Add min and max aggregates for composite types (records).

Like min/max for arrays, these are just thin wrappers around
the existing btree comparison function for records.

Aleksander Alekseev

Discussion: https://postgr.es/m/CAO=iB8L4WYSNxCJ8GURRjQsrXEQ2-zn3FiCsh2LMqvWq2WcONg@mail.gmail.com

doc/src/sgml/func.sgml

@@ -22048,7 +22048,7 @@ SELECT NULLIF(value, '(none)') ...
         as well as <type>inet</type>, <type>interval</type>,
         <type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
         <type>tid</type>, <type>xid8</type>,
-        and arrays of any of these types.
+        and also arrays and composite types containing sortable data types.
        </para></entry>
        <entry>Yes</entry>
       </row>
@@ -22067,7 +22067,7 @@ SELECT NULLIF(value, '(none)') ...
         as well as <type>inet</type>, <type>interval</type>,
         <type>money</type>, <type>oid</type>, <type>pg_lsn</type>,
         <type>tid</type>, <type>xid8</type>,
-        and arrays of any of these types.
+        and also arrays and composite types containing sortable data types.
        </para></entry>
        <entry>Yes</entry>
       </row>

src/backend/utils/adt/rowtypes.c

@@ -1315,6 +1315,24 @@ btrecordcmp(PG_FUNCTION_ARGS)
 	PG_RETURN_INT32(record_cmp(fcinfo));
 }
 
+Datum
+record_larger(PG_FUNCTION_ARGS)
+{
+	if (record_cmp(fcinfo) > 0)
+		PG_RETURN_DATUM(PG_GETARG_DATUM(0));
+	else
+		PG_RETURN_DATUM(PG_GETARG_DATUM(1));
+}
+
+Datum
+record_smaller(PG_FUNCTION_ARGS)
+{
+	if (record_cmp(fcinfo) < 0)
+		PG_RETURN_DATUM(PG_GETARG_DATUM(0));
+	else
+		PG_RETURN_DATUM(PG_GETARG_DATUM(1));
+}
+
 
 /*
  * record_image_cmp :

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202407101
+#define CATALOG_VERSION_NO	202407111
 
 #endif

src/include/catalog/pg_aggregate.dat

@@ -140,6 +140,9 @@
 { aggfnoid => 'max(anyarray)', aggtransfn => 'array_larger',
   aggcombinefn => 'array_larger', aggsortop => '>(anyarray,anyarray)',
   aggtranstype => 'anyarray' },
+{ aggfnoid => 'max(record)', aggtransfn => 'record_larger',
+  aggcombinefn => 'record_larger', aggsortop => '>(record,record)',
+  aggtranstype => 'record' },
 { aggfnoid => 'max(bpchar)', aggtransfn => 'bpchar_larger',
   aggcombinefn => 'bpchar_larger', aggsortop => '>(bpchar,bpchar)',
   aggtranstype => 'bpchar' },
@@ -208,6 +211,9 @@
 { aggfnoid => 'min(anyarray)', aggtransfn => 'array_smaller',
   aggcombinefn => 'array_smaller', aggsortop => '<(anyarray,anyarray)',
   aggtranstype => 'anyarray' },
+{ aggfnoid => 'min(record)', aggtransfn => 'record_smaller',
+  aggcombinefn => 'record_smaller', aggsortop => '<(record,record)',
+  aggtranstype => 'record' },
 { aggfnoid => 'min(bpchar)', aggtransfn => 'bpchar_smaller',
   aggcombinefn => 'bpchar_smaller', aggsortop => '<(bpchar,bpchar)',
   aggtranstype => 'bpchar' },

src/include/catalog/pg_proc.dat

@@ -6754,6 +6754,9 @@
   proname => 'max', prokind => 'a', proisstrict => 'f',
   prorettype => 'anyarray', proargtypes => 'anyarray',
   prosrc => 'aggregate_dummy' },
+{ oid => '8595', descr => 'maximum value of all record input values',
+  proname => 'max', prokind => 'a', proisstrict => 'f', prorettype => 'record',
+  proargtypes => 'record', prosrc => 'aggregate_dummy' },
 { oid => '2244', descr => 'maximum value of all bpchar input values',
   proname => 'max', prokind => 'a', proisstrict => 'f', prorettype => 'bpchar',
   proargtypes => 'bpchar', prosrc => 'aggregate_dummy' },
@@ -6824,6 +6827,9 @@
   proname => 'min', prokind => 'a', proisstrict => 'f',
   prorettype => 'anyarray', proargtypes => 'anyarray',
   prosrc => 'aggregate_dummy' },
+{ oid => '8596', descr => 'minimum value of all record input values',
+  proname => 'min', prokind => 'a', proisstrict => 'f', prorettype => 'record',
+  proargtypes => 'record', prosrc => 'aggregate_dummy' },
 { oid => '2245', descr => 'minimum value of all bpchar input values',
   proname => 'min', prokind => 'a', proisstrict => 'f', prorettype => 'bpchar',
   proargtypes => 'bpchar', prosrc => 'aggregate_dummy' },
@@ -8343,7 +8349,7 @@
   prosrc => 'generate_series_timestamptz' },
 { oid => '6274', descr => 'non-persistent series generator',
   proname => 'generate_series', prorows => '1000',
-  prosupport => 'generate_series_timestamp_support',  proretset => 't',
+  prosupport => 'generate_series_timestamp_support', proretset => 't',
   prorettype => 'timestamptz',
   proargtypes => 'timestamptz timestamptz interval text',
   prosrc => 'generate_series_timestamptz_at_zone' },
@@ -10358,6 +10364,12 @@
 { oid => '2987', descr => 'less-equal-greater',
   proname => 'btrecordcmp', prorettype => 'int4',
   proargtypes => 'record record', prosrc => 'btrecordcmp' },
+{ oid => '8597', descr => 'larger of two',
+  proname => 'record_larger', prorettype => 'record',
+  proargtypes => 'record record', prosrc => 'record_larger' },
+{ oid => '8598', descr => 'smaller of two',
+  proname => 'record_smaller', prorettype => 'record',
+  proargtypes => 'record record', prosrc => 'record_smaller' },
 
 { oid => '6192', descr => 'hash',
   proname => 'hash_record', prorettype => 'int4', proargtypes => 'record',

src/test/regress/expected/aggregates.out

@@ -269,6 +269,31 @@ SELECT stddev_pop('nan'::numeric), stddev_samp('nan'::numeric);
         NaN |            
 (1 row)
 
+-- verify correct results for min(record) and max(record) aggregates
+SELECT max(row(a,b)) FROM aggtest;
+     max      
+--------------
+ (100,99.097)
+(1 row)
+
+SELECT max(row(b,a)) FROM aggtest;
+     max     
+-------------
+ (324.78,42)
+(1 row)
+
+SELECT min(row(a,b)) FROM aggtest;
+     min     
+-------------
+ (0,0.09561)
+(1 row)
+
+SELECT min(row(b,a)) FROM aggtest;
+     min     
+-------------
+ (0.09561,0)
+(1 row)
+
 -- verify correct results for null and NaN inputs
 select sum(null::int4) from generate_series(1,3);
  sum 

src/test/regress/sql/aggregates.sql

@@ -78,6 +78,12 @@ SELECT stddev_pop('inf'::numeric), stddev_samp('inf'::numeric);
 SELECT var_pop('nan'::numeric), var_samp('nan'::numeric);
 SELECT stddev_pop('nan'::numeric), stddev_samp('nan'::numeric);
 
+-- verify correct results for min(record) and max(record) aggregates
+SELECT max(row(a,b)) FROM aggtest;
+SELECT max(row(b,a)) FROM aggtest;
+SELECT min(row(a,b)) FROM aggtest;
+SELECT min(row(b,a)) FROM aggtest;
+
 -- verify correct results for null and NaN inputs
 select sum(null::int4) from generate_series(1,3);
 select sum(null::int8) from generate_series(1,3);