working drop schema

Author: zachmu

core/rootvalue.go

@@ -96,9 +96,11 @@ func (root *RootValue) DropDatabaseSchema(ctx context.Context, dbSchema schema.D
 	}
 
 	found := false
+	schemaName := dbSchema.Name
 	for i, s := range schemas {
 		if strings.EqualFold(s.Name, dbSchema.Name) {
 			found = true
+			schemaName = s.Name
 			// remove this element in the slice
 			schemas = append(schemas[:i], schemas[i+1:]...)
 			break
@@ -109,6 +111,31 @@ func (root *RootValue) DropDatabaseSchema(ctx context.Context, dbSchema schema.D
 		return nil, fmt.Errorf("No schema with the name %s exists", dbSchema.Name)
 	}
 
+	// Check for dangling objects in the schema and reject the drop if there are any
+	danglingObjects := false
+	root.IterRootObjects(ctx, func(name doltdb.TableName, table doltdb.RootObject) (stop bool, err error) {
+		if strings.EqualFold(name.Schema, dbSchema.Name) {
+			danglingObjects = true
+		}
+		return false, nil
+	})
+
+	// check the tables specifically in addition to root objects. This is just an extra paranoid step to avoid
+	// removing a schema that still has tables.
+	tableMap, err := root.getTableMap(ctx, schemaName)
+	if err != nil {
+		return nil, err
+	}
+
+	tableMap.Iter(ctx, func(name string, addr hash.Hash) (bool, error) {
+		danglingObjects = true
+		return true, nil
+	})
+
+	if danglingObjects {
+		return nil, fmt.Errorf("cannot drop schema %s because other objects depend on it", dbSchema.Name)
+	}
+
 	r, err := root.st.SetSchemas(ctx, schemas)
 	if err != nil {
 		return nil, err
@@ -609,10 +636,10 @@ func (root *RootValue) PutTable(ctx context.Context, tName doltdb.TableName, tab
 
 // RemoveTables implements the interface doltdb.RootValue.
 func (root *RootValue) RemoveTables(
-		ctx context.Context,
-		skipFKHandling bool,
-		allowDroppingFKReferenced bool,
-		originalTables ...doltdb.TableName,
+	ctx context.Context,
+	skipFKHandling bool,
+	allowDroppingFKReferenced bool,
+	originalTables ...doltdb.TableName,
 ) (doltdb.RootValue, error) {
 	if len(originalTables) == 0 {
 		return root, nil

server/ast/drop_schema.go

@@ -28,7 +28,11 @@ func nodeDropSchema(ctx *Context, node *tree.DropSchema) (vitess.Statement, erro
 	}
 
 	if len(node.Names) > 1 {
-		return NotYetSupportedError("DROP SCHEMA with multiple schema names")
+		return NotYetSupportedError("DROP SCHEMA with multiple schema names is not yet supported.")
+	}
+
+	if node.DropBehavior == tree.DropCascade {
+		return NotYetSupportedError("DROP SCHEMA with CASCADE behavior is not yet supported.")
 	}
 
 	schemaName := node.Names[0]

server/ast/no_op.go

@@ -53,5 +53,5 @@ func NotYetSupportedError(errorMsg string) (vitess.Statement, error) {
 		return NewNoOp(errorMsg), nil
 	}
 
-	return nil, errors.New(errorMsg)
+	return nil, errors.Errorf(errorMsg + " Please file an issue at https://github.com/dolthub/doltgresql/issues")
 }

testing/go/schemas_test.go

@@ -874,7 +874,7 @@ var SchemaTests = []ScriptTest{
 		Focus: true,
 		SetUpScript: []string{
 			"CREATE SCHEMA dropme",
-			"CREATE schema hasTables",
+			`CREATE schema "hasTables"`,
 			"CREATE TABLE hasTables.t1 (pk BIGINT PRIMARY KEY, v1 BIGINT);",
 		},
 		Assertions: []ScriptTestAssertion{
@@ -893,9 +893,30 @@ var SchemaTests = []ScriptTest{
 				Query:    "DROP SCHEMA dropme;",
 				Expected: []sql.Row{},
 			},
+			{
+				Query: "Show schemas",
+				Expected: []sql.Row{
+					{"dolt"},
+					{"hasTables"},
+					{"pg_catalog"},
+					{"public"},
+					{"information_schema"},
+				},
+			},
 			{
 				Query:       "DROP SCHEMA dropme;",
-				ExpectedErr: "schema dropme does not exist",
+				ExpectedErr: "database schema not found",
+			},
+			{
+				Query: "drop schema if exists dropme;",
+			},
+			{
+				Query:       "DROP SCHEMA hasTables;",
+				ExpectedErr: "cannot drop schema hastables because other objects depend on it",
+			},
+			{
+				Skip:  true, // not implemented yet
+				Query: "drop schema hasTables cascade;",
 			},
 		},
 	},