory for user context */
+		fctx = (array_unnest_fctx *) palloc(sizeof(array_unnest_fctx));
+
+		/*
+		 * Initialize state.  Note we assume that the originally passed
+		 * array will stick around for the whole call series.
+		 */
+		fctx->arr = arr;
+		fctx->nextelem = 0;
+		fctx->numelems = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));
+
+		fctx->elemdataptr = ARR_DATA_PTR(arr);
+		fctx->arraynullsptr = ARR_NULLBITMAP(arr);
+
+		get_typlenbyvalalign(ARR_ELEMTYPE(arr),
+							 &fctx->elmlen,
+							 &fctx->elmbyval,
+							 &fctx->elmalign);
+
+		funcctx->user_fctx = fctx;
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	/* stuff done on every call of the function */
+	funcctx = SRF_PERCALL_SETUP();
+	fctx = funcctx->user_fctx;
+
+	if (fctx->nextelem < fctx->numelems)
+	{
+		int		offset = fctx->nextelem++;
+		Datum	elem;
+
+		/*
+		 * Check for NULL array element
+		 */
+		if (array_get_isnull(fctx->arraynullsptr, offset))
+		{
+			fcinfo->isnull = true;
+			elem = (Datum) 0;
+			/* elemdataptr does not move */
+		}
+		else
+		{
+			/*
+			 * OK, get the element
+			 */
+			char   *ptr = fctx->elemdataptr;
+
+			fcinfo->isnull = false;
+			elem = ArrayCast(ptr, fctx->elmbyval, fctx->elmlen);
+
+			/*
+			 * Advance elemdataptr over it
+			 */
+			ptr = att_addlength_pointer(ptr, fctx->elmlen, ptr);
+			ptr = (char *) att_align_nominal(ptr, fctx->elmalign);
+			fctx->elemdataptr = ptr;
+		}
+
+		SRF_RETURN_NEXT(funcctx, elem);
+	}
+	else
+	{
+		/* do when there is no more left */
+		SRF_RETURN_DONE(funcctx);
+	}
+}