MB-51817 Add index condition

Previous implementation only included index keys if an index
key is needed for filter evaluation. For consistency and
other potential uses, also include index conditions. Similar
to using "_index_key(expr)" instead of "cover(expr)" for
index key expressions, use "_index_condition(expr)" instead
of "cover(expr)" for index condition expressions.

Change-Id: Id0d5d9699828332c0259d71169b8c65903a95ee8
Reviewed-on: https://review.couchbase.org/c/query/+/174772
Reviewed-by: Sitaram Vemulapalli <sitaram.vemulapalli@couchbase.com>
Reviewed-by: Marco Greco <marco.greco@couchbase.com>
Tested-by: Bingjie Miao <bingjie.miao@couchbase.com>

execution/scan_index3.go

@@ -146,7 +146,7 @@ func (this *IndexScan3) RunOnce(context *Context, parent value.Value) {
 						av := this.newEmptyDocumentWithKey(entry.PrimaryKey, scope_value, context)
 						if lcovers > 0 {
 
-							for c, v := range this.plan.FilterCovers() {
+							for c, v := range this.plan.AllFilterCovers() {
 								av.SetCover(c.Text(), v)
 							}
 

expression/index_cover.go

@@ -15,14 +15,21 @@ import (
 
 type Covers []*Cover
 
+const (
+	_COVER_NONE = int32(iota)
+	_COVER_FULL
+	_COVER_KEY
+	_COVER_COND
+)
+
 /*
 Internal Expression to support covering indexing.
 */
 type Cover struct {
 	ExpressionBase
 	covered   Expression
 	text      string
-	fullCover bool
+	coverType int32
 }
 
 func NewCover(covered Expression) *Cover {
@@ -34,7 +41,7 @@ func NewCover(covered Expression) *Cover {
 	rv := &Cover{
 		covered:   covered,
 		text:      covered.String(),
-		fullCover: true,
+		coverType: _COVER_FULL,
 	}
 
 	rv.expr = rv
@@ -50,7 +57,23 @@ func NewIndexKey(covered Expression) *Cover {
 	rv := &Cover{
 		covered:   covered,
 		text:      covered.String(),
-		fullCover: false,
+		coverType: _COVER_KEY,
+	}
+
+	rv.expr = rv
+	return rv
+}
+
+func NewIndexCondition(covered Expression) *Cover {
+	switch covered := covered.(type) {
+	case *Cover:
+		return covered
+	}
+
+	rv := &Cover{
+		covered:   covered,
+		text:      covered.String(),
+		coverType: _COVER_COND,
 	}
 
 	rv.expr = rv
@@ -115,7 +138,7 @@ func (this *Cover) EquivalentTo(other Expression) bool {
 	}
 
 	oc, ok := other.(*Cover)
-	return ok && this.covered.EquivalentTo(oc.covered)
+	return ok && this.covered.EquivalentTo(oc.covered) && this.coverType == oc.coverType
 }
 
 func (this *Cover) DependsOn(other Expression) bool {
@@ -142,10 +165,12 @@ func (this *Cover) MapChildren(mapper Mapper) error {
 
 func (this *Cover) Copy() Expression {
 	var rv *Cover
-	if this.fullCover {
+	if this.coverType == _COVER_FULL {
 		rv = NewCover(this.covered.Copy())
-	} else {
+	} else if this.coverType == _COVER_KEY {
 		rv = NewIndexKey(this.covered.Copy())
+	} else if this.coverType == _COVER_COND {
+		rv = NewIndexCondition(this.covered.Copy())
 	}
 	rv.BaseCopy(this)
 	return rv
@@ -160,5 +185,13 @@ func (this *Cover) Text() string {
 }
 
 func (this *Cover) FullCover() bool {
-	return this.fullCover
+	return this.coverType == _COVER_FULL
+}
+
+func (this *Cover) IsIndexKey() bool {
+	return this.coverType == _COVER_KEY
+}
+
+func (this *Cover) IsIndexCond() bool {
+	return this.coverType == _COVER_COND
 }

expression/stringer.go

@@ -687,8 +687,12 @@ func (this *Stringer) VisitCover(expr *Cover) (interface{}, error) {
 	var buf bytes.Buffer
 	if expr.FullCover() {
 		buf.WriteString("cover (")
-	} else {
+	} else if expr.IsIndexKey() {
 		buf.WriteString("_index_key (")
+	} else if expr.IsIndexCond() {
+		buf.WriteString("_index_condition (")
+	} else {
+		return nil, fmt.Errorf("VisitCover: unexpected cover type")
 	}
 	buf.WriteString(expr.Text())
 	buf.WriteString(")")

parser/n1ql/n1ql.nex

@@ -125,6 +125,7 @@
 /;/     { yylex.logToken(yylex.Text(), "SEMI"); return SEMI }
 /\!/    { yylex.logToken(yylex.Text(), "NOT_A_TOKEN"); return NOT_A_TOKEN }
 
+/[_][iI][nN][dD][eE][xX][_][cC][oO][nN][dD][iI][tT][iI][oO][nN]/ { yylex.logToken(yylex.Text(), "_INDEX_CONDITION"); return _INDEX_CONDITION }
 /[_][iI][nN][dD][eE][xX][_][kK][eE][yY]/ { yylex.logToken(yylex.Text(), "_INDEX_KEY"); return _INDEX_KEY }
 /[aA][dD][vV][iI][sS][eE]/ {
     yylex.logToken(yylex.Text(), "ADVISE")