Added IF EXISTS for DROP DATABASE command, #4659

CHANGELOG.md

@@ -30,6 +30,7 @@
 - [#4648](https://github.com/influxdb/influxdb/pull/4648): UDP Client (v2 client)
 - [#4690](https://github.com/influxdb/influxdb/pull/4690): SHOW SHARDS now includes database and policy. Thanks @pires
 - [#4676](https://github.com/influxdb/influxdb/pull/4676): UDP service listener performance enhancements
+- [#4659](https://github.com/influxdb/influxdb/pull/4659): Support IF EXISTS for DROP DATABASE
 
 ### Bugfixes
 - [#4643](https://github.com/influxdb/influxdb/pull/4643): Fix panic during backup restoration. Thanks @oiooj

cmd/influxd/run/server_test.go

@@ -78,6 +78,16 @@ func TestServer_DatabaseCommands(t *testing.T) {
 				command: `DROP DATABASE db1`,
 				exp:     `{"results":[{}]}`,
 			},
+			&Query{
+				name:    "drop database should error if it does not exists",
+				command: `DROP DATABASE db1`,
+				exp:     `{"results":[{"error":"database not found: db1"}]}`,
+			},
+			&Query{
+				name:    "drop database should not error with non-existing database db1 WITH IF EXISTS",
+				command: `DROP DATABASE IF EXISTS db1`,
+				exp:     `{"results":[{}]}`,
+			},
 			&Query{
 				name:    "show database should have no results",
 				command: `SHOW DATABASES`,

influxql/ast.go

@@ -340,12 +340,19 @@ func (s *CreateDatabaseStatement) RequiredPrivileges() ExecutionPrivileges {
 type DropDatabaseStatement struct {
 	// Name of the database to be dropped.
 	Name string
+
+	// IfExists indicates whether to return without error if the database
+	// does not exists.
+	IfExists bool
 }
 
 // String returns a string representation of the drop database statement.
 func (s *DropDatabaseStatement) String() string {
 	var buf bytes.Buffer
 	_, _ = buf.WriteString("DROP DATABASE ")
+	if s.IfExists {
+		_, _ = buf.WriteString("IF EXISTS ")
+	}
 	_, _ = buf.WriteString(s.Name)
 	return buf.String()
 }

influxql/parser.go

@@ -1458,6 +1458,16 @@ func (p *Parser) parseCreateDatabaseStatement() (*CreateDatabaseStatement, error
 func (p *Parser) parseDropDatabaseStatement() (*DropDatabaseStatement, error) {
 	stmt := &DropDatabaseStatement{}
 
+	// Look for "IF EXISTS"
+	if tok, _, _ := p.scanIgnoreWhitespace(); tok == IF {
+		if err := p.parseTokens([]Token{EXISTS}); err != nil {
+			return nil, err
+		}
+		stmt.IfExists = true
+	} else {
+		p.unscan()
+	}
+
 	// Parse the name of the database to be dropped.
 	lit, err := p.parseIdent()
 	if err != nil {

influxql/parser_test.go

@@ -1224,8 +1224,18 @@ func TestParser_ParseStatement(t *testing.T) {
 
 		// DROP DATABASE statement
 		{
-			s:    `DROP DATABASE testdb`,
-			stmt: &influxql.DropDatabaseStatement{Name: "testdb"},
+			s: `DROP DATABASE testdb`,
+			stmt: &influxql.DropDatabaseStatement{
+				Name:     "testdb",
+				IfExists: false,
+			},
+		},
+		{
+			s: `DROP DATABASE IF EXISTS testdb`,
+			stmt: &influxql.DropDatabaseStatement{
+				Name:     "testdb",
+				IfExists: true,
+			},
 		},
 
 		// DROP MEASUREMENT statement
@@ -1599,6 +1609,8 @@ func TestParser_ParseStatement(t *testing.T) {
 		{s: `CREATE DATABASE IF NOT`, err: `found EOF, expected EXISTS at line 1, char 24`},
 		{s: `CREATE DATABASE IF NOT EXISTS`, err: `found EOF, expected identifier at line 1, char 31`},
 		{s: `DROP DATABASE`, err: `found EOF, expected identifier at line 1, char 15`},
+		{s: `DROP DATABASE IF`, err: `found EOF, expected EXISTS at line 1, char 18`},
+		{s: `DROP DATABASE IF EXISTS`, err: `found EOF, expected identifier at line 1, char 25`},
 		{s: `DROP RETENTION`, err: `found EOF, expected POLICY at line 1, char 16`},
 		{s: `DROP RETENTION POLICY`, err: `found EOF, expected identifier at line 1, char 23`},
 		{s: `DROP RETENTION POLICY "1h.cpu"`, err: `found EOF, expected ON at line 1, char 31`},

tsdb/query_executor.go

@@ -370,6 +370,9 @@ func (q *QueryExecutor) executeDropDatabaseStatement(stmt *influxql.DropDatabase
 	if err != nil {
 		return &influxql.Result{Err: err}
 	} else if dbi == nil {
+		if stmt.IfExists {
+			return &influxql.Result{}
+		}
 		return &influxql.Result{Err: ErrDatabaseNotFound(stmt.Name)}
 	}