feat: support isolation level REPEATABLE_READ for R/W transactions

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractReadContext.java

@@ -641,8 +641,8 @@ private ResultSet executeQueryInternal(
    *   <li>Specific {@link QueryOptions} passed in for this query.
    *   <li>Any value specified in a valid environment variable when the {@link SpannerOptions}
    *       instance was created.
-   *   <li>The default {@link SpannerOptions#getDefaultQueryOptions()} specified for the database
-   *       where the query is executed.
+   *   <li>The default {@link SpannerOptions#getDefaultQueryOptions(DatabaseId)} ()} specified for
+   *       the database where the query is executed.
    * </ol>
    */
   @VisibleForTesting

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseClient.java

@@ -22,6 +22,7 @@
 import com.google.cloud.spanner.Options.TransactionOption;
 import com.google.cloud.spanner.Options.UpdateOption;
 import com.google.spanner.v1.BatchWriteResponse;
+import com.google.spanner.v1.TransactionOptions.IsolationLevel;
 
 /**
  * Interface for all the APIs that are used to read/write data into a Cloud Spanner database. An
@@ -414,6 +415,7 @@ ServerStream<BatchWriteResponse> batchWriteAtLeastOnce(
    *       applied to any other requests on the transaction.
    *   <li>{@link Options#commitStats()}: Request that the server includes commit statistics in the
    *       {@link CommitResponse}.
+   *   <li>{@link Options#isolationLevel(IsolationLevel)}: The isolation level for the transaction
    * </ul>
    */
   TransactionRunner readWriteTransaction(TransactionOption... options);
@@ -454,6 +456,7 @@ ServerStream<BatchWriteResponse> batchWriteAtLeastOnce(
    *       applied to any other requests on the transaction.
    *   <li>{@link Options#commitStats()}: Request that the server includes commit statistics in the
    *       {@link CommitResponse}.
+   *   <li>{@link Options#isolationLevel(IsolationLevel)}: The isolation level for the transaction
    * </ul>
    */
   TransactionManager transactionManager(TransactionOption... options);
@@ -494,6 +497,7 @@ ServerStream<BatchWriteResponse> batchWriteAtLeastOnce(
    *       applied to any other requests on the transaction.
    *   <li>{@link Options#commitStats()}: Request that the server includes commit statistics in the
    *       {@link CommitResponse}.
+   *   <li>{@link Options#isolationLevel(IsolationLevel)}: The isolation level for the transaction
    * </ul>
    */
   AsyncRunner runAsync(TransactionOption... options);
@@ -548,6 +552,7 @@ ServerStream<BatchWriteResponse> batchWriteAtLeastOnce(
    *       applied to any other requests on the transaction.
    *   <li>{@link Options#commitStats()}: Request that the server includes commit statistics in the
    *       {@link CommitResponse}.
+   *   <li>{@link Options#isolationLevel(IsolationLevel)}: The isolation level for the transaction
    * </ul>
    */
   AsyncTransactionManager transactionManagerAsync(TransactionOption... options);

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Options.java

@@ -21,6 +21,7 @@
 import com.google.spanner.v1.ReadRequest.LockHint;
 import com.google.spanner.v1.ReadRequest.OrderBy;
 import com.google.spanner.v1.RequestOptions.Priority;
+import com.google.spanner.v1.TransactionOptions.IsolationLevel;
 import java.io.Serializable;
 import java.time.Duration;
 import java.util.Objects;
@@ -159,6 +160,13 @@ public static TransactionOption optimisticLock() {
     return OPTIMISTIC_LOCK_OPTION;
   }
 
+  /**
+   * Specifying this instructs the transaction to request {@link IsolationLevel} from the backend.
+   */
+  public static TransactionOption isolationLevel(IsolationLevel isolationLevel) {
+    return new IsolationLevelOption(isolationLevel);
+  }
+
   /**
    * Specifying this instructs the transaction to be excluded from being recorded in change streams
    * with the DDL option `allow_txn_exclusion=true`. This does not exclude the transaction from
@@ -490,6 +498,20 @@ void appendToOptions(Options options) {
     }
   }
 
+  /** Option to set isolation level for read/write transactions. */
+  static final class IsolationLevelOption extends InternalOption implements TransactionOption {
+    private final IsolationLevel isolationLevel;
+
+    public IsolationLevelOption(IsolationLevel isolationLevel) {
+      this.isolationLevel = isolationLevel;
+    }
+
+    @Override
+    void appendToOptions(Options options) {
+      options.isolationLevel = isolationLevel;
+    }
+  }
+
   private boolean withCommitStats;
 
   private Duration maxCommitDelay;
@@ -512,6 +534,7 @@ void appendToOptions(Options options) {
   private RpcOrderBy orderBy;
   private RpcLockHint lockHint;
   private Boolean lastStatement;
+  private IsolationLevel isolationLevel;
 
   // Construction is via factory methods below.
   private Options() {}
@@ -664,6 +687,10 @@ LockHint lockHint() {
     return lockHint == null ? null : lockHint.proto;
   }
 
+  IsolationLevel isolationLevel() {
+    return isolationLevel;
+  }
+
   @Override
   public String toString() {
     StringBuilder b = new StringBuilder();
@@ -726,6 +753,9 @@ public String toString() {
     if (lockHint != null) {
       b.append("lockHint: ").append(lockHint).append(' ');
     }
+    if (isolationLevel != null) {
+      b.append("isolationLevel: ").append(isolationLevel).append(' ');
+    }
     return b.toString();
   }
 
@@ -767,7 +797,8 @@ public boolean equals(Object o) {
         && Objects.equals(directedReadOptions(), that.directedReadOptions())
         && Objects.equals(orderBy(), that.orderBy())
         && Objects.equals(isLastStatement(), that.isLastStatement())
-        && Objects.equals(lockHint(), that.lockHint());
+        && Objects.equals(lockHint(), that.lockHint())
+        && Objects.equals(isolationLevel(), that.isolationLevel());
   }
 
   @Override
@@ -833,6 +864,9 @@ public int hashCode() {
     if (lockHint != null) {
       result = 31 * result + lockHint.hashCode();
     }
+    if (isolationLevel != null) {
+      result = 31 * result + isolationLevel.hashCode();
+    }
     return result;
   }
 

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionImpl.java

@@ -83,6 +83,9 @@ static TransactionOptions createReadWriteTransactionOptions(
         && previousTransactionId != com.google.protobuf.ByteString.EMPTY) {
       readWrite.setMultiplexedSessionPreviousTransactionId(previousTransactionId);
     }
+    if (options.isolationLevel() != null) {
+      transactionOptions.setIsolationLevel(options.isolationLevel());
+    }
     transactionOptions.setReadWrite(readWrite);
     return transactionOptions.build();
   }
@@ -193,6 +196,10 @@ void markUsed(Instant instant) {
     sessionReference.markUsed(instant);
   }
 
+  TransactionOptions defaultTransactionOptions() {
+    return this.spanner.getOptions().getDefaultTransactionOptions();
+  }
+
   public DatabaseId getDatabaseId() {
     return sessionReference.getDatabaseId();
   }
@@ -252,7 +259,11 @@ public CommitResponse writeAtLeastOnceWithOptions(
     if (options.withExcludeTxnFromChangeStreams() == Boolean.TRUE) {
       transactionOptionsBuilder.setExcludeTxnFromChangeStreams(true);
     }
-    requestBuilder.setSingleUseTransaction(transactionOptionsBuilder);
+    if (options.isolationLevel() != null) {
+      transactionOptionsBuilder.setIsolationLevel(options.isolationLevel());
+    }
+    requestBuilder.setSingleUseTransaction(
+        defaultTransactionOptions().toBuilder().mergeFrom(transactionOptionsBuilder.build()));
 
     if (options.hasMaxCommitDelay()) {
       requestBuilder.setMaxCommitDelay(
@@ -444,7 +455,11 @@ ApiFuture<Transaction> beginTransactionAsync(
         BeginTransactionRequest.newBuilder()
             .setSession(getName())
             .setOptions(
-                createReadWriteTransactionOptions(transactionOptions, previousTransactionId));
+                defaultTransactionOptions()
+                    .toBuilder()
+                    .mergeFrom(
+                        createReadWriteTransactionOptions(
+                            transactionOptions, previousTransactionId)));
     if (sessionReference.getIsMultiplexed() && mutation != null) {
       requestBuilder.setMutationKey(mutation);
     }
@@ -489,7 +504,6 @@ TransactionContextImpl newTransaction(Options options, ByteString previousTransa
         .setOptions(options)
         .setTransactionId(null)
         .setPreviousTransactionId(previousTransactionId)
-        .setOptions(options)
         .setTrackTransactionStarter(spanner.getOptions().isTrackTransactionStarter())
         .setRpc(spanner.getRpc())
         .setDefaultQueryOptions(spanner.getDefaultQueryOptions(getDatabaseId()))

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java

@@ -66,6 +66,8 @@
 import com.google.spanner.v1.ExecuteSqlRequest;
 import com.google.spanner.v1.ExecuteSqlRequest.QueryOptions;
 import com.google.spanner.v1.SpannerGrpc;
+import com.google.spanner.v1.TransactionOptions;
+import com.google.spanner.v1.TransactionOptions.IsolationLevel;
 import io.grpc.CallCredentials;
 import io.grpc.CompressorRegistry;
 import io.grpc.Context;
@@ -178,6 +180,7 @@ public class SpannerOptions extends ServiceOptions<Spanner, SpannerOptions> {
   private final boolean enableExtendedTracing;
   private final boolean enableEndToEndTracing;
   private final String monitoringHost;
+  private final TransactionOptions defaultTransactionOptions;
 
   enum TracingFramework {
     OPEN_CENSUS,
@@ -807,6 +810,7 @@ protected SpannerOptions(Builder builder) {
     enableBuiltInMetrics = builder.enableBuiltInMetrics;
     enableEndToEndTracing = builder.enableEndToEndTracing;
     monitoringHost = builder.monitoringHost;
+    defaultTransactionOptions = builder.defaultTransactionOptions;
   }
 
   /**
@@ -988,6 +992,7 @@ public static class Builder
     private String monitoringHost = SpannerOptions.environment.getMonitoringHost();
     private SslContext mTLSContext = null;
     private boolean isExperimentalHost = false;
+    private TransactionOptions defaultTransactionOptions = TransactionOptions.getDefaultInstance();
 
     private static String createCustomClientLibToken(String token) {
       return token + " " + ServiceOptions.getGoogApiClientLibName();
@@ -1056,6 +1061,7 @@ protected Builder() {
       this.enableBuiltInMetrics = options.enableBuiltInMetrics;
       this.enableEndToEndTracing = options.enableEndToEndTracing;
       this.monitoringHost = options.monitoringHost;
+      this.defaultTransactionOptions = options.defaultTransactionOptions;
     }
 
     @Override
@@ -1645,6 +1651,55 @@ public Builder setEnableEndToEndTracing(boolean enableEndToEndTracing) {
       return this;
     }
 
+    /**
+     * Provides the default read-write transaction options for all databases. These defaults are
+     * overridden by any explicit {@link com.google.cloud.spanner.Options.TransactionOption}
+     * provided through {@link DatabaseClient}.
+     *
+     * <p>Example Usage:
+     *
+     * <pre>{@code
+     * DefaultReadWriteTransactionOptions options = DefaultReadWriteTransactionOptions.newBuilder()
+     * .setIsolationLevel(IsolationLevel.SERIALIZABLE)
+     * .build();
+     * }</pre>
+     */
+    public static class DefaultReadWriteTransactionOptions {
+      private final TransactionOptions defaultTransactionOptions;
+
+      private DefaultReadWriteTransactionOptions(TransactionOptions defaultTransactionOptions) {
+        this.defaultTransactionOptions = defaultTransactionOptions;
+      }
+
+      public static DefaultReadWriteTransactionOptionsBuilder newBuilder() {
+        return new DefaultReadWriteTransactionOptionsBuilder();
+      }
+
+      public static class DefaultReadWriteTransactionOptionsBuilder {
+        private final TransactionOptions.Builder transactionOptionsBuilder =
+            TransactionOptions.newBuilder();
+
+        public DefaultReadWriteTransactionOptionsBuilder setIsolationLevel(
+            IsolationLevel isolationLevel) {
+          transactionOptionsBuilder.setIsolationLevel(isolationLevel);
+          return this;
+        }
+
+        public DefaultReadWriteTransactionOptions build() {
+          return new DefaultReadWriteTransactionOptions(transactionOptionsBuilder.build());
+        }
+      }
+    }
+
+    /** Sets the {@link DefaultReadWriteTransactionOptions} for read-write transactions. */
+    public Builder setDefaultTransactionOptions(
+        DefaultReadWriteTransactionOptions defaultReadWriteTransactionOptions) {
+      Preconditions.checkNotNull(
+          defaultReadWriteTransactionOptions, "DefaultReadWriteTransactionOptions cannot be null");
+      this.defaultTransactionOptions = defaultReadWriteTransactionOptions.defaultTransactionOptions;
+      return this;
+    }
+
     @SuppressWarnings("rawtypes")
     @Override
     public SpannerOptions build() {
@@ -1990,6 +2045,10 @@ String getMonitoringHost() {
     return monitoringHost;
   }
 
+  public TransactionOptions getDefaultTransactionOptions() {
+    return defaultTransactionOptions;
+  }
+
   @BetaApi
   public boolean isUseVirtualThreads() {
     return useVirtualThreads;

google-cloud-spanner/src/main/java/com/google/cloud/spanner/TransactionRunnerImpl.java

@@ -643,8 +643,12 @@ TransactionSelector getTransactionSelector() {
           if (tx == null) {
             return TransactionSelector.newBuilder()
                 .setBegin(
-                    SessionImpl.createReadWriteTransactionOptions(
-                        options, getPreviousTransactionId()))
+                    this.session
+                        .defaultTransactionOptions()
+                        .toBuilder()
+                        .mergeFrom(
+                            SessionImpl.createReadWriteTransactionOptions(
+                                options, getPreviousTransactionId())))
                 .build();
           } else {
             // Wait for the transaction to come available. The tx.get() call will fail with an