test: speed up ITDmlReturningTest

The initialization code for ITDmlReturningTest was borked and initialized
the database over and over again for each test method. This pushes Spanner
into throttling the DDL requests, which again makes both this and other
integration tests slow.

Updates #3247

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/it/ITDmlReturningTest.java

@@ -22,12 +22,13 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assume.assumeFalse;
 
 import com.google.cloud.spanner.AsyncResultSet;
 import com.google.cloud.spanner.AsyncResultSet.CallbackResponse;
+import com.google.cloud.spanner.DatabaseClient;
 import com.google.cloud.spanner.Dialect;
 import com.google.cloud.spanner.ErrorCode;
+import com.google.cloud.spanner.KeySet;
 import com.google.cloud.spanner.Mutation;
 import com.google.cloud.spanner.ParallelIntegrationTest;
 import com.google.cloud.spanner.ResultSet;
@@ -39,15 +40,15 @@
 import com.google.cloud.spanner.connection.StatementResult;
 import com.google.cloud.spanner.connection.StatementResult.ResultType;
 import com.google.cloud.spanner.connection.TransactionMode;
-import com.google.cloud.spanner.testing.EmulatorSpannerHelper;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executors;
 import org.junit.Before;
@@ -81,12 +82,7 @@ public class ITDmlReturningTest extends ITAbstractSpannerTest {
               + "  SingerId BIGINT PRIMARY KEY,"
               + "  FirstName character varying(1024),"
               + "  LastName character varying(1024))");
-  private final Map<Dialect, Boolean> IS_INITIALIZED = new HashMap<>();
-
-  public ITDmlReturningTest() {
-    IS_INITIALIZED.put(Dialect.GOOGLE_STANDARD_SQL, false);
-    IS_INITIALIZED.put(Dialect.POSTGRESQL, false);
-  }
+  private static final Set<Dialect> IS_INITIALIZED = new HashSet<>();
 
   @Parameter public Dialect dialect;
 
@@ -96,41 +92,34 @@ public static Object[] data() {
   }
 
   private boolean checkAndSetInitialized() {
-    if ((dialect == Dialect.GOOGLE_STANDARD_SQL) && !IS_INITIALIZED.get(dialect)) {
-      IS_INITIALIZED.put(dialect, true);
-      return true;
-    }
-    if ((dialect == Dialect.POSTGRESQL) && !IS_INITIALIZED.get(dialect)) {
-      IS_INITIALIZED.put(dialect, true);
-      return true;
-    }
-    return false;
+    return !IS_INITIALIZED.add(dialect);
   }
 
   @Before
   public void setupTable() {
-    assumeFalse(
-        "DML Returning is not supported in the emulator", EmulatorSpannerHelper.isUsingEmulator());
-    if (checkAndSetInitialized()) {
+    if (!checkAndSetInitialized()) {
       database =
           env.getTestHelper()
               .createTestDatabase(dialect, Collections.singleton(DDL_MAP.get(dialect)));
-      List<String> firstNames = Arrays.asList("ABC", "ABC", "DEF", "PQR", "ABC");
-      List<String> lastNames = Arrays.asList("XYZ", "DEF", "XYZ", "ABC", "GHI");
-      List<Mutation> mutations = new ArrayList<>();
-      for (int id = 1; id <= 5; id++) {
-        mutations.add(
-            Mutation.newInsertBuilder("SINGERS")
-                .set("SINGERID")
-                .to(id)
-                .set("FIRSTNAME")
-                .to(firstNames.get(id - 1))
-                .set("LASTNAME")
-                .to(lastNames.get(id - 1))
-                .build());
-      }
-      env.getTestHelper().getDatabaseClient(database).write(mutations);
     }
+    DatabaseClient client = env.getTestHelper().getDatabaseClient(database);
+    client.write(ImmutableList.of(Mutation.delete("SINGERS", KeySet.all())));
+
+    List<String> firstNames = Arrays.asList("ABC", "ABC", "DEF", "PQR", "ABC");
+    List<String> lastNames = Arrays.asList("XYZ", "DEF", "XYZ", "ABC", "GHI");
+    List<Mutation> mutations = new ArrayList<>();
+    for (int id = 1; id <= 5; id++) {
+      mutations.add(
+          Mutation.newInsertBuilder("SINGERS")
+              .set("SINGERID")
+              .to(id)
+              .set("FIRSTNAME")
+              .to(firstNames.get(id - 1))
+              .set("LASTNAME")
+              .to(lastNames.get(id - 1))
+              .build());
+    }
+    env.getTestHelper().getDatabaseClient(database).write(mutations);
   }
 
   @Test
@@ -211,9 +200,9 @@ public void testDmlReturningExecuteUpdateAsync() {
   public void testDmlReturningExecuteBatchUpdate() {
     try (Connection connection = createConnection()) {
       connection.setAutocommit(false);
-      final Statement UPDATE_STMT = UPDATE_RETURNING_MAP.get(dialect);
+      final Statement updateStmt = Preconditions.checkNotNull(UPDATE_RETURNING_MAP.get(dialect));
       long[] counts =
-          connection.executeBatchUpdate(ImmutableList.of(UPDATE_STMT, UPDATE_STMT, UPDATE_STMT));
+          connection.executeBatchUpdate(ImmutableList.of(updateStmt, updateStmt, updateStmt));
       assertArrayEquals(counts, new long[] {3, 3, 3});
     }
   }
@@ -222,10 +211,10 @@ public void testDmlReturningExecuteBatchUpdate() {
   public void testDmlReturningExecuteBatchUpdateAsync() {
     try (Connection connection = createConnection()) {
       connection.setAutocommit(false);
-      final Statement UPDATE_STMT = UPDATE_RETURNING_MAP.get(dialect);
+      final Statement updateStmt = Preconditions.checkNotNull(UPDATE_RETURNING_MAP.get(dialect));
       long[] counts =
           connection
-              .executeBatchUpdateAsync(ImmutableList.of(UPDATE_STMT, UPDATE_STMT, UPDATE_STMT))
+              .executeBatchUpdateAsync(ImmutableList.of(updateStmt, updateStmt, updateStmt))
               .get();
       assertArrayEquals(counts, new long[] {3, 3, 3});
     } catch (ExecutionException | InterruptedException e) {