Feature #2058 - Window Function: frame exclude clause

Author: asfernandes

doc/sql.extensions/README.window_functions.md

@@ -4,7 +4,7 @@ By the SQL specification, window functions (also know as analytical functions) a
 
 That sort of functions are used with the `OVER` clause. Window functions may appear only in the select list or the `ORDER BY` clause of a query.
 
-Additional to the `OVER` clause, Firebird window functions may use partitions, order and frames (FB 4.0).
+Additional to the `OVER` clause, Firebird window functions may use partitions, order, frames (FB 4.0) and frame exclusions (FB 6.0).
 
 Syntax:
 
@@ -14,7 +14,7 @@ Syntax:
     OVER {<window specification> | <existing window name>}
 
 <window specification> ::=
-  ([<existing window name>] [<window partition>] [<window order>] [<window frame>])
+  ([<existing window name>] [<window partition>] [<window order>] [<window frame>] [<window frame exclusion>])
 
 <window partition> ::=
   PARTITION BY <expr> [, <expr> ...]
@@ -35,6 +35,9 @@ Syntax:
   BETWEEN {UNBOUNDED PRECEDING | <expr> PRECEDING | <expr> FOLLOWING | CURRENT ROW} AND
           {UNBOUNDED FOLLOWING | <expr> PRECEDING | <expr> FOLLOWING | CURRENT ROW}
 
+<window frame exclusion> ::=
+  EXCLUDE {NO OTHERS | CURRENT ROW | GROUP | TIES}
+
 <direction> ::=
   {ASC | DESC}
 
@@ -279,6 +282,28 @@ With `ROWS`, order expressions is not limited by number or types. In this case,
 
 The frame syntax with `<window frame start>` specifies the start frame, with the end frame being `CURRENT ROW`.
 
+The optional frame exclusion clause (FB 6.0) removes rows from the frame after its bounds have been evaluated. `EXCLUDE NO OTHERS` is the default and keeps the frame unchanged.
+
+`EXCLUDE CURRENT ROW` removes only the current row from the frame.
+
+`EXCLUDE GROUP` removes the current row and all its peers. Peers are rows with the same `ORDER BY` values as the current row. If there is no `ORDER BY`, all rows in the partition are peers.
+
+`EXCLUDE TIES` removes the peers of the current row, but keeps the current row itself. If there is no `ORDER BY`, all other rows in the partition are removed from the frame.
+
+For example, with duplicate salaries, the following query sums the full ordered partition except the current salary peer group:
+
+```sql
+select
+    id,
+    salary,
+    sum(salary) over (
+      order by salary
+      rows between unbounded preceding and unbounded following
+      exclude group
+    ) sum_other_salaries
+  from employee
+  order by salary;
+```
 
 
 When `ORDER BY` window clause is used but frame clause is omitted, it defaults to `RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW`. This fact makes the query below to produce "weird" behaviour for the "sum_salary" column. It sums from the partition start to the current key, instead of sum the whole partition.
@@ -346,9 +371,9 @@ select
 |  5 |  10.00 |           3 |
 |  2 |  12.00 |           1 |
 
-Some window functions discard frames. `ROW_NUMBER`, `LAG` and `LEAD` always work as `ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW`. And `DENSE_RANK`, `RANK`, `PERCENT_RANK` and `CUME_DIST` always work as `RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW`.
+Some window functions discard frames and frame exclusions. `ROW_NUMBER`, `LAG` and `LEAD` always work as `ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW`. And `DENSE_RANK`, `RANK`, `PERCENT_RANK` and `CUME_DIST` always work as `RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW`.
 
-`FIRST_VALUE`, `LAST_VALUE` and `NTH_VALUE` respect frames, but the `RANGE` unit works identically as `ROWS`.
+`FIRST_VALUE`, `LAST_VALUE` and `NTH_VALUE` respect frames and frame exclusions, but the `RANGE` unit works identically as `ROWS`.
 
 ## 6. Named windows (FB 4.0)
 

src/dsql/ExprNodes.cpp

@@ -9644,12 +9644,14 @@ ValueExprNode* OverNode::dsqlPass(DsqlCompilerScratch* dsqlScratch)
 	const AggNode* aggNode = nodeAs<AggNode>(node->aggExpr);
 
 	if (node->window &&
-		node->window->extent &&
 		aggNode &&
+		(node->window->extent || node->window->exclusion != WindowClause::Exclusion::NO_OTHERS) &&
 		(aggNode->getCapabilities() & AggNode::CAP_RESPECTS_WINDOW_FRAME) !=
 			AggNode::CAP_RESPECTS_WINDOW_FRAME)
 	{
-		node->window->extent = WindowClause::FrameExtent::createDefault(dsqlScratch->getPool());
+		if (node->window->extent)
+			node->window->extent = WindowClause::FrameExtent::createDefault(dsqlScratch->getPool());
+
 		node->window->exclusion = WindowClause::Exclusion::NO_OTHERS;
 	}
 

src/dsql/WinNodes.cpp

@@ -436,7 +436,7 @@ void FirstValueWinNode::aggInit(thread_db* tdbb, Request* request) const
 
 dsc* FirstValueWinNode::winPass(thread_db* tdbb, Request* request, SlidingWindow* window) const
 {
-	if (!window->moveWithinFrame(-window->getInFrameOffset()))
+	if (!window->moveToFrameStart())
 		return nullptr;
 
 	dsc* desc = EVL_expr(tdbb, request, arg);
@@ -497,7 +497,7 @@ void LastValueWinNode::aggInit(thread_db* tdbb, Request* request) const
 
 dsc* LastValueWinNode::winPass(thread_db* tdbb, Request* request, SlidingWindow* window) const
 {
-	if (!window->moveWithinFrame(window->getFrameEnd() - window->getRecordPosition()))
+	if (!window->moveToFrameEnd())
 		return nullptr;
 
 	dsc* desc = EVL_expr(tdbb, request, arg);
@@ -587,11 +587,11 @@ dsc* NthValueWinNode::winPass(thread_db* tdbb, Request* request, SlidingWindow*
 	const SLONG fromPos = desc ? MOV_get_long(tdbb, desc, 0) : FROM_FIRST;
 
 	if (fromPos == FROM_FIRST)
-		records -= window->getInFrameOffset() + 1;
+		--records;
 	else
-		records = window->getFrameEnd() - window->getRecordPosition() - records + 1;
+		records = window->getEffectiveFrameSize() - records;
 
-	if (!window->moveWithinFrame(records))
+	if (!window->moveToFrameOffset(records))
 		return nullptr;
 
 	desc = EVL_expr(tdbb, request, arg);

src/jrd/RecordSourceNodes.cpp

@@ -2656,11 +2656,6 @@ void WindowSourceNode::parseWindow(thread_db* tdbb, CompilerScratch* csb)
 				break;
 
 			case blr_window_win_exclusion:
-				//// TODO: CORE-5338 - write code for execution.
-				PAR_error(csb,
-					Arg::Gds(isc_wish_list) <<
-					Arg::Gds(isc_random) << "window EXCLUDE clause");
-
 				window.exclusion = (WindowClause::Exclusion) csb->csb_blr_reader.getByte();
 
 				switch (window.exclusion)

src/jrd/recsrc/RecordSource.h

@@ -770,41 +770,43 @@ namespace Jrd
 	{
 	public:
 		SlidingWindow(thread_db* aTdbb, const BaseBufferedStream* aStream, Request* request,
-			FB_UINT64 aPartitionStart, FB_UINT64 aPartitionEnd,
-			FB_UINT64 aFrameStart, FB_UINT64 aFrameEnd);
+			SINT64 aPartitionStart, SINT64 aPartitionEnd,
+			SINT64 aFrameStart, SINT64 aFrameEnd,
+			SINT64 aExclusionStart1, SINT64 aExclusionEnd1,
+			SINT64 aExclusionStart2, SINT64 aExclusionEnd2);
 		~SlidingWindow();
 
-		FB_UINT64 getPartitionStart() const
+		SINT64 getPartitionStart() const
 		{
 			return partitionStart;
 		}
 
-		FB_UINT64 getPartitionEnd() const
+		SINT64 getPartitionEnd() const
 		{
 			return partitionEnd;
 		}
 
-		FB_UINT64 getPartitionSize() const
+		SINT64 getPartitionSize() const
 		{
 			return partitionEnd - partitionStart + 1;
 		}
 
-		FB_UINT64 getFrameStart() const
+		SINT64 getFrameStart() const
 		{
 			return frameStart;
 		}
 
-		FB_UINT64 getFrameEnd() const
+		SINT64 getFrameEnd() const
 		{
 			return frameEnd;
 		}
 
-		FB_UINT64 getFrameSize() const
+		SINT64 getFrameSize() const
 		{
-			return frameEnd - frameStart + 1;
+			return getEffectiveFrameSize();
 		}
 
-		FB_UINT64 getRecordPosition() const
+		SINT64 getRecordPosition() const
 		{
 			return savedPosition;
 		}
@@ -825,15 +827,37 @@ namespace Jrd
 
 		bool moveWithinPartition(SINT64 delta);
 		bool moveWithinFrame(SINT64 delta);
+		bool moveToFrameStart();
+		bool moveToFrameEnd();
+		bool moveToFrameOffset(SINT64 offset);
+		SINT64 getEffectiveFrameSize() const;
+
+	private:
+		bool hasFrame() const
+		{
+			return frameStart <= frameEnd && frameStart >= partitionStart && frameEnd <= partitionEnd;
+		}
+
+		bool isExcluded(SINT64 position) const
+		{
+			return (position >= exclusionStart1 && position <= exclusionEnd1) ||
+				(position >= exclusionStart2 && position <= exclusionEnd2);
+		}
+
+		bool moveToFramePosition(SINT64 position);
 
 	private:
 		thread_db* tdbb;
 		const BaseBufferedStream* const stream;
-		FB_UINT64 partitionStart;
-		FB_UINT64 partitionEnd;
-		FB_UINT64 frameStart;
-		FB_UINT64 frameEnd;
-		FB_UINT64 savedPosition;
+		SINT64 partitionStart;
+		SINT64 partitionEnd;
+		SINT64 frameStart;
+		SINT64 frameEnd;
+		SINT64 exclusionStart1;
+		SINT64 exclusionEnd1;
+		SINT64 exclusionStart2;
+		SINT64 exclusionEnd2;
+		SINT64 savedPosition;
 		bool moved = false;
 	};
 
@@ -1032,6 +1056,12 @@ namespace Jrd
 			void getFrameValue(thread_db* tdbb, Request* request,
 				const Frame* frame, impure_value_ex* impureValue) const;
 
+			Block getPeerBlock(thread_db* tdbb, Request* request, Impure* impure,
+				SINT64 position) const;
+			void getExclusionBlocks(thread_db* tdbb, Request* request, Impure* impure,
+				SINT64 position, Block* exclusion1, Block* exclusion2) const;
+			bool isExcluded(SINT64 position, const Block& exclusion1, const Block& exclusion2) const;
+
 			SINT64 locateFrameRange(thread_db* tdbb, Request* request, Impure* impure,
 				const Frame* frame, const dsc* offsetDesc, SINT64 position) const;