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, 28 insertions, 4 deletions

diff --git a/src/backend/access/nbtree/nbtvalidate.c b/src/backend/access/nbtree/nbtvalidate.c
index 8f4ccc87c0c..f24091c0ada 100644
--- a/src/backend/access/nbtree/nbtvalidate.c
+++ b/src/backend/access/nbtree/nbtvalidate.c
@@ -51,6 +51,7 @@ btvalidate(Oid opclassoid)
 	List	   *grouplist;
 	OpFamilyOpFuncGroup *opclassgroup;
 	List	   *familytypes;
+	int			usefulgroups;
 	int			i;
 	ListCell   *lc;
 
@@ -95,6 +96,14 @@ btvalidate(Oid opclassoid)
 				ok = check_amproc_signature(procform->amproc, VOIDOID, true,
 											1, 1, INTERNALOID);
 				break;
+			case BTINRANGE_PROC:
+				ok = check_amproc_signature(procform->amproc, BOOLOID, true,
+											5, 5,
+											procform->amproclefttype,
+											procform->amproclefttype,
+											procform->amprocrighttype,
+											BOOLOID, BOOLOID);
+				break;
 			default:
 				ereport(INFO,
 						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
@@ -165,12 +174,28 @@ btvalidate(Oid opclassoid)
 
 	/* Now check for inconsistent groups of operators/functions */
 	grouplist = identify_opfamily_groups(oprlist, proclist);
+	usefulgroups = 0;
 	opclassgroup = NULL;
 	familytypes = NIL;
 	foreach(lc, grouplist)
 	{
 		OpFamilyOpFuncGroup *thisgroup = (OpFamilyOpFuncGroup *) lfirst(lc);
 
+		/*
+		 * It is possible for an in_range support function to have a RHS type
+		 * that is otherwise irrelevant to the opfamily --- for instance, SQL
+		 * requires the datetime_ops opclass to have range support with an
+		 * interval offset.  So, if this group appears to contain only an
+		 * in_range function, ignore it: it doesn't represent a pair of
+		 * supported types.
+		 */
+		if (thisgroup->operatorset == 0 &&
+			thisgroup->functionset == (1 << BTINRANGE_PROC))
+			continue;
+
+		/* Else count it as a relevant group */
+		usefulgroups++;
+
 		/* Remember the group exactly matching the test opclass */
 		if (thisgroup->lefttype == opcintype &&
 			thisgroup->righttype == opcintype)
@@ -186,8 +211,8 @@ btvalidate(Oid opclassoid)
 
 		/*
 		 * Complain if there seems to be an incomplete set of either operators
-		 * or support functions for this datatype pair.  The only thing that
-		 * is considered optional is the sortsupport function.
+		 * or support functions for this datatype pair.  The only things
+		 * considered optional are the sortsupport and in_range functions.
 		 */
 		if (thisgroup->operatorset !=
 			((1 << BTLessStrategyNumber) |
@@ -234,8 +259,7 @@ btvalidate(Oid opclassoid)
 	 * additional qual clauses from equivalence classes, so it seems
 	 * reasonable to insist that all built-in btree opfamilies be complete.
 	 */
-	if (list_length(grouplist) !=
-		list_length(familytypes) * list_length(familytypes))
+	if (usefulgroups != (list_length(familytypes) * list_length(familytypes)))
 	{
 		ereport(INFO,
 				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),