docs(samples): add query batch (#469)

Author: Praful Makani

samples/snippets/src/main/java/com/example/bigquery/QueryBatch.java

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+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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.bigquery;
+
+// [START bigquery_query_batch]
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryException;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.QueryJobConfiguration;
+import com.google.cloud.bigquery.TableResult;
+
+// Sample to query batch in a table
+public class QueryBatch {
+
+  public static void runQueryBatch() {
+    // TODO(developer): Replace these variables before running the sample.
+    String projectId = "MY_PROJECT_ID";
+    String datasetName = "MY_DATASET_NAME";
+    String tableName = "MY_TABLE_NAME";
+    String query =
+        "SELECT corpus"
+            + " FROM `"
+            + projectId
+            + "."
+            + datasetName
+            + "."
+            + tableName
+            + " GROUP BY corpus;";
+    queryBatch(query);
+  }
+
+  public static void queryBatch(String query) {
+    try {
+      // Initialize client that will be used to send requests. This client only needs to be created
+      // once, and can be reused for multiple requests.
+      BigQuery bigquery = BigQueryOptions.getDefaultInstance().getService();
+
+      QueryJobConfiguration queryConfig =
+          QueryJobConfiguration.newBuilder(query)
+              // Run at batch priority, which won't count toward concurrent rate limit.
+              .setPriority(QueryJobConfiguration.Priority.BATCH)
+              .build();
+
+      TableResult results = bigquery.query(queryConfig);
+
+      results
+          .iterateAll()
+          .forEach(row -> row.forEach(val -> System.out.printf("%s,", val.toString())));
+
+      System.out.println("Query batch performed successfully.");
+    } catch (BigQueryException | InterruptedException e) {
+      System.out.println("Query batch not performed \n" + e.toString());
+    }
+  }
+}
+// [END bigquery_query_batch]

samples/snippets/src/test/java/com/example/bigquery/QueryBatchIT.java

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+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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.bigquery;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class QueryBatchIT {
+
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+
+  @Before
+  public void setUp() {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+  }
+
+  @After
+  public void tearDown() {
+    System.setOut(null);
+  }
+
+  @Test
+  public void testQueryBatch() {
+    String query = "SELECT corpus FROM `bigquery-public-data.samples.shakespeare` GROUP BY corpus";
+
+    QueryBatch.queryBatch(query);
+    assertThat(bout.toString()).contains("Query batch performed successfully.");
+  }
+}