fix(spanddl): support dropping interleaved tables

Before the parent would have an reference to the dropped table, which
caused an type error since the type could not be resolved.

This PR removes the child reference in the parent table.

spanddl/database.go

@@ -127,6 +127,7 @@ func (d *Database) applyDropTable(stmt *spansql.DropTable) (err error) {
 		return fmt.Errorf("table %s has interleaved tables %s", stmt.Name, strings.Join(names, ", "))
 	}
 	d.Tables = append(d.Tables[:i], d.Tables[i+1:]...)
+	d.removeInterleavedReferenceFromParentTable(stmt.Name)
 	return nil
 }
 
@@ -185,3 +186,20 @@ func (d *Database) indexOfIndex(name spansql.ID) int {
 	}
 	return -1
 }
+
+func (d *Database) removeInterleavedReferenceFromParentTable(name spansql.ID) {
+	for _, table := range d.Tables {
+		index := -1
+		for i, it := range table.InterleavedTables {
+			if it.Name == name {
+				index = i
+				break
+			}
+		}
+		if index >= 0 {
+			// Parent table found
+			table.InterleavedTables = append(table.InterleavedTables[:index], table.InterleavedTables[index+1:]...)
+			return
+		}
+	}
+}

spanddl/database_test.go

@@ -292,6 +292,46 @@ func TestDatabase_ApplyDDL(t *testing.T) {
 			},
 		},
 
+		{
+			name: "drop interleaved",
+			ddls: []string{
+				`CREATE TABLE Singers (
+				  SingerId   INT64 NOT NULL,
+				  FirstName  STRING(1024),
+				  LastName   STRING(1024),
+				  SingerInfo BYTES(MAX),
+				  BirthDate  DATE,
+				) PRIMARY KEY(SingerId);`,
+
+				`CREATE TABLE Albums (
+				  SingerId     INT64 NOT NULL,
+				  AlbumId      INT64 NOT NULL,
+				  AlbumTitle   STRING(MAX),
+				) PRIMARY KEY (SingerId, AlbumId),
+				  INTERLEAVE IN PARENT Singers ON DELETE CASCADE;`,
+
+				`DROP TABLE Albums;`,
+			},
+			expected: &Database{
+				Tables: []*Table{
+					{
+						Name: "Singers",
+						Columns: []*Column{
+							{Name: "SingerId", Type: spansql.Type{Base: spansql.Int64}, NotNull: true},
+							{Name: "FirstName", Type: spansql.Type{Base: spansql.String, Len: 1024}},
+							{Name: "LastName", Type: spansql.Type{Base: spansql.String, Len: 1024}},
+							{Name: "SingerInfo", Type: spansql.Type{Base: spansql.Bytes, Len: spansql.MaxLen}},
+							{Name: "BirthDate", Type: spansql.Type{Base: spansql.Date}},
+						},
+						PrimaryKey: []spansql.KeyPart{
+							{Column: "SingerId"},
+						},
+						InterleavedTables: []*Table{},
+					},
+				},
+			},
+		},
+
 		{
 			name: "drop table with interleaved tables",
 			ddls: []string{

testdata/migrations/music/000002_create_drop_genres.up.sql

@@ -0,0 +1,8 @@
+-- This migration should result in no schema changes.
+CREATE TABLE Genres (
+                        SingerId     INT64 NOT NULL,
+                        GenreId      INT64 NOT NULL,
+) PRIMARY KEY (SingerId, GenreId),
+  INTERLEAVE IN PARENT Singers ON DELETE CASCADE;
+
+DROP TABLE Genres;