Fix reading from Delta in a transaction

Delta connector supports write in autocommit mode only, but it should
allow multiple reads in a transaction (e.g. reading from Delta and
writing to Hive connector).

The commit removes the check from `DeltaLakeConnector` since appropriate
check is being done in `InMemoryTransactionManager`.

plugin/trino-delta-lake/src/main/java/io/trino/plugin/deltalake/DeltaLakeConnector.java

@@ -40,7 +40,6 @@
 import java.util.Optional;
 import java.util.Set;
 
-import static com.google.common.base.Verify.verify;
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static io.trino.spi.transaction.IsolationLevel.READ_COMMITTED;
 import static io.trino.spi.transaction.IsolationLevel.checkConnectorSupports;
@@ -193,7 +192,6 @@ public Iterable<EventListener> getEventListeners()
     public ConnectorTransactionHandle beginTransaction(IsolationLevel isolationLevel, boolean readOnly, boolean autoCommit)
     {
         checkConnectorSupports(READ_COMMITTED, isolationLevel);
-        verify(autoCommit, "Catalog only supports writes using autocommit: DeltaLake");
         ConnectorTransactionHandle transaction = new HiveTransactionHandle(true);
         transactionManager.begin(transaction);
         return transaction;

testing/trino-testing/src/main/java/io/trino/testing/BaseConnectorTest.java

@@ -493,6 +493,16 @@ public void testSelectAll()
         assertQuery("SELECT * FROM orders");
     }
 
+    @Test
+    public void testSelectInTransaction()
+    {
+        inTransaction(session -> {
+            assertQuery(session, "SELECT nationkey, name, regionkey FROM nation");
+            assertQuery(session, "SELECT regionkey, name FROM region");
+            assertQuery(session, "SELECT nationkey, name, regionkey FROM nation");
+        });
+    }
+
     /**
      * Test interactions between optimizer (including CBO), scheduling and connector metadata APIs.
      */