MB-32691 Detect nested correlation in FROM clause

Currently correlation is checked by references in the query block,
and marked on the SELECT. In the repro case we have nested subqueries
in the FROM clause. We correctly detected the inner most query block
as correlated, but not the intermediate subquery level since the
only correlation is in the FROM clause subquery which is currently
not detected.

Add a function to detect correlation in the FROM term interface
such that any correlated subquery or expression term in the FROM
clause can be easily determined, and set the correlation flag
in SELECT if such correlation is detected.

Change-Id: I2c9512ab7f7c79c58013af5d62162d6e1b0e192e
Reviewed-on: http://review.couchbase.org/c/query/+/142590
Reviewed-by: Sitaram Vemulapalli <sitaram.vemulapalli@couchbase.com>
Tested-by: Bingjie Miao <bingjie.miao@couchbase.com>

algebra/from.go

@@ -58,6 +58,11 @@ type FromTerm interface {
 	   Represents alias string.
 	*/
 	Alias() string
+
+	/*
+	   Contains correlation reference?
+	*/
+	IsCorrelated() bool
 }
 
 type SimpleFromTerm interface {

algebra/from_join.go

@@ -158,6 +158,13 @@ func (this *Join) Outer() bool {
 	return this.outer
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *Join) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input JOIN terms.
 */

algebra/from_join_ansi.go

@@ -235,6 +235,13 @@ func (this *AnsiJoin) SetHintError(hintError string) {
 	}
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *AnsiJoin) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input JOIN terms.
 */

algebra/from_join_index.go

@@ -171,6 +171,13 @@ func (this *IndexJoin) For() string {
 	return this.keyFor
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *IndexJoin) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input JOIN terms.
 */

algebra/from_keyspace.go

@@ -487,6 +487,13 @@ func (this *KeyspaceTerm) SetIndexJoinNest() {
 	this.property |= TERM_INDEX_JOIN_NEST
 }
 
+/*
+Return whether correlated
+*/
+func (this *KeyspaceTerm) IsCorrelated() bool {
+	return false
+}
+
 /*
 Marshals the input keyspace into a byte array.
 */

algebra/from_nest.go

@@ -162,6 +162,13 @@ func (this *Nest) Outer() bool {
 	return this.outer
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *Nest) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input NEST terms into byte array.
 */

algebra/from_nest_ansi.go

@@ -217,6 +217,13 @@ func (this *AnsiNest) SetHintError(hintError string) {
 	}
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *AnsiNest) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input NEST terms into byte array.
 */

algebra/from_nest_index.go

@@ -174,6 +174,13 @@ func (this *IndexNest) For() string {
 	return this.keyFor
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *IndexNest) IsCorrelated() bool {
+	return this.left.IsCorrelated() || this.right.IsCorrelated()
+}
+
 /*
 Marshals input NEST terms into byte array.
 */

algebra/from_subquery.go

@@ -188,3 +188,10 @@ Set ANSI NEST property
 func (this *SubqueryTerm) SetAnsiNest() {
 	this.property |= TERM_ANSI_NEST
 }
+
+/*
+Return whether correlated
+*/
+func (this *SubqueryTerm) IsCorrelated() bool {
+	return this.subquery.IsCorrelated()
+}

algebra/from_unnest.go

@@ -175,6 +175,13 @@ func (this *Unnest) Outer() bool {
 	return this.outer
 }
 
+/*
+Returns whether contains correlation reference
+*/
+func (this *Unnest) IsCorrelated() bool {
+	return this.left.IsCorrelated()
+}
+
 /*
 Marshals input unnest terms into byte array.
 */

algebra/select_sub.go

@@ -142,6 +142,10 @@ func (this *Subselect) Formalize(parent *expression.Formalizer) (f *expression.F
 		}
 	}
 
+	if !this.correlated && this.from != nil && this.from.IsCorrelated() {
+		this.correlated = true
+	}
+
 	return f, nil
 }