Support all SQL:2011 options for window frame clauses.

This patch adds the ability to use "RANGE offset PRECEDING/FOLLOWING"
frame boundaries in window functions.  We'd punted on that back in the
original patch to add window functions, because it was not clear how to
do it in a reasonably data-type-extensible fashion.  That problem is
resolved here by adding the ability for btree operator classes to provide
an "in_range" support function that defines how to add or subtract the
RANGE offset value.  Factoring it this way also allows the operator class
to avoid overflow problems near the ends of the datatype's range, if it
wishes to expend effort on that.  (In the committed patch, the integer
opclasses handle that issue, but it did not seem worth the trouble to
avoid overflow failures for datetime types.)

The patch includes in_range support for the integer_ops opfamily
(int2/int4/int8) as well as the standard datetime types.  Support for
other numeric types has been requested, but that seems like suitable
material for a follow-on patch.

In addition, the patch adds GROUPS mode which counts the offset in
ORDER-BY peer groups rather than rows, and it adds the frame_exclusion
options specified by SQL:2011.  As far as I can see, we are now fully
up to spec on window framing options.

Existing behaviors remain unchanged, except that I changed the errcode
for a couple of existing error reports to meet the SQL spec's expectation
that negative "offset" values should be reported as SQLSTATE 22013.

Internally and in relevant parts of the documentation, we now consistently
use the terminology "offset PRECEDING/FOLLOWING" rather than "value
PRECEDING/FOLLOWING", since the term "value" is confusingly vague.

Oliver Ford, reviewed and whacked around some by me

Discussion: https://postgr.es/m/CAGMVOdu9sivPAxbNN0X+q19Sfv9edEPv=HibOJhB14TJv_RCQg@mail.gmail.com

1 files changed, 25 insertions, 4 deletions

diff --git a/src/backend/commands/opclasscmds.c b/src/backend/commands/opclasscmds.c
index 1768140a830..e4b1369f193 100644
--- a/src/backend/commands/opclasscmds.c
+++ b/src/backend/commands/opclasscmds.c
@@ -1128,10 +1128,11 @@ assignProcTypes(OpFamilyMember *member, Oid amoid, Oid typeoid)
 	procform = (Form_pg_proc) GETSTRUCT(proctup);
 
 	/*
-	 * btree comparison procs must be 2-arg procs returning int4, while btree
-	 * sortsupport procs must take internal and return void.  hash support
-	 * proc 1 must be a 1-arg proc returning int4, while proc 2 must be a
-	 * 2-arg proc returning int8.  Otherwise we don't know.
+	 * btree comparison procs must be 2-arg procs returning int4.  btree
+	 * sortsupport procs must take internal and return void.  btree in_range
+	 * procs must be 5-arg procs returning bool.  hash support proc 1 must be
+	 * a 1-arg proc returning int4, while proc 2 must be a 2-arg proc
+	 * returning int8.  Otherwise we don't know.
 	 */
 	if (amoid == BTREE_AM_OID)
 	{
@@ -1171,6 +1172,26 @@ assignProcTypes(OpFamilyMember *member, Oid amoid, Oid typeoid)
 			 * Can't infer lefttype/righttype from proc, so use default rule
 			 */
 		}
+		else if (member->number == BTINRANGE_PROC)
+		{
+			if (procform->pronargs != 5)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+						 errmsg("btree in_range procedures must have five arguments")));
+			if (procform->prorettype != BOOLOID)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+						 errmsg("btree in_range procedures must return boolean")));
+
+			/*
+			 * If lefttype/righttype isn't specified, use the proc's input
+			 * types (we look at the test-value and offset arguments)
+			 */
+			if (!OidIsValid(member->lefttype))
+				member->lefttype = procform->proargtypes.values[0];
+			if (!OidIsValid(member->righttype))
+				member->righttype = procform->proargtypes.values[2];
+		}
 	}
 	else if (amoid == HASH_AM_OID)
 	{