Implement server side cursors

go/mysql/conn_test.go

@@ -79,6 +79,7 @@ func createSocketPair(t *testing.T) (net.Listener, *Conn, *Conn) {
 	cConn := newConn(clientConn, DefaultFlushDelay, 0)
 	sConn := newConn(serverConn, DefaultFlushDelay, 0)
 	sConn.PrepareData = map[uint32]*PrepareData{}
+	sConn.cursorStates = map[uint32]*CursorState{}
 
 	return listener, sConn, cConn
 }
@@ -856,9 +857,9 @@ func TestEmptyQuery(t *testing.T) {
 			// The queries run will be an empty query; Even with the empty error, the connection should be fine
 			require.True(t, res, "we should not break the connection in case of no errors")
 			// Read the result and assert that we indeed see the error for empty query.
-			data, more, _, err := cConn.ReadQueryResult(100, true)
+			data, status, _, err := cConn.ReadQueryResult(100, true)
 			require.EqualError(t, err, "Query was empty (errno 1065) (sqlstate 42000)")
-			require.False(t, more)
+			require.False(t, IsMoreResultsExists(status))
 			require.Nil(t, data)
 		})
 	}
@@ -886,17 +887,17 @@ func TestMultiStatement(t *testing.T) {
 			// The queries run will be select 1; and select 2; These queries do not return any errors, so the connection should still be open
 			require.True(t, res, "we should not break the connection in case of no errors")
 			// Read the result of the query and assert that it is indeed what we want. This will contain the result of the first query.
-			data, more, _, err := cConn.ReadQueryResult(100, true)
+			data, status, _, err := cConn.ReadQueryResult(100, true)
 			require.NoError(t, err)
 			// Since we executed 2 queries, there should be more results to be read
-			require.True(t, more)
+			require.True(t, IsMoreResultsExists(status))
 			require.True(t, data.Equal(selectRowsResult))
 
 			// Read the results for the second query and verify the correctness
-			data, more, _, err = cConn.ReadQueryResult(100, true)
+			data, status, _, err = cConn.ReadQueryResult(100, true)
 			require.NoError(t, err)
 			// This was the final query run, so we expect that more should be false as there are no more queries.
-			require.False(t, more)
+			require.False(t, IsMoreResultsExists(status))
 			require.True(t, data.Equal(selectRowsResult))
 
 			// This time we run two queries fist of which will return an error
@@ -908,10 +909,10 @@ func TestMultiStatement(t *testing.T) {
 			require.True(t, res, "we should not break the connection because of execution errors")
 
 			// Read the result and assert that we indeed see the error that testRun throws.
-			data, more, _, err = cConn.ReadQueryResult(100, true)
+			data, status, _, err = cConn.ReadQueryResult(100, true)
 			require.EqualError(t, err, "cannot get column number (errno 2027) (sqlstate HY000)")
 			// In case of errors in a multi-statement, the following statements are not executed, therefore we want that more should be false
-			require.False(t, more)
+			require.False(t, IsMoreResultsExists(status))
 			require.Nil(t, data)
 		})
 	}

go/mysql/constants.go

@@ -156,7 +156,8 @@ const (
 
 // Status flags. They are returned by the server in a few cases.
 // Originally found in include/mysql/mysql_com.h
-// See http://dev.mysql.com/doc/internals/en/status-flags.html
+// See https://dev.mysql.com/doc/dev/mysql-server/latest/mysql__com_8h.html#a1d854e841086925be1883e4d7b4e8cad
+// and https://mariadb.com/kb/en/ok_packet/#server-status-flag
 const (
 	// a transaction is active
 	ServerStatusInTrans   uint16 = 0x0001
@@ -183,6 +184,21 @@ const (
 	ServerSessionStateChanged uint16 = 0x4000
 )
 
+// Helper for checking if SERVER_MORE_RESULTS_EXISTS is set
+func IsMoreResultsExists(status uint16) bool {
+	return status&ServerMoreResultsExists == ServerMoreResultsExists
+}
+
+// Cursor Types. They are received on COM_STMT_EXECUTE()
+// See https://dev.mysql.com/doc/dev/mysql-server/latest/mysql__com_8h.html#a3e5e9e744ff6f7b989a604fd669977da
+// and https://mariadb.com/kb/en/com_stmt_execute/#flag
+const (
+	CursorTypeNoCursor = iota
+	CursorTypeReadOnly
+	CursorTypeCursorForUpdate
+	CursorTypeScrollableCursor
+)
+
 // State Change Information
 const (
 	// one or more system variables changed.

go/mysql/endtoend/client_test.go

@@ -161,29 +161,29 @@ func doTestMultiResult(t *testing.T, disableClientDeprecateEOF bool) {
 	expectNoError(t, err)
 	defer conn.Close()
 
-	qr, more, err := conn.ExecuteFetchMulti("select 1 from dual; set autocommit=1; select 1 from dual", 10, true)
+	qr, status, err := conn.ExecuteFetchMulti("select 1 from dual; set autocommit=1; select 1 from dual", 10, true)
 	expectNoError(t, err)
-	expectFlag(t, "ExecuteMultiFetch(multi result)", more, true)
+	expectFlag(t, "ExecuteMultiFetch(multi result)", mysql.IsMoreResultsExists(status), true)
 	assert.EqualValues(t, 1, len(qr.Rows))
 
-	qr, more, _, err = conn.ReadQueryResult(10, true)
+	qr, status, _, err = conn.ReadQueryResult(10, true)
 	expectNoError(t, err)
-	expectFlag(t, "ReadQueryResult(1)", more, true)
+	expectFlag(t, "ReadQueryResult(1)", mysql.IsMoreResultsExists(status), true)
 	assert.EqualValues(t, 0, len(qr.Rows))
 
-	qr, more, _, err = conn.ReadQueryResult(10, true)
+	qr, status, _, err = conn.ReadQueryResult(10, true)
 	expectNoError(t, err)
-	expectFlag(t, "ReadQueryResult(2)", more, false)
+	expectFlag(t, "ReadQueryResult(2)", mysql.IsMoreResultsExists(status), false)
 	assert.EqualValues(t, 1, len(qr.Rows))
 
-	qr, more, err = conn.ExecuteFetchMulti("select 1 from dual", 10, true)
+	qr, status, err = conn.ExecuteFetchMulti("select 1 from dual", 10, true)
 	expectNoError(t, err)
-	expectFlag(t, "ExecuteMultiFetch(single result)", more, false)
+	expectFlag(t, "ExecuteMultiFetch(single result)", mysql.IsMoreResultsExists(status), false)
 	assert.EqualValues(t, 1, len(qr.Rows))
 
-	qr, more, err = conn.ExecuteFetchMulti("set autocommit=1", 10, true)
+	qr, status, err = conn.ExecuteFetchMulti("set autocommit=1", 10, true)
 	expectNoError(t, err)
-	expectFlag(t, "ExecuteMultiFetch(no result)", more, false)
+	expectFlag(t, "ExecuteMultiFetch(no result)", mysql.IsMoreResultsExists(status), false)
 	assert.EqualValues(t, 0, len(qr.Rows))
 
 	// The ClientDeprecateEOF protocol change has a subtle twist in which an EOF or OK
@@ -212,19 +212,19 @@ func doTestMultiResult(t *testing.T, disableClientDeprecateEOF bool) {
 	err = conn.ExecuteFetchMultiDrain("update a set name = concat(name, ', multi drain 1'); select * from a; select count(*) from a")
 	expectNoError(t, err)
 	// If the previous command leaves packet in invalid state, this will fail.
-	qr, more, err = conn.ExecuteFetchMulti("update a set name = concat(name, ', fetch multi'); select * from a; select count(*) from a", 300, true)
+	qr, status, err = conn.ExecuteFetchMulti("update a set name = concat(name, ', fetch multi'); select * from a; select count(*) from a", 300, true)
 	expectNoError(t, err)
-	expectFlag(t, "ExecuteMultiFetch(multi result)", more, true)
+	expectFlag(t, "ExecuteMultiFetch(multi result)", mysql.IsMoreResultsExists(status), true)
 	assert.EqualValues(t, 255, qr.RowsAffected)
 
-	qr, more, _, err = conn.ReadQueryResult(300, true)
+	qr, status, _, err = conn.ReadQueryResult(300, true)
 	expectNoError(t, err)
-	expectFlag(t, "ReadQueryResult(1)", more, true)
+	expectFlag(t, "ReadQueryResult(1)", mysql.IsMoreResultsExists(status), true)
 	assert.EqualValues(t, 255, len(qr.Rows), "ReadQueryResult(1)")
 
-	qr, more, _, err = conn.ReadQueryResult(300, true)
+	qr, status, _, err = conn.ReadQueryResult(300, true)
 	expectNoError(t, err)
-	expectFlag(t, "ReadQueryResult(2)", more, false)
+	expectFlag(t, "ReadQueryResult(2)", mysql.IsMoreResultsExists(status), false)
 	assert.EqualValues(t, 1, len(qr.Rows), "ReadQueryResult(1)")
 
 	// Verify that a ExecuteFetchMultiDrain is happy to operate again after all the above.

go/mysql/mysql_fuzzer.go

@@ -199,6 +199,7 @@ func FuzzHandleNextCommand(data []byte) int {
 		queryPacket: data,
 	}, DefaultFlushDelay, 0, false)
 	sConn.PrepareData = map[uint32]*PrepareData{}
+	sConn.cursorStates = map[uint32]*CursorState{}
 
 	handler := &fuzztestRun{}
 	_ = sConn.handleNextCommand(handler)