docs(samples): add query dry run (#587)

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

@@ -0,0 +1,59 @@
+/*
+ * 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_dry_run]
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryException;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.Job;
+import com.google.cloud.bigquery.JobInfo;
+import com.google.cloud.bigquery.JobStatistics;
+import com.google.cloud.bigquery.QueryJobConfiguration;
+
+// Sample to run dry query on the table
+public class QueryDryRun {
+
+  public static void runQueryDryRun() {
+    String query =
+        "SELECT name, COUNT(*) as name_count "
+            + "FROM `bigquery-public-data.usa_names.usa_1910_2013` "
+            + "WHERE state = 'WA' "
+            + "GROUP BY name";
+    queryDryRun(query);
+  }
+
+  public static void queryDryRun(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).setDryRun(true).setUseQueryCache(false).build();
+
+      Job job = bigquery.create(JobInfo.of(queryConfig));
+      JobStatistics.QueryStatistics statistics = job.getStatistics();
+
+      System.out.println(
+          "Query dry run performed successfully." + statistics.getTotalBytesProcessed());
+    } catch (BigQueryException e) {
+      System.out.println("Query not performed \n" + e.toString());
+    }
+  }
+}
+// [END bigquery_query_dry_run]

samples/snippets/src/test/java/com/example/bigquery/QueryDryRunIT.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 QueryDryRunIT {
+
+  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 testQueryDryRun() {
+    String query =
+        "SELECT name, COUNT(*) as name_count "
+            + "FROM `bigquery-public-data.usa_names.usa_1910_2013` "
+            + "WHERE state = 'WA' "
+            + "GROUP BY name";
+
+    QueryDryRun.queryDryRun(query);
+    assertThat(bout.toString()).contains("Query dry run performed successfully.");
+  }
+}