Bug fix for db.Ping(ctx) against a Doltgres server

Author: fulghum

server/doltgres_handler.go

@@ -230,7 +230,16 @@ func (h *DoltgresHandler) doQuery(ctx context.Context, c *mysql.Conn, query stri
 		}
 	}()
 
-	schema, rowIter, qFlags, err := queryExec(sqlCtx, query, parsed, analyzedPlan)
+	var schema sql.Schema
+	var rowIter sql.RowIter
+	var qFlags *sql.QueryFlags
+	if parsed == nil && analyzedPlan == nil {
+		// If the query parsed to a nil parse tree and a nil analyzed plan, then there's nothing to execute
+		logrus.Debugf("nothing to execute for query: %s", query)
+		rowIter = sql.RowsToRowIter()
+	} else {
+		schema, rowIter, qFlags, err = queryExec(sqlCtx, query, parsed, analyzedPlan)
+	}
 	if err != nil {
 		if printErrorStackTraces {
 			fmt.Printf("error running query: %+v\n", err)

testing/go/framework.go

@@ -130,6 +130,7 @@ func RunScript(t *testing.T, script ScriptTest, normalizeRows bool) {
 			Default: pgxConn,
 			Current: pgxConn,
 		}
+		require.NoError(t, pgxConn.Ping(ctx))
 		defer func() {
 			conn.Close(ctx)
 		}()
@@ -309,6 +310,9 @@ func CreateServer(t *testing.T, database string) (context.Context, *Connection,
 
 	conn, err := pgx.Connect(ctx, fmt.Sprintf("postgres://postgres:[email protected]:%d/%s", port, database))
 	require.NoError(t, err)
+
+	// Ping the connection to test that it's alive, and also to test that Doltgres handles empty queries correctly
+	require.NoError(t, conn.Ping(ctx))
 	return ctx, &Connection{
 		Default: conn,
 		Current: conn,

testing/go/smoke_test.go

@@ -71,6 +71,18 @@ func TestSmokeTests(t *testing.T) {
 					Query:    "SELECT NULL = NULL",
 					Expected: []sql.Row{{nil}},
 				},
+				{
+					Query:    ";",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    " ; ",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "-- this is only a comment",
+					Expected: []sql.Row{},
+				},
 			},
 		},
 		{