Better support for merging UNION routes that use IN conditions.

Signed-off-by: Arthur Schreiber <[email protected]>

Author: arthurschreiber

go/vt/vtgate/planbuilder/operators/route_planning.go

@@ -486,6 +486,13 @@ func gen4ValuesEqual(ctx *plancontext.PlanningContext, a, b []sqlparser.Expr) (b
 
 func gen4ValEqual(ctx *plancontext.PlanningContext, a, b sqlparser.Expr) (bool, *engine.Condition) {
 	switch a := a.(type) {
+	case sqlparser.ValTuple:
+		if b, ok := b.(sqlparser.ValTuple); ok {
+			return gen4ValuesEqual(ctx, a, b)
+		}
+
+		return false
+
 	case *sqlparser.ColName:
 		if b, ok := b.(*sqlparser.ColName); ok {
 			if !a.Name.Equal(b.Name) {

go/vt/vtgate/planbuilder/operators/union_merging.go

@@ -146,8 +146,6 @@ func tryMergeUnionShardedRouting(
 
 	scatterA := tblA.RouteOpCode == engine.Scatter
 	scatterB := tblB.RouteOpCode == engine.Scatter
-	uniqueA := tblA.RouteOpCode == engine.EqualUnique
-	uniqueB := tblB.RouteOpCode == engine.EqualUnique
 
 	switch {
 	case scatterA:
@@ -156,7 +154,11 @@ func tryMergeUnionShardedRouting(
 	case scatterB:
 		return createMergedUnion(ctx, routeA, routeB, exprsA, exprsB, distinct, tblB, nil)
 
-	case uniqueA && uniqueB:
+	case tblA.RouteOpCode == engine.EqualUnique && tblB.RouteOpCode == engine.EqualUnique:
+		fallthrough
+	case tblA.RouteOpCode == engine.Equal && tblB.RouteOpCode == engine.Equal:
+		fallthrough
+	case tblA.RouteOpCode == engine.IN && tblB.RouteOpCode == engine.IN:
 		aVdx := tblA.SelectedVindex()
 		bVdx := tblB.SelectedVindex()
 		aExpr := tblA.VindexExpressions()