add if not exists option to create view

Author: James Cor

enginetest/queries/view_queries.go

@@ -20,6 +20,36 @@ import (
 )
 
 var ViewScripts = []ScriptTest{
+	{
+		Name: "existing views",
+		SetUpScript: []string{
+			"create view v as select 1;",
+			"create table t (i int);",
+			"insert into t values (1);",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Query: "create if not exists view v as select 2;",
+				Expected: []sql.Row{
+					{types.NewOkResult(0)},
+				},
+			},
+			{
+				Query:    "select * from v;",
+				Expected: []sql.Row{{1}},
+			},
+			{
+				Query: "create if not exists view t as select 2;",
+				Expected: []sql.Row{
+					{types.NewOkResult(0)},
+				},
+			},
+			{
+				Query:    "select * from t;",
+				Expected: []sql.Row{{1}},
+			},
+		},
+	},
 	{
 		Name: "multi database view",
 		SetUpScript: []string{

memory/database.go

@@ -555,7 +555,7 @@ func (d *Database) Database() *BaseDatabase {
 func (d *Database) CreateView(ctx *sql.Context, name string, selectStatement, createViewStmt string) error {
 	_, ok := d.views[strings.ToLower(name)]
 	if ok {
-		return sql.ErrExistingView.New(name)
+		return sql.ErrExistingView.New(d.Name(), name)
 	}
 
 	sqlMode := sql.LoadSqlMode(ctx)

sql/plan/create_view.go

@@ -31,6 +31,7 @@ type CreateView struct {
 	database         sql.Database
 	targetSchema     sql.Schema
 	Name             string
+	IfNotExists      bool
 	IsReplace        bool
 	Definition       *SubqueryAlias
 	CreateViewString string
@@ -46,11 +47,12 @@ var _ sql.SchemaTarget = (*CreateView)(nil)
 
 // NewCreateView creates a CreateView node with the specified parameters,
 // setting its catalog to nil.
-func NewCreateView(database sql.Database, name string, definition *SubqueryAlias, isReplace bool, createViewStr, algorithm, definer, security string) *CreateView {
+func NewCreateView(database sql.Database, name string, definition *SubqueryAlias, ifNotExists, isReplace bool, createViewStr, algorithm, definer, security string) *CreateView {
 	return &CreateView{
 		UnaryNode:        UnaryNode{Child: definition},
 		database:         database,
 		Name:             name,
+		IfNotExists:      ifNotExists,
 		IsReplace:        isReplace,
 		Definition:       definition,
 		CreateViewString: createViewStr,

sql/planbuilder/create_ddl.go

@@ -672,7 +672,7 @@ func (b *Builder) buildCreateView(inScope *scope, subQuery string, fullQuery str
 	if !ok {
 		b.handleErr(sql.ErrDatabaseSchemaNotFound.New(c.Table.SchemaQualifier.String()))
 	}
-	createView := plan.NewCreateView(db, c.ViewSpec.ViewName.Name.String(), queryAlias, c.OrReplace, subQuery, c.ViewSpec.Algorithm, definer, c.ViewSpec.Security)
+	createView := plan.NewCreateView(db, c.ViewSpec.ViewName.Name.String(), queryAlias, c.IfNotExists, c.OrReplace, subQuery, c.ViewSpec.Algorithm, definer, c.ViewSpec.Security)
 	outScope.node = b.modifySchemaTarget(queryScope, createView, createView.Definition.Schema())
 
 	return outScope

sql/rowexec/create_view_test.go

@@ -27,7 +27,7 @@ import (
 	"github.com/dolthub/go-mysql-server/sql/types"
 )
 
-func newCreateView(db memory.MemoryDatabase, isReplace bool) *plan.CreateView {
+func newCreateView(db memory.MemoryDatabase, ifNotExists, isReplace bool) *plan.CreateView {
 	table := memory.NewTable(db.Database(), "mytable", sql.NewPrimaryKeySchema(sql.Schema{
 		{Name: "i", Source: "mytable", Type: types.Int32},
 		{Name: "s", Source: "mytable", Type: types.Text},
@@ -44,7 +44,7 @@ func newCreateView(db memory.MemoryDatabase, isReplace bool) *plan.CreateView {
 		),
 	)
 
-	createView := plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, isReplace, "CREATE VIEW myview AS SELECT i FROM mytable", "", "", "")
+	createView := plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, ifNotExists, isReplace, "CREATE VIEW myview AS SELECT i FROM mytable", "", "", "")
 
 	return createView
 }
@@ -54,7 +54,7 @@ func newCreateView(db memory.MemoryDatabase, isReplace bool) *plan.CreateView {
 func TestCreateViewWithRegistry(t *testing.T) {
 	require := require.New(t)
 
-	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false)
+	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false, false)
 
 	ctx := sql.NewContext(context.Background())
 	_, err := DefaultBuilder.buildNodeExec(ctx, createView, nil)
@@ -68,7 +68,8 @@ func TestCreateViewWithRegistry(t *testing.T) {
 
 // Tests that CreateView RowIter returns an error when the view exists
 func TestCreateExistingViewNative(t *testing.T) {
-	createView := newCreateView(memory.NewDatabase("mydb"), false)
+	createView := newCreateView(memory.NewDatabase("mydb"), false, false)
+	createExistingView := newCreateView(memory.NewDatabase("mydb"), true, false)
 
 	ctx := sql.NewContext(context.Background())
 	_, err := DefaultBuilder.buildNodeExec(ctx, createView, nil)
@@ -78,13 +79,17 @@ func TestCreateExistingViewNative(t *testing.T) {
 	_, err = DefaultBuilder.buildNodeExec(ctx, createView, nil)
 	require.Error(t, err)
 	require.True(t, sql.ErrExistingView.Is(err))
+
+	ctx = sql.NewContext(context.Background())
+	_, err = DefaultBuilder.buildNodeExec(ctx, createExistingView, nil)
+	require.NoError(t, err)
 }
 
 // Tests that CreateView RowIter succeeds when the view exists and the
 // IsReplace flag is set to true
 func TestReplaceExistingViewNative(t *testing.T) {
 	db := memory.NewDatabase("mydb")
-	createView := newCreateView(db, false)
+	createView := newCreateView(db, false, false)
 
 	ctx := sql.NewContext(context.Background())
 	_, err := DefaultBuilder.buildNodeExec(ctx, createView, nil)
@@ -110,7 +115,7 @@ func TestReplaceExistingViewNative(t *testing.T) {
 		),
 	)
 
-	createView = plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, true, "CREATE VIEW myview AS SELECT i + 1 FROM mytable", "", "", "")
+	createView = plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, false, true, "CREATE VIEW myview AS SELECT i + 1 FROM mytable", "", "", "")
 	_, err = DefaultBuilder.buildNodeExec(ctx, createView, nil)
 	require.NoError(t, err)
 
@@ -124,7 +129,7 @@ func TestReplaceExistingViewNative(t *testing.T) {
 // the catalog when RowIter is called
 func TestCreateViewNative(t *testing.T) {
 	db := memory.NewDatabase("mydb")
-	createView := newCreateView(db, false)
+	createView := newCreateView(db, false, false)
 
 	ctx := sql.NewContext(context.Background())
 	_, err := DefaultBuilder.buildNodeExec(ctx, createView, nil)
@@ -141,7 +146,7 @@ func TestCreateViewNative(t *testing.T) {
 func TestCreateExistingViewWithRegistry(t *testing.T) {
 	require := require.New(t)
 
-	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false)
+	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false, false)
 
 	view := createView.View()
 	viewReg := sql.NewViewRegistry()
@@ -161,7 +166,7 @@ func TestCreateExistingViewWithRegistry(t *testing.T) {
 func TestReplaceExistingViewWithRegistry(t *testing.T) {
 	require := require.New(t)
 
-	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false)
+	createView := newCreateView(memory.NewViewlessDatabase("mydb"), false, false)
 
 	view := sql.NewView(createView.Name, nil, "", "")
 	viewReg := sql.NewViewRegistry()

sql/rowexec/ddl.go

@@ -164,19 +164,32 @@ func (b *BaseBuilder) buildCreateView(ctx *sql.Context, n *plan.CreateView, row
 		return nil, err
 	}
 	for _, name := range names {
-		if strings.ToLower(name) == strings.ToLower(n.Name) {
-			return nil, sql.ErrTableAlreadyExists.New(n)
+		if !strings.EqualFold(name, n.Name) {
+			continue
+		}
+		if n.IfNotExists {
+			return rowIterWithOkResultWithZeroRowsAffected(), nil
 		}
+		return nil, sql.ErrTableAlreadyExists.New(n)
 	}
 
 	// TODO: isUpdatable should be defined at CREATE VIEW time
 	// isUpdatable := GetIsUpdatableFromCreateView(cv)
 	creator, ok := n.Database().(sql.ViewDatabase)
-	if ok {
-		return rowIterWithOkResultWithZeroRowsAffected(), creator.CreateView(ctx, n.Name, n.Definition.TextDefinition, n.CreateViewString)
-	} else {
-		return rowIterWithOkResultWithZeroRowsAffected(), registry.Register(n.Database().Name(), n.View())
+	if !ok {
+		err = registry.Register(n.Database().Name(), n.View())
+		if err != nil {
+			return nil, err
+		}
+		return rowIterWithOkResultWithZeroRowsAffected(), nil
 	}
+	err = creator.CreateView(ctx, n.Name, n.Definition.TextDefinition, n.CreateViewString)
+	if err != nil {
+		if !sql.ErrExistingView.Is(err) || !n.IfNotExists {
+			return nil, err
+		}
+	}
+	return rowIterWithOkResultWithZeroRowsAffected(), nil
 }
 
 func (b *BaseBuilder) buildCreateCheck(ctx *sql.Context, n *plan.CreateCheck, row sql.Row) (sql.RowIter, error) {

sql/rowexec/drop_view_test.go

@@ -47,7 +47,7 @@ func setupView(t *testing.T, db memory.MemoryDatabase) (*sql.Context, *sql.View)
 		),
 	)
 
-	createView := plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, false, "CREATE VIEW myview AS SELECT i FROM mytable", "", "", "")
+	createView := plan.NewCreateView(db, subqueryAlias.Name(), subqueryAlias, false, false, "CREATE VIEW myview AS SELECT i FROM mytable", "", "", "")
 
 	ctx := sql.NewContext(context.Background())