docs(samples): add query on external temp table from gcs (#593)

samples/snippets/src/main/java/com/example/bigquery/QueryExternalGCSTemp.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_external_gcs_temp]
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryException;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.CsvOptions;
+import com.google.cloud.bigquery.ExternalTableDefinition;
+import com.google.cloud.bigquery.Field;
+import com.google.cloud.bigquery.QueryJobConfiguration;
+import com.google.cloud.bigquery.Schema;
+import com.google.cloud.bigquery.StandardSQLTypeName;
+import com.google.cloud.bigquery.TableResult;
+
+// Sample to queries an external data source using a temporary table
+public class QueryExternalGCSTemp {
+
+  public static void runQueryExternalGCSTemp() {
+    // TODO(developer): Replace these variables before running the sample.
+    String tableName = "MY_TABLE_NAME";
+    String sourceUri = "gs://cloud-samples-data/bigquery/us-states/us-states.csv";
+    Schema schema =
+        Schema.of(
+            Field.of("name", StandardSQLTypeName.STRING),
+            Field.of("post_abbr", StandardSQLTypeName.STRING));
+    String query = String.format("SELECT * FROM %s WHERE name LIKE 'W%%'", tableName);
+    queryExternalGCSTemp(tableName, sourceUri, schema, query);
+  }
+
+  public static void queryExternalGCSTemp(
+      String tableName, String sourceUri, Schema schema, 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();
+
+      // Skip header row in the file.
+      CsvOptions csvOptions = CsvOptions.newBuilder().setSkipLeadingRows(1).build();
+
+      // Configure the external data source and query job.
+      ExternalTableDefinition externalTable =
+          ExternalTableDefinition.newBuilder(sourceUri, csvOptions).setSchema(schema).build();
+      QueryJobConfiguration queryConfig =
+          QueryJobConfiguration.newBuilder(query)
+              .addTableDefinition(tableName, externalTable)
+              .build();
+
+      // Example query to find states starting with 'W'
+      TableResult results = bigquery.query(queryConfig);
+
+      results
+          .iterateAll()
+          .forEach(row -> row.forEach(val -> System.out.printf("%s,", val.toString())));
+
+      System.out.println("Query on external temporary table performed successfully.");
+    } catch (BigQueryException | InterruptedException e) {
+      System.out.println("Query not performed \n" + e.toString());
+    }
+  }
+}
+// [END bigquery_query_external_gcs_temp]

samples/snippets/src/test/java/com/example/bigquery/QueryExternalGCSTempIT.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 com.google.cloud.bigquery.Field;
+import com.google.cloud.bigquery.Schema;
+import com.google.cloud.bigquery.StandardSQLTypeName;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.UUID;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class QueryExternalGCSTempIT {
+
+  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 testQueryExternalGCSTemp() {
+    String tableName =
+        "EXTERNAL_CSV_TEMP_TABLE_FROM_GCS_TEST_" + UUID.randomUUID().toString().substring(0, 8);
+    String sourceUri = "gs://cloud-samples-data/bigquery/us-states/us-states.csv";
+    Schema schema =
+        Schema.of(
+            Field.of("name", StandardSQLTypeName.STRING),
+            Field.of("post_abbr", StandardSQLTypeName.STRING));
+    String query = String.format("SELECT * FROM %s WHERE name LIKE 'W%%'", tableName);
+    QueryExternalGCSTemp.queryExternalGCSTemp(tableName, sourceUri, schema, query);
+    assertThat(bout.toString())
+        .contains("Query on external temporary table performed successfully.");
+  }
+}