docs(samples): add load avro table with truncate from gcs (#567)

samples/snippets/src/main/java/com/example/bigquery/LoadAvroFromGCSTruncate.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_load_table_gcs_avro_truncate]
+import com.google.cloud.bigquery.BigQuery;
+import com.google.cloud.bigquery.BigQueryException;
+import com.google.cloud.bigquery.BigQueryOptions;
+import com.google.cloud.bigquery.FormatOptions;
+import com.google.cloud.bigquery.Job;
+import com.google.cloud.bigquery.JobInfo;
+import com.google.cloud.bigquery.LoadJobConfiguration;
+import com.google.cloud.bigquery.TableId;
+
+// Sample to overwrite the BigQuery table data by loading a AVRO file from GCS
+public class LoadAvroFromGCSTruncate {
+
+  public static void runLoadAvroFromGCSTruncate() {
+    // TODO(developer): Replace these variables before running the sample.
+    String datasetName = "MY_DATASET_NAME";
+    String tableName = "MY_TABLE_NAME";
+    String sourceUri = "gs://cloud-samples-data/bigquery/us-states/us-states.avro";
+    loadAvroFromGCSTruncate(datasetName, tableName, sourceUri);
+  }
+
+  public static void loadAvroFromGCSTruncate(
+      String datasetName, String tableName, String sourceUri) {
+    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();
+
+      TableId tableId = TableId.of(datasetName, tableName);
+      LoadJobConfiguration loadConfig =
+          LoadJobConfiguration.newBuilder(tableId, sourceUri)
+              .setFormatOptions(FormatOptions.avro())
+              // Set the write disposition to overwrite existing table data
+              .setWriteDisposition(JobInfo.WriteDisposition.WRITE_TRUNCATE)
+              .build();
+
+      // Load data from a GCS Avro file into the table
+      Job job = bigquery.create(JobInfo.of(loadConfig));
+      // Blocks until this load table job completes its execution, either failing or succeeding.
+      job = job.waitFor();
+      if (job.isDone()) {
+        System.out.println("Table is successfully overwritten by AVRO file loaded from GCS");
+      } else {
+        System.out.println(
+            "BigQuery was unable to load into the table due to an error:"
+                + job.getStatus().getError());
+      }
+    } catch (BigQueryException | InterruptedException e) {
+      System.out.println("Column not added during load append \n" + e.toString());
+    }
+  }
+}
+// [END bigquery_load_table_gcs_avro_truncate]

samples/snippets/src/test/java/com/example/bigquery/LoadAvroFromGCSTruncateIT.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 static junit.framework.TestCase.assertNotNull;
+
+import com.google.cloud.bigquery.Schema;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.UUID;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class LoadAvroFromGCSTruncateIT {
+
+  private String tableName;
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+
+  private static final String BIGQUERY_DATASET_NAME = requireEnvVar("BIGQUERY_DATASET_NAME");
+
+  private static String requireEnvVar(String varName) {
+    String value = System.getenv(varName);
+    assertNotNull(
+        "Environment variable " + varName + " is required to perform these tests.",
+        System.getenv(varName));
+    return value;
+  }
+
+  @BeforeClass
+  public static void checkRequirements() {
+    requireEnvVar("BIGQUERY_DATASET_NAME");
+  }
+
+  @Before
+  public void setUp() {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+
+    // Create a test table
+    tableName = "MY_LOAD_AVRO_TABLE_FROM_GCS_TEST_" + UUID.randomUUID().toString().substring(0, 8);
+    CreateTable.createTable(BIGQUERY_DATASET_NAME, tableName, Schema.of());
+
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+  }
+
+  @After
+  public void tearDown() {
+    // Clean up
+    DeleteTable.deleteTable(BIGQUERY_DATASET_NAME, tableName);
+    System.setOut(null);
+  }
+
+  @Test
+  public void loadLoadAvroFromGCSTruncate() {
+    String sourceUri = "gs://cloud-samples-data/bigquery/us-states/us-states.avro";
+    LoadAvroFromGCSTruncate.loadAvroFromGCSTruncate(BIGQUERY_DATASET_NAME, tableName, sourceUri);
+    assertThat(bout.toString())
+        .contains("Table is successfully overwritten by AVRO file loaded from GCS");
+  }
+}