Create AVG() aggregates for int8 and NUMERIC which do not compute X^2,

as a performance enhancement.

Mark Kirkwood

src/backend/utils/adt/numeric.c

@@ -14,7 +14,7 @@
  * Copyright (c) 1998-2007, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.99 2007/01/16 21:41:13 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.100 2007/02/17 00:55:57 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2165,6 +2165,40 @@ do_numeric_accum(ArrayType *transarray, Numeric newval)
 	return result;
 }
 
+/*
+ * Improve avg performance by not caclulating sum(X*X).
+ */
+static ArrayType *
+do_numeric_avg_accum(ArrayType *transarray, Numeric newval)
+{
+	Datum	   *transdatums;
+	int			ndatums;
+	Datum		N,
+				sumX;
+	ArrayType  *result;
+
+	/* We assume the input is array of numeric */
+	deconstruct_array(transarray,
+					  NUMERICOID, -1, false, 'i',
+					  &transdatums, NULL, &ndatums);
+	if (ndatums != 2)
+		elog(ERROR, "expected 2-element numeric array");
+	N = transdatums[0];
+	sumX = transdatums[1];
+
+	N = DirectFunctionCall1(numeric_inc, N);
+	sumX = DirectFunctionCall2(numeric_add, sumX,
+							   NumericGetDatum(newval));
+
+	transdatums[0] = N;
+	transdatums[1] = sumX;
+
+	result = construct_array(transdatums, 2,
+							 NUMERICOID, -1, false, 'i');
+
+	return result;
+}
+
 Datum
 numeric_accum(PG_FUNCTION_ARGS)
 {
@@ -2174,6 +2208,18 @@ numeric_accum(PG_FUNCTION_ARGS)
 	PG_RETURN_ARRAYTYPE_P(do_numeric_accum(transarray, newval));
 }
 
+/*
+ * Optimized case for average of numeric.
+ */
+Datum
+numeric_avg_accum(PG_FUNCTION_ARGS)
+{
+	ArrayType  *transarray = PG_GETARG_ARRAYTYPE_P(0);
+	Numeric		newval = PG_GETARG_NUMERIC(1);
+
+	PG_RETURN_ARRAYTYPE_P(do_numeric_avg_accum(transarray, newval));
+}
+
 /*
  * Integer data types all use Numeric accumulators to share code and
  * avoid risk of overflow.	For int2 and int4 inputs, Numeric accumulation
@@ -2219,6 +2265,22 @@ int8_accum(PG_FUNCTION_ARGS)
 	PG_RETURN_ARRAYTYPE_P(do_numeric_accum(transarray, newval));
 }
 
+/*
+ * Optimized case for average of int8.
+ */
+Datum
+int8_avg_accum(PG_FUNCTION_ARGS)
+{
+	ArrayType  *transarray = PG_GETARG_ARRAYTYPE_P(0);
+	Datum		newval8 = PG_GETARG_DATUM(1);
+	Numeric		newval;
+
+	newval = DatumGetNumeric(DirectFunctionCall1(int8_numeric, newval8));
+
+	PG_RETURN_ARRAYTYPE_P(do_numeric_avg_accum(transarray, newval));
+}
+
+
 Datum
 numeric_avg(PG_FUNCTION_ARGS)
 {
@@ -2232,11 +2294,10 @@ numeric_avg(PG_FUNCTION_ARGS)
 	deconstruct_array(transarray,
 					  NUMERICOID, -1, false, 'i',
 					  &transdatums, NULL, &ndatums);
-	if (ndatums != 3)
+	if (ndatums != 2)
-		elog(ERROR, "expected 3-element numeric array");
+		elog(ERROR, "expected 2-element numeric array");
 	N = DatumGetNumeric(transdatums[0]);
 	sumX = DatumGetNumeric(transdatums[1]);
-	/* ignore sumX2 */
 
 	/* SQL92 defines AVG of no values to be NULL */
 	/* N is zero iff no digits (cf. numeric_uminus) */

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.385 2007/02/16 07:46:55 petere Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.386 2007/02/17 00:55:57 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200702161
+#define CATALOG_VERSION_NO	200702162
 
 #endif

src/include/catalog/pg_aggregate.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_aggregate.h,v 1.60 2007/01/20 09:27:19 petere Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_aggregate.h,v 1.61 2007/02/17 00:55:57 momjian Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -80,10 +80,10 @@ typedef FormData_pg_aggregate *Form_pg_aggregate;
  */
 
 /* avg */
-DATA(insert ( 2100	int8_accum		numeric_avg		0	1231	"{0,0,0}" ));
+DATA(insert ( 2100	int8_avg_accum	numeric_avg		0	1231	"{0,0}" ));
 DATA(insert ( 2101	int4_avg_accum	int8_avg		0	1016	"{0,0}" ));
 DATA(insert ( 2102	int2_avg_accum	int8_avg		0	1016	"{0,0}" ));
-DATA(insert ( 2103	numeric_accum	numeric_avg		0	1231	"{0,0,0}" ));
+DATA(insert ( 2103	numeric_avg_accum	numeric_avg		0	1231	"{0,0}" ));
 DATA(insert ( 2104	float4_accum	float8_avg		0	1022	"{0,0,0}" ));
 DATA(insert ( 2105	float8_accum	float8_avg		0	1022	"{0,0,0}" ));
 DATA(insert ( 2106	interval_accum	interval_avg	0	1187	"{0 second,0 second}" ));

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.444 2007/02/16 07:46:55 petere Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.445 2007/02/17 00:55:57 momjian Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -2744,12 +2744,16 @@ DATA(insert OID = 1832 (  float8_stddev_samp	PGNSP PGUID 12 1 0 f f t f i 1 701
 DESCR("STDDEV_SAMP aggregate final function");
 DATA(insert OID = 1833 (  numeric_accum    PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 1700" _null_ _null_ _null_ numeric_accum - _null_ ));
 DESCR("aggregate transition function");
+DATA(insert OID = 2858 (  numeric_avg_accum    PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 1700" _null_ _null_ _null_ numeric_avg_accum - _null_ ));
+DESCR("aggregate transition function");
 DATA(insert OID = 1834 (  int2_accum	   PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 21" _null_ _null_ _null_ int2_accum - _null_ ));
 DESCR("aggregate transition function");
 DATA(insert OID = 1835 (  int4_accum	   PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 23" _null_ _null_ _null_ int4_accum - _null_ ));
 DESCR("aggregate transition function");
 DATA(insert OID = 1836 (  int8_accum	   PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 20" _null_ _null_ _null_ int8_accum - _null_ ));
 DESCR("aggregate transition function");
+DATA(insert OID = 2746 (  int8_avg_accum	   PGNSP PGUID 12 1 0 f f t f i 2 1231 "1231 20" _null_ _null_ _null_ int8_avg_accum - _null_ ));
+DESCR("aggregate transition function");
 DATA(insert OID = 1837 (  numeric_avg	   PGNSP PGUID 12 1 0 f f t f i 1 1700 "1231" _null_ _null_ _null_	numeric_avg - _null_ ));
 DESCR("AVG aggregate final function");
 DATA(insert OID = 2514 (  numeric_var_pop  PGNSP PGUID 12 1 0 f f t f i 1 1700 "1231" _null_ _null_ _null_	numeric_var_pop - _null_ ));

src/include/utils/builtins.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.287 2007/01/28 16:16:54 neilc Exp $
+ * $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.288 2007/02/17 00:55:58 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -841,9 +841,11 @@ extern Datum numeric_float4(PG_FUNCTION_ARGS);
 extern Datum text_numeric(PG_FUNCTION_ARGS);
 extern Datum numeric_text(PG_FUNCTION_ARGS);
 extern Datum numeric_accum(PG_FUNCTION_ARGS);
+extern Datum numeric_avg_accum(PG_FUNCTION_ARGS);
 extern Datum int2_accum(PG_FUNCTION_ARGS);
 extern Datum int4_accum(PG_FUNCTION_ARGS);
 extern Datum int8_accum(PG_FUNCTION_ARGS);
+extern Datum int8_avg_accum(PG_FUNCTION_ARGS);
 extern Datum numeric_avg(PG_FUNCTION_ARGS);
 extern Datum numeric_var_pop(PG_FUNCTION_ARGS);
 extern Datum numeric_var_samp(PG_FUNCTION_ARGS);

src/test/regress/expected/create_aggregate.out

@@ -3,9 +3,9 @@
 --
 -- all functions CREATEd
 CREATE AGGREGATE newavg (
-   sfunc = int4_accum, basetype = int4, stype = _numeric, 
+   sfunc = int4_avg_accum, basetype = int4, stype = _int8, 
-   finalfunc = numeric_avg,
+   finalfunc = int8_avg,
-   initcond1 = '{0,0,0}'
+   initcond1 = '{0,0}'
 );
 -- test comments
 COMMENT ON AGGREGATE newavg_wrong (int4) IS 'an agg comment';

src/test/regress/sql/create_aggregate.sql

@@ -4,9 +4,9 @@
 
 -- all functions CREATEd
 CREATE AGGREGATE newavg (
-   sfunc = int4_accum, basetype = int4, stype = _numeric, 
+   sfunc = int4_avg_accum, basetype = int4, stype = _int8, 
-   finalfunc = numeric_avg,
+   finalfunc = int8_avg,
-   initcond1 = '{0,0,0}'
+   initcond1 = '{0,0}'
 );
 
 -- test comments