sql: add support for optional frame exclusion

Adds support for optional frame exclusion clause in the specification
of window frames.

Release note (sql change): CockroachDB now supports optinal frame
exclusion clause in the specification of window frames.

Release note: None

docs/generated/sql/bnf/stmt_block.bnf

@@ -620,6 +620,7 @@ unreserved_keyword ::=
 	| 'ENCODING'
 	| 'ENUM'
 	| 'ESCAPE'
+	| 'EXCLUDE'
 	| 'EXECUTE'
 	| 'EXPERIMENTAL'
 	| 'EXPERIMENTAL_AUDIT'
@@ -703,6 +704,7 @@ unreserved_keyword ::=
 	| 'OPTION'
 	| 'OPTIONS'
 	| 'ORDINALITY'
+	| 'OTHERS'
 	| 'OVER'
 	| 'OWNED'
 	| 'PARENT'
@@ -789,6 +791,7 @@ unreserved_keyword ::=
 	| 'TEMPORARY'
 	| 'TESTING_RELOCATE'
 	| 'TEXT'
+	| 'TIES'
 	| 'TRACE'
 	| 'TRANSACTION'
 	| 'TRIGGER'
@@ -2287,9 +2290,9 @@ opt_partition_clause ::=
 	| 
 
 opt_frame_clause ::=
-	'RANGE' frame_extent
-	| 'ROWS' frame_extent
-	| 'GROUPS' frame_extent
+	'RANGE' frame_extent opt_frame_exclusion
+	| 'ROWS' frame_extent opt_frame_exclusion
+	| 'GROUPS' frame_extent opt_frame_exclusion
 	| 
 
 extract_list ::=
@@ -2331,6 +2334,13 @@ frame_extent ::=
 	frame_bound
 	| 'BETWEEN' frame_bound 'AND' frame_bound
 
+opt_frame_exclusion ::=
+	'EXCLUDE' 'CURRENT' 'ROW'
+	| 'EXCLUDE' 'GROUP'
+	| 'EXCLUDE' 'TIES'
+	| 'EXCLUDE' 'NO' 'OTHERS'
+	| 
+
 extract_arg ::=
 	'identifier'
 	| 'YEAR'

pkg/sql/distsqlpb/processors.go

@@ -75,6 +75,21 @@ func (spec *WindowerSpec_Frame_BoundType) initFromAST(bt tree.WindowFrameBoundTy
 	}
 }
 
+func (spec *WindowerSpec_Frame_Exclusion) initFromAST(e tree.WindowFrameExclusion) {
+	switch e {
+	case tree.NoExclusion:
+		*spec = WindowerSpec_Frame_NO_EXCLUSION
+	case tree.ExcludeCurrentRow:
+		*spec = WindowerSpec_Frame_EXCLUDE_CURRENT_ROW
+	case tree.ExcludeGroup:
+		*spec = WindowerSpec_Frame_EXCLUDE_GROUP
+	case tree.ExcludeTies:
+		*spec = WindowerSpec_Frame_EXCLUDE_TIES
+	default:
+		panic("unexpected WindowerFrameExclusion")
+	}
+}
+
 // If offset exprs are present, we evaluate them and save the encoded results
 // in the spec.
 func (spec *WindowerSpec_Frame_Bounds) initFromAST(
@@ -190,6 +205,7 @@ func isNegative(evalCtx *tree.EvalContext, offset tree.Datum) bool {
 // offset expressions if present in the frame.
 func (spec *WindowerSpec_Frame) InitFromAST(f *tree.WindowFrame, evalCtx *tree.EvalContext) error {
 	spec.Mode.initFromAST(f.Mode)
+	spec.Exclusion.initFromAST(f.Exclusion)
 	return spec.Bounds.initFromAST(f.Bounds, f.Mode, evalCtx)
 }
 
@@ -223,6 +239,21 @@ func (spec WindowerSpec_Frame_BoundType) convertToAST() tree.WindowFrameBoundTyp
 	}
 }
 
+func (spec WindowerSpec_Frame_Exclusion) convertToAST() tree.WindowFrameExclusion {
+	switch spec {
+	case WindowerSpec_Frame_NO_EXCLUSION:
+		return tree.NoExclusion
+	case WindowerSpec_Frame_EXCLUDE_CURRENT_ROW:
+		return tree.ExcludeCurrentRow
+	case WindowerSpec_Frame_EXCLUDE_GROUP:
+		return tree.ExcludeGroup
+	case WindowerSpec_Frame_EXCLUDE_TIES:
+		return tree.ExcludeTies
+	default:
+		panic("unexpected WindowerSpec_Frame_Exclusion")
+	}
+}
+
 // convertToAST produces tree.WindowFrameBounds based on
 // WindowerSpec_Frame_Bounds. Note that it might not be fully equivalent to
 // original - if offsetExprs were present in original tree.WindowFrameBounds,
@@ -239,5 +270,9 @@ func (spec WindowerSpec_Frame_Bounds) convertToAST() tree.WindowFrameBounds {
 
 // ConvertToAST produces a tree.WindowFrame given a WindoweSpec_Frame.
 func (spec *WindowerSpec_Frame) ConvertToAST() *tree.WindowFrame {
-	return &tree.WindowFrame{Mode: spec.Mode.convertToAST(), Bounds: spec.Bounds.convertToAST()}
+	return &tree.WindowFrame{
+		Mode:      spec.Mode.convertToAST(),
+		Bounds:    spec.Bounds.convertToAST(),
+		Exclusion: spec.Exclusion.convertToAST(),
+	}
 }