rm union flag

Author: elianddb

sql/analyzer/costed_index_scan.go

@@ -114,8 +114,8 @@ func indexSearchableLookup(ctx *sql.Context, n sql.Node, rt sql.TableNode, looku
 		ret = plan.NewFilter(newFilter, ret)
 	}
 
-	if fds != nil && fds.HasMax1Row() && !qFlags.JoinIsSet() && !qFlags.SubqueryIsSet() && !qFlags.IsSet(sql.QFlagUnion) && lookup.Ranges.Len() == 1 {
-		// Index lookup without join/subquery/union scope returns
+	if fds != nil && fds.HasMax1Row() && !qFlags.JoinIsSet() && !qFlags.SubqueryIsSet() && lookup.Ranges.Len() == 1 {
+		// Strict index lookup without a join or subquery scope will return
 		// at most one row. We could also use some sort of scope counting
 		// to check for single scope.
 		qFlags.Set(sql.QFlagMax1Row)

sql/analyzer/resolve_unions.go

@@ -41,9 +41,6 @@ func resolveUnions(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope,
 		subqueryCtx, cancelFunc := ctx.NewSubContext()
 		defer cancelFunc()
 
-		// Prevent max1Row optimization in union branches
-		qFlags.Set(sql.QFlagUnion)
-
 		left, _, err := a.analyzeThroughBatch(subqueryCtx, u.Left(), scope, "default-rules", sel, qFlags)
 		if err != nil {
 			return nil, transform.SameTree, err
@@ -82,9 +79,6 @@ func finalizeUnions(ctx *sql.Context, a *Analyzer, n sql.Node, scope *plan.Scope
 		subqueryCtx, cancelFunc := ctx.NewSubContext()
 		defer cancelFunc()
 
-		// Prevent max1Row optimization in union branches
-		qFlags.Set(sql.QFlagUnion)
-
 		scope.SetJoin(false)
 		// TODO we could detect tree modifications here, skip rebuilding
 		left, _, err := a.analyzeStartingAtBatch(subqueryCtx, u.Left(), scope, "default-rules", NewFinalizeUnionSel(sel), qFlags)

sql/query_flags.go

@@ -41,7 +41,6 @@ const (
 	QFlagLimit
 	QFlagInterval
 	QFlagAnyAgg
-	QFlagUnion
 
 	// QFlagMax1Row indicates that a query can only return at most one row
 	QFlagMax1Row