samples: Spanner stale read (googleapis#831)

samples/snippets/src/main/java/com/example/spanner/SpannerSample.java

@@ -16,47 +16,29 @@
 
 package com.example.spanner;
 
-// [START transaction_import]
 import static com.google.cloud.spanner.TransactionRunner.TransactionCallable;
-// [END transaction_import]
 
 import com.google.cloud.spanner.Database;
 import com.google.cloud.spanner.DatabaseAdminClient;
 import com.google.cloud.spanner.DatabaseClient;
 import com.google.cloud.spanner.DatabaseId;
-// [START transaction_import]
 import com.google.cloud.spanner.Key;
-// [END transaction_import]
-// [START read_import]
 import com.google.cloud.spanner.KeySet;
-// [END read_import]
-// [START write_import]
 import com.google.cloud.spanner.Mutation;
-// [END write_import]
 import com.google.cloud.spanner.Operation;
-// [START read_only_transaction_import]
 import com.google.cloud.spanner.ReadOnlyTransaction;
-// [END read_only_transaction_import]
-// [START query_import]
 import com.google.cloud.spanner.ResultSet;
-// [END query_import]
 import com.google.cloud.spanner.Spanner;
 import com.google.cloud.spanner.SpannerOptions;
-// [START query_import]
 import com.google.cloud.spanner.Statement;
-// [END query_import]
-// [START transaction_import]
 import com.google.cloud.spanner.Struct;
+import com.google.cloud.spanner.TimestampBound;
 import com.google.cloud.spanner.TransactionContext;
-// [END transaction_import]
 import com.google.spanner.admin.database.v1.CreateDatabaseMetadata;
-
-// [START write_import]
-
 import java.util.ArrayList;
-// [END write_import]
 import java.util.Arrays;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 /**
  * Example code for using the Cloud Spanner API. This example demonstrates all the common
@@ -67,11 +49,14 @@
  * <li> Writing data using a read-write transaction.
  * <li> Using an index to read and execute SQL queries over data.
  * </ul>
- *
  */
 public class SpannerSample {
-  /** Class to contain singer sample data. */
+
+  /**
+   * Class to contain singer sample data.
+   */
   static class Singer {
+
     final long singerId;
     final String firstName;
     final String lastName;
@@ -83,8 +68,11 @@ static class Singer {
     }
   }
 
-  /** Class to contain album sample data. */
+  /**
+   * Class to contain album sample data.
+   */
   static class Album {
+
     final long singerId;
     final long albumId;
     final String albumTitle;
@@ -116,22 +104,22 @@ static class Album {
 
   static void createDatabase(DatabaseAdminClient dbAdminClient, DatabaseId id) {
     Operation<Database, CreateDatabaseMetadata> op = dbAdminClient
-            .createDatabase(
-                id.getInstanceId().getInstance(),
-                id.getDatabase(),
-                Arrays.asList(
-                    "CREATE TABLE Singers (\n"
-                        + "  SingerId   INT64 NOT NULL,\n"
-                        + "  FirstName  STRING(1024),\n"
-                        + "  LastName   STRING(1024),\n"
-                        + "  SingerInfo BYTES(MAX)\n"
-                        + ") PRIMARY KEY (SingerId)",
-                    "CREATE TABLE Albums (\n"
-                        + "  SingerId     INT64 NOT NULL,\n"
-                        + "  AlbumId      INT64 NOT NULL,\n"
-                        + "  AlbumTitle   STRING(MAX)\n"
-                        + ") PRIMARY KEY (SingerId, AlbumId),\n"
-                        + "  INTERLEAVE IN PARENT Singers ON DELETE CASCADE"));
+        .createDatabase(
+            id.getInstanceId().getInstance(),
+            id.getDatabase(),
+            Arrays.asList(
+                "CREATE TABLE Singers (\n"
+                    + "  SingerId   INT64 NOT NULL,\n"
+                    + "  FirstName  STRING(1024),\n"
+                    + "  LastName   STRING(1024),\n"
+                    + "  SingerInfo BYTES(MAX)\n"
+                    + ") PRIMARY KEY (SingerId)",
+                "CREATE TABLE Albums (\n"
+                    + "  SingerId     INT64 NOT NULL,\n"
+                    + "  AlbumId      INT64 NOT NULL,\n"
+                    + "  AlbumTitle   STRING(MAX)\n"
+                    + ") PRIMARY KEY (SingerId, AlbumId),\n"
+                    + "  INTERLEAVE IN PARENT Singers ON DELETE CASCADE"));
     Database db = op.waitFor().getResult();
     System.out.println("Created database [" + db.getId() + "]");
   }
@@ -413,6 +401,22 @@ static void readOnlyTransaction(DatabaseClient dbClient) {
   }
   // [END read_only_transaction]
 
+  // [START read_stale_data]
+  static void readStaleData(DatabaseClient dbClient) {
+    ResultSet resultSet =
+        dbClient
+            .singleUse(TimestampBound.ofExactStaleness(10, TimeUnit.SECONDS))
+            .read("Albums",
+                KeySet.all(),
+                Arrays.asList("SingerId", "AlbumId", "MarketingBudget"));
+    while (resultSet.next()) {
+      System.out.printf(
+          "%d %d %s\n", resultSet.getLong(0), resultSet.getLong(1),
+          resultSet.isNull(2) ? "NULL" : resultSet.getLong("MarketingBudget"));
+    }
+  }
+  // [END read_stale_data]
+
   static void run(DatabaseClient dbClient, DatabaseAdminClient dbAdminClient, String command,
       DatabaseId database) {
     switch (command) {
@@ -458,6 +462,9 @@ static void run(DatabaseClient dbClient, DatabaseAdminClient dbAdminClient, Stri
       case "readonlytransaction":
         readOnlyTransaction(dbClient);
         break;
+      case "readstaledata":
+        readStaleData(dbClient);
+        break;
       default:
         printUsageAndExit();
     }

samples/snippets/src/test/java/com/example/spanner/QuickstartSampleIT.java

@@ -18,15 +18,14 @@
 
 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;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-import java.io.ByteArrayOutputStream;
-import java.io.PrintStream;
-
 /**
  * Tests for quickstart sample.
  */

samples/snippets/src/test/java/com/example/spanner/SpannerSampleIT.java

@@ -23,15 +23,14 @@
 import com.google.cloud.spanner.Spanner;
 import com.google.cloud.spanner.SpannerOptions;
 
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-import java.io.ByteArrayOutputStream;
-import java.io.PrintStream;
-
 /**
  * Unit tests for {@code SpannerSample}
  */
@@ -43,6 +42,7 @@ public class SpannerSampleIT {
   private final String databaseId = System.getProperty("spanner.sample.database");
   DatabaseId dbId;
   DatabaseAdminClient dbClient;
+  private long lastUpdateDataTimeInMillis;
 
   private String runSample(String command) throws Exception {
     PrintStream stdOut = System.out;
@@ -83,12 +83,17 @@ public void testSample() throws Exception {
 
     out = runSample("query");
     assertThat(out).contains("1 1 Total Junk");
-
     runSample("addmarketingbudget");
+
+    // wait for 10 seconds to elapse and then run an update, and query for stale data
+    lastUpdateDataTimeInMillis = System.currentTimeMillis();
+    while (System.currentTimeMillis() < lastUpdateDataTimeInMillis + 11000) {
+      Thread.sleep(1000);
+    }
     runSample("update");
-
+    out = runSample("readstaledata");
+    assertThat(out).contains("1 1 NULL");
     runSample("writetransaction");
-
     out = runSample("querymarketingbudget");
     assertThat(out).contains("1 1 300000");
     assertThat(out).contains("2 2 300000");