Add Spanner BatchQuery sample.

spanner/cloud-client/pom.xml

@@ -128,7 +128,7 @@ limitations under the License.
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-bom</artifactId>
-        <version>0.34.0-alpha</version>
+        <version>0.37.0-alpha</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>

spanner/cloud-client/src/main/java/com/example/spanner/BatchSample.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.spanner;
+
+import com.google.cloud.spanner.BatchClient;
+import com.google.cloud.spanner.BatchReadOnlyTransaction;
+import com.google.cloud.spanner.DatabaseId;
+import com.google.cloud.spanner.Partition;
+import com.google.cloud.spanner.PartitionOptions;
+import com.google.cloud.spanner.ResultSet;
+import com.google.cloud.spanner.Spanner;
+import com.google.cloud.spanner.SpannerOptions;
+import com.google.cloud.spanner.Statement;
+import com.google.cloud.spanner.TimestampBound;
+
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Sample showing how to run a query using the Batch API.
+ */
+public class BatchSample {
+
+  /**
+   * This example showcases how to create a batch client, partition a query, and concurrently read
+   * from multiple partitions.
+   */
+  public static void main(String[] args) throws InterruptedException {
+    if (args.length != 2) {
+      System.err.println("Usage: BatchSample <instance_id> <database_id>");
+      return;
+    }
+
+    /*
+     * CREATE TABLE Singers (
+     *   SingerId   INT64 NOT NULL,
+     *   FirstName  STRING(1024),
+     *   LastName   STRING(1024),
+     *   SingerInfo BYTES(MAX),
+     * ) PRIMARY KEY (SingerId);
+     */
+
+    String instanceId = args[0];
+    String databaseId = args[1];
+
+    SpannerOptions options = SpannerOptions.newBuilder().build();
+    Spanner spanner = options.getService();
+
+    // [START spanner_batch_client]
+    int numThreads = Runtime.getRuntime().availableProcessors();
+    ExecutorService executor = Executors.newFixedThreadPool(numThreads);
+
+    // Statistics
+    int totalPartitions;
+    AtomicInteger totalRecords = new AtomicInteger(0);
+
+    try {
+      BatchClient batchClient = spanner.getBatchClient(
+          DatabaseId.of(options.getProjectId(), instanceId, databaseId));
+
+      final BatchReadOnlyTransaction txn =
+          batchClient.batchReadOnlyTransaction(TimestampBound.strong());
+
+      // A Partition object is serializable and can be used from a different process.
+      List<Partition> partitions = txn.partitionQuery(PartitionOptions.getDefaultInstance(),
+          Statement.of("SELECT SingerId, FirstName, LastName FROM Singers"));
+
+      totalPartitions = partitions.size();
+
+      for (final Partition p : partitions) {
+        executor.execute(() -> {
+          try (ResultSet results = txn.execute(p)) {
+            while (results.next()) {
+              long singerId = results.getLong(0);
+              String firstName = results.getString(1);
+              String lastName = results.getString(2);
+              System.out.println("[" + singerId + "] " + firstName + " " + lastName);
+              totalRecords.getAndIncrement();
+            }
+          }
+        });
+      }
+    } finally {
+      executor.shutdown();
+      executor.awaitTermination(1, TimeUnit.HOURS);
+      spanner.close();
+    }
+
+    double avgRecordsPerPartition = 0.0;
+    if (totalPartitions != 0) {
+      avgRecordsPerPartition = (double) totalRecords.get() / totalPartitions;
+    }
+    System.out.println("totalPartitions=" + totalPartitions);
+    System.out.println("totalRecords=" + totalRecords);
+    System.out.println("avgRecordsPerPartition=" + avgRecordsPerPartition);
+    // [END spanner_batch_client]
+  }
+}