Getting started with Spanner in Java

Objectives

This tutorial walks you through the following steps using the Spannerclient library for Java:

  • Create a Spanner instance and database.
  • Write, read, and execute SQL queries on data in the database.
  • Update the database schema.
  • Update data using a read-write transaction.
  • Add a secondary index to the database.
  • Use the index to read and execute SQL queries on data.
  • Retrieve data using a read-only transaction.

Costs

This tutorial uses Spanner, which is a billable component of theGoogle Cloud. For information on the cost of using Spanner, seePricing.

Before you begin

Complete the steps described inSet up, which cover creating andsetting a default Google Cloud project, enabling billing, enabling theCloud Spanner API, and setting up OAuth 2.0 to get authentication credentials to usethe Cloud Spanner API.

In particular, make sure that you rungcloud authapplication-default loginto set up your local development environment with authenticationcredentials.

Note: If you don't plan to keep the resources that you create in this tutorial,consider creating a new Google Cloud project instead of selecting an existingproject. After you finish the tutorial, you can delete the project, removing allresources associated with the project.

Prepare your local Java environment

  1. Install the following on your development machine if they are not already installed:

  2. Clone the sample app repository to your local machine:

    gitclonehttps://github.com/googleapis/java-spanner.git

  3. Change to the directory that contains the Spanner sample code:

    cdjava-spanner/samples/snippets

  4. Generate the sample JAR file:

    mvncleanpackage

Create an instance

When you first use Spanner, you must create an instance, which is anallocation of resources that are used by Spanner databases. When youcreate an instance, you choose aninstance configuration, which determineswhere your data is stored, and also the number of nodes to use, which determinesthe amount of serving and storage resources in your instance.

SeeCreate an instanceto learn how to create a Spanner instance using any of thefollowing methods. You can name your instancetest-instance to use it withother topics in this document that reference an instance namedtest-instance.

  • The Google Cloud CLI
  • The Google Cloud console
  • A client library (C++, C#, Go, Java, Node.js, PHP, Python, or Ruby)

Look through sample files

The samples repository contains a sample that shows how to use Spannerwith Java.

Create a database

GoogleSQL

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\createdatabasetest-instanceexample-db

PostgreSQL

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\createpgdatabasetest-instanceexample-db

You should see:

Createddatabase[example-db]
The following code creates a database and two tables in the database.Note: The subsequent code samples use these two tables. If you don't executethis code, then create the tables by using the Google Cloud console or thegcloud CLI. For more information, see theexample schema.

GoogleSQL

staticvoidcreateDatabase(DatabaseAdminClientdbAdminClient,InstanceNameinstanceName,StringdatabaseId){CreateDatabaseRequestcreateDatabaseRequest=CreateDatabaseRequest.newBuilder().setCreateStatement("CREATE DATABASE `"+databaseId+"`").setParent(instanceName.toString()).addAllExtraStatements(Arrays.asList("CREATE TABLE Singers ("+"  SingerId   INT64 NOT NULL,"+"  FirstName  STRING(1024),"+"  LastName   STRING(1024),"+"  SingerInfo BYTES(MAX),"+"  FullName STRING(2048) AS "+"  (ARRAY_TO_STRING([FirstName, LastName], \" \")) STORED"+") PRIMARY KEY (SingerId)","CREATE TABLE Albums ("+"  SingerId     INT64 NOT NULL,"+"  AlbumId      INT64 NOT NULL,"+"  AlbumTitle   STRING(MAX)"+") PRIMARY KEY (SingerId, AlbumId),"+"  INTERLEAVE IN PARENT Singers ON DELETE CASCADE")).build();try{// Initiate the request which returns an OperationFuture.com.google.spanner.admin.database.v1.Databasedb=dbAdminClient.createDatabaseAsync(createDatabaseRequest).get();System.out.println("Created database ["+db.getName()+"]");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

PostgreSQL

staticvoidcreatePostgreSqlDatabase(DatabaseAdminClientdbAdminClient,StringprojectId,StringinstanceId,StringdatabaseId){finalCreateDatabaseRequestrequest=CreateDatabaseRequest.newBuilder().setCreateStatement("CREATE DATABASE \""+databaseId+"\"").setParent(InstanceName.of(projectId,instanceId).toString()).setDatabaseDialect(DatabaseDialect.POSTGRESQL).build();try{// Initiate the request which returns an OperationFuture.Databasedb=dbAdminClient.createDatabaseAsync(request).get();System.out.println("Created database ["+db.getName()+"]");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}staticvoidcreateTableUsingDdl(DatabaseAdminClientdbAdminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.dbAdminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("CREATE TABLE Singers ("+"  SingerId   bigint NOT NULL,"+"  FirstName  character varying(1024),"+"  LastName   character varying(1024),"+"  SingerInfo bytea,"+"  FullName character varying(2048) GENERATED "+"  ALWAYS AS (FirstName || ' ' || LastName) STORED,"+"  PRIMARY KEY (SingerId)"+")","CREATE TABLE Albums ("+"  SingerId     bigint NOT NULL,"+"  AlbumId      bigint NOT NULL,"+"  AlbumTitle   character varying(1024),"+"  PRIMARY KEY (SingerId, AlbumId)"+") INTERLEAVE IN PARENT Singers ON DELETE CASCADE")).get();System.out.println("Created Singers & Albums tables in database: ["+databaseName+"]");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throwSpannerExceptionFactory.asSpannerException(e);}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

The next step is to write data to your database.

Create a database client

Before you can do reads or writes, you must create aDatabaseClient.You can think of aDatabaseClient as a database connection: all of yourinteractions with Spanner must go through aDatabaseClient. Typicallyyou create aDatabaseClient when your application starts up, then you re-usethatDatabaseClient to read, write, and execute transactions.

SpannerOptionsoptions=SpannerOptions.newBuilder().build();Spannerspanner=options.getService();DatabaseAdminClientdbAdminClient=null;try{DatabaseClientdbClient=spanner.getDatabaseClient(db);dbAdminClient=spanner.createDatabaseAdminClient();}finally{if(dbAdminClient!=null){if(!dbAdminClient.isShutdown()||!dbAdminClient.isTerminated()){dbAdminClient.close();}}spanner.close();}

Each client uses resources in Spanner, so it is good practice to closeunneeded clients by callingclose().

Read more in theDatabaseClientJavadoc reference.

Write data with DML

You can insert data using Data Manipulation Language (DML) in a read-writetransaction.

You use theexecuteUpdate() method to execute a DML statement.

staticvoidwriteUsingDml(DatabaseClientdbClient){// Insert 4 singer recordsdbClient.readWriteTransaction().run(transaction->{Stringsql="INSERT INTO Singers (SingerId, FirstName, LastName) VALUES "+"(12, 'Melissa', 'Garcia'), "+"(13, 'Russell', 'Morales'), "+"(14, 'Jacqueline', 'Long'), "+"(15, 'Dylan', 'Shaw')";longrowCount=transaction.executeUpdate(Statement.of(sql));System.out.printf("%d records inserted.\n",rowCount);returnnull;});}

Run the sample using thewriteusingdml argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\writeusingdmltest-instanceexample-db

You should see:

4recordsinserted.
Note: There are limits to commit size. SeeCRUD limitfor more information.

Write data with mutations

You can also insert data usingmutations.

You can write data usingaMutation object.AMutation object is a container for mutation operations. AMutationrepresents a sequence of inserts, updates, and deletes that Spannerapplies atomically to different rows and tables in a Spanner database.

ThenewInsertBuilder()method in theMutation class constructs anINSERT mutation, which inserts anew row in a table. If the row already exists, the write fails. Alternatively,you can use thenewInsertOrUpdateBuildermethod to construct anINSERT_OR_UPDATE mutation, which updates column valuesif the row already exists.

Thewrite()method in theDatabaseClient class writes the mutations. All mutations in asingle batch are applied atomically.

This code shows how to write the data using mutations:

staticfinalList<Singer>SINGERS=Arrays.asList(newSinger(1,"Marc","Richards"),newSinger(2,"Catalina","Smith"),newSinger(3,"Alice","Trentor"),newSinger(4,"Lea","Martin"),newSinger(5,"David","Lomond"));staticfinalList<Album>ALBUMS=Arrays.asList(newAlbum(1,1,"Total Junk"),newAlbum(1,2,"Go, Go, Go"),newAlbum(2,1,"Green"),newAlbum(2,2,"Forever Hold Your Peace"),newAlbum(2,3,"Terrified"));staticvoidwriteExampleData(DatabaseClientdbClient){List<Mutation>mutations=newArrayList<>();for(Singersinger:SINGERS){mutations.add(Mutation.newInsertBuilder("Singers").set("SingerId").to(singer.singerId).set("FirstName").to(singer.firstName).set("LastName").to(singer.lastName).build());}for(Albumalbum:ALBUMS){mutations.add(Mutation.newInsertBuilder("Albums").set("SingerId").to(album.singerId).set("AlbumId").to(album.albumId).set("AlbumTitle").to(album.albumTitle).build());}dbClient.write(mutations);}

Run the sample using thewrite argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\writetest-instanceexample-db

You should see the command run successfully.

Note: There are limits to commit size. SeeCRUD limitfor more information.

Query data using SQL

Spanner supports a SQL interface for reading data, which you canaccess on the command line using the Google Cloud CLI orprogrammatically usingthe Spanner client library for Java.

On the command line

Execute the following SQL statement to read the values of all columns from theAlbums table:

gcloudspannerdatabasesexecute-sqlexample-db--instance=test-instance\--sql='SELECTSingerId,AlbumId,AlbumTitleFROMAlbums'
Note: For the GoogleSQL reference, seeQuery syntax in GoogleSQLand for PostgreSQL reference, seePostgreSQL lexical structure and syntax.

The result shows:

SingerIdAlbumIdAlbumTitle11TotalJunk12Go,Go,Go21Green22ForeverHoldYourPeace23Terrified

Use the Spanner client library for Java

In addition to executing a SQL statement on the command line, you can issue thesame SQL statement programmatically using the Spanner client library forJava.

The following methods and classes are used to run the SQL query:

  • ThesingleUse()method in theDatabaseClient class: use this to read the value of one or morecolumns from one or more rows in a Spanner table.singleUse() returnsaReadContext object, which is used for running a read or SQL statement.
  • TheexecuteQuery()method of theReadContext class: use this method to execute a query againsta database.
  • TheStatementclass: use this to construct a SQL string.
  • TheResultSetclass: use this to access the data returned by a SQL statement or read call.

Here's how to issue the query and access the data:

staticvoidquery(DatabaseClientdbClient){try(ResultSetresultSet=dbClient.singleUse()// Execute a single read or query against Cloud Spanner..executeQuery(Statement.of("SELECT SingerId, AlbumId, AlbumTitle FROM Albums"))){while(resultSet.next()){System.out.printf("%d %d %s\n",resultSet.getLong(0),resultSet.getLong(1),resultSet.getString(2));}}}

Run the sample using thequery argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\querytest-instanceexample-db

You should see the following result:

11TotalJunk12Go,Go,Go21Green22ForeverHoldYourPeace23Terrified

Query using a SQL parameter

If your application has a frequently executed query, you can improve its performanceby parameterizing it. The resulting parametric query can be cached and reused, whichreduces compilation costs. For more information, seeUse query parameters to speed up frequently executed queries.

Here is an example of using a parameter in theWHERE clause toquery records containing a specific value forLastName.

GoogleSQL

staticvoidqueryWithParameter(DatabaseClientdbClient){Statementstatement=Statement.newBuilder("SELECT SingerId, FirstName, LastName "+"FROM Singers "+"WHERE LastName = @lastName").bind("lastName").to("Garcia").build();try(ResultSetresultSet=dbClient.singleUse().executeQuery(statement)){while(resultSet.next()){System.out.printf("%d %s %s\n",resultSet.getLong("SingerId"),resultSet.getString("FirstName"),resultSet.getString("LastName"));}}}

PostgreSQL

staticvoidqueryWithParameter(DatabaseClientdbClient){Statementstatement=Statement.newBuilder("SELECT singerid AS \"SingerId\", "+"firstname as \"FirstName\", lastname as \"LastName\" "+"FROM Singers "+"WHERE LastName = $1").bind("p1").to("Garcia").build();try(ResultSetresultSet=dbClient.singleUse().executeQuery(statement)){while(resultSet.next()){System.out.printf("%d %s %s\n",resultSet.getLong("SingerId"),resultSet.getString("FirstName"),resultSet.getString("LastName"));}}}

Run the sample using the queryWithParameter argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\querywithparametertest-instanceexample-db

You should see the following result:

12MelissaGarcia

Read data using the read API

In addition to Spanner's SQL interface, Spanner also supports aread interface.

Use theread()method of theReadContext class to read rows from the database. Use aKeySetobject to define a collection of keys and key ranges to read.

Here's how to read the data:

staticvoidread(DatabaseClientdbClient){try(ResultSetresultSet=dbClient.singleUse().read("Albums",KeySet.all(),// Read all rows in a table.Arrays.asList("SingerId","AlbumId","AlbumTitle"))){while(resultSet.next()){System.out.printf("%d %d %s\n",resultSet.getLong(0),resultSet.getLong(1),resultSet.getString(2));}}}

Run the sample using theread argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\readtest-instanceexample-db

You should see output similar to:

11TotalJunk12Go,Go,Go21Green22ForeverHoldYourPeace23Terrified

Update the database schema

Assume you need to add a new column calledMarketingBudget to theAlbumstable. Adding a new column to an existing table requires an update to yourdatabase schema. Spanner supports schema updates to a database while thedatabase continues to serve traffic. Schema updates don't require taking thedatabase offline and they don't lock entire tables or columns; you can continuewriting data to the database during the schema update. Read more about supportedschema updates and schema change performance inMake schema updates.

Add a column

You can add a column on the command line using the Google Cloud CLI orprogrammatically usingthe Spanner client library for Java.

On the command line

Use the followingALTER TABLE command toadd the new column to the table:

GoogleSQL

gcloudspannerdatabasesddlupdateexample-db--instance=test-instance\--ddl='ALTERTABLEAlbumsADDCOLUMNMarketingBudgetINT64'

PostgreSQL

gcloudspannerdatabasesddlupdateexample-db--instance=test-instance\--ddl='ALTERTABLEAlbumsADDCOLUMNMarketingBudgetBIGINT'

You should see:

Schemaupdating...done.

Use the Spanner client library for Java

Use theupdateDatabaseDdl()method of theDatabaseAdminClient class to modify the schema:

GoogleSQL

staticvoidaddMarketingBudget(DatabaseAdminClientadminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.adminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("ALTER TABLE Albums ADD COLUMN MarketingBudget INT64")).get();System.out.println("Added MarketingBudget column");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

PostgreSQL

staticvoidaddMarketingBudget(DatabaseAdminClientadminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.adminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("ALTER TABLE Albums ADD COLUMN MarketingBudget bigint")).get();System.out.println("Added MarketingBudget column");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

Run the sample using theaddmarketingbudget argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\addmarketingbudgettest-instanceexample-db

You should see:

AddedMarketingBudgetcolumn.

Write data to the new column

The following code writes data to the new column. It setsMarketingBudget to100000 for the row keyed byAlbums(1, 1) and to500000 for the row keyedbyAlbums(2, 2).

staticvoidupdate(DatabaseClientdbClient){// Mutation can be used to update/insert/delete a single row in a table. Here we use// newUpdateBuilder to create update mutations.List<Mutation>mutations=Arrays.asList(Mutation.newUpdateBuilder("Albums").set("SingerId").to(1).set("AlbumId").to(1).set("MarketingBudget").to(100000).build(),Mutation.newUpdateBuilder("Albums").set("SingerId").to(2).set("AlbumId").to(2).set("MarketingBudget").to(500000).build());// This writes all the mutations to Cloud Spanner atomically.dbClient.write(mutations);}

Run the sample using theupdate argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\updatetest-instanceexample-db

You can also execute a SQL query or a read call to fetch the values that youjust wrote.

Here's the code to execute the query:

GoogleSQL

staticvoidqueryMarketingBudget(DatabaseClientdbClient){// Rows without an explicit value for MarketingBudget will have a MarketingBudget equal to// null. A try-with-resource block is used to automatically release resources held by// ResultSet.try(ResultSetresultSet=dbClient.singleUse().executeQuery(Statement.of("SELECT SingerId, AlbumId, MarketingBudget FROM Albums"))){while(resultSet.next()){System.out.printf("%d %d %s\n",resultSet.getLong("SingerId"),resultSet.getLong("AlbumId"),// We check that the value is non null. ResultSet getters can only be used to retrieve// non null values.resultSet.isNull("MarketingBudget")?"NULL":resultSet.getLong("MarketingBudget"));}}}

PostgreSQL

staticvoidqueryMarketingBudget(DatabaseClientdbClient){// Rows without an explicit value for MarketingBudget will have a MarketingBudget equal to// null. A try-with-resource block is used to automatically release resources held by// ResultSet.try(ResultSetresultSet=dbClient.singleUse().executeQuery(Statement.of("SELECT singerid as \"SingerId\", "+"albumid as \"AlbumId\", marketingbudget as \"MarketingBudget\" "+"FROM Albums"))){while(resultSet.next()){System.out.printf("%d %d %s\n",resultSet.getLong("SingerId"),resultSet.getLong("AlbumId"),// We check that the value is non null. ResultSet getters can only be used to retrieve// non null values.resultSet.isNull("MarketingBudget")?"NULL":resultSet.getLong("MarketingBudget"));}}}

To execute this query, run the sample using thequerymarketingbudget argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\querymarketingbudgettest-instanceexample-db

You should see:

1110000012NULL21NULL2250000023NULL

Update data

You can update data using DML in a read-write transaction.

You use theexecuteUpdate()method to execute a DML statement.

GoogleSQL

staticvoidwriteWithTransactionUsingDml(DatabaseClientdbClient){dbClient.readWriteTransaction().run(transaction->{// Transfer marketing budget from one album to another. We do it in a transaction to// ensure that the transfer is atomic.Stringsql1="SELECT MarketingBudget from Albums WHERE SingerId = 2 and AlbumId = 2";ResultSetresultSet=transaction.executeQuery(Statement.of(sql1));longalbum2Budget=0;while(resultSet.next()){album2Budget=resultSet.getLong("MarketingBudget");}// Transaction will only be committed if this condition still holds at the time of// commit. Otherwise it will be aborted and the callable will be rerun by the// client library.longtransfer=200000;if(album2Budget>=transfer){Stringsql2="SELECT MarketingBudget from Albums WHERE SingerId = 1 and AlbumId = 1";ResultSetresultSet2=transaction.executeQuery(Statement.of(sql2));longalbum1Budget=0;while(resultSet2.next()){album1Budget=resultSet2.getLong("MarketingBudget");}album1Budget+=transfer;album2Budget-=transfer;StatementupdateStatement=Statement.newBuilder("UPDATE Albums "+"SET MarketingBudget = @AlbumBudget "+"WHERE SingerId = 1 and AlbumId = 1").bind("AlbumBudget").to(album1Budget).build();transaction.executeUpdate(updateStatement);StatementupdateStatement2=Statement.newBuilder("UPDATE Albums "+"SET MarketingBudget = @AlbumBudget "+"WHERE SingerId = 2 and AlbumId = 2").bind("AlbumBudget").to(album2Budget).build();transaction.executeUpdate(updateStatement2);}returnnull;});}

PostgreSQL

staticvoidwriteWithTransactionUsingDml(DatabaseClientdbClient){dbClient.readWriteTransaction().run(transaction->{// Transfer marketing budget from one album to another. We do it in a transaction to// ensure that the transfer is atomic.Stringsql1="SELECT marketingbudget as \"MarketingBudget\" from Albums WHERE "+"SingerId = 2 and AlbumId = 2";ResultSetresultSet=transaction.executeQuery(Statement.of(sql1));longalbum2Budget=0;while(resultSet.next()){album2Budget=resultSet.getLong("MarketingBudget");}// Transaction will only be committed if this condition still holds at the time of// commit. Otherwise it will be aborted and the callable will be rerun by the// client library.longtransfer=200000;if(album2Budget>=transfer){Stringsql2="SELECT marketingbudget as \"MarketingBudget\" from Albums WHERE "+"SingerId = 1 and AlbumId = 1";ResultSetresultSet2=transaction.executeQuery(Statement.of(sql2));longalbum1Budget=0;while(resultSet2.next()){album1Budget=resultSet2.getLong("MarketingBudget");}album1Budget+=transfer;album2Budget-=transfer;StatementupdateStatement=Statement.newBuilder("UPDATE Albums "+"SET MarketingBudget = $1 "+"WHERE SingerId = 1 and AlbumId = 1").bind("p1").to(album1Budget).build();transaction.executeUpdate(updateStatement);StatementupdateStatement2=Statement.newBuilder("UPDATE Albums "+"SET MarketingBudget = $1 "+"WHERE SingerId = 2 and AlbumId = 2").bind("p1").to(album2Budget).build();transaction.executeUpdate(updateStatement2);}returnnull;});}

Run the sample using thewritewithtransactionusingdml argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\writewithtransactionusingdmltest-instanceexample-db
Note: You can alsoupdate data using mutations.

Use a secondary index

Suppose you wanted to fetch all rows ofAlbums that haveAlbumTitle valuesin a certain range. You could read all values from theAlbumTitle column usinga SQL statement or a read call, and then discard the rows that don't meet thecriteria, but doing this full table scan is expensive, especially for tableswith a lot of rows. Instead you can speed up the retrieval of rows whensearching by non-primary key columns by creating asecondary index on the table.

Adding a secondary index to an existing table requires a schema update. Likeother schema updates, Spanner supports adding an index while thedatabase continues to serve traffic. Spanner automatically backfills theindex with your existing data. Backfills might take a few minutes to complete,but you don't need to take the database offline or avoid writing to the indexedtable during this process. For more details, seeAdd a secondary index.

After you add a secondary index, Spanner automatically uses it forSQL queries that are likely to run faster with the index. If you use the readinterface, you must specify the index that you want to use.

Add a secondary index

You can add an index on the command line using the gcloud CLI orprogrammatically using the Spanner client library for Java.

On the command line

Use the followingCREATE INDEX commandto add an index to the database:

gcloudspannerdatabasesddlupdateexample-db--instance=test-instance\--ddl='CREATE INDEX AlbumsByAlbumTitle ON Albums(AlbumTitle)'

You should see:

Schemaupdating...done.

Using the Spanner client library for Java

Use theupdateDatabaseDdl()method of theDatabaseAdminClient class to add an index:

staticvoidaddIndex(DatabaseAdminClientadminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.adminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("CREATE INDEX AlbumsByAlbumTitle ON Albums(AlbumTitle)")).get();System.out.println("Added AlbumsByAlbumTitle index");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

Run the sample using theaddindex argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\addindextest-instanceexample-db

Adding an index can take a few minutes. After the index is added, you shouldsee:

AddedtheAlbumsByAlbumTitleindex.

Read using the index

For SQL queries, Spanner automatically uses an appropriate index. In theread interface, you must specify the index in your request.

To use the index in the read interface, use thereadUsingIndex() method of theReadContext class.

The following code fetches allAlbumId, andAlbumTitlecolumns from theAlbumsByAlbumTitle index.

staticvoidreadUsingIndex(DatabaseClientdbClient){try(ResultSetresultSet=dbClient.singleUse().readUsingIndex("Albums","AlbumsByAlbumTitle",KeySet.all(),Arrays.asList("AlbumId","AlbumTitle"))){while(resultSet.next()){System.out.printf("%d %s\n",resultSet.getLong(0),resultSet.getString(1));}}}

Run the sample using thereadindex argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\readindextest-instanceexample-db

You should see:

2ForeverHoldYourPeace2Go,Go,Go1Green3Terrified1TotalJunk

Add an index for index-only reads

You might have noticed that the previous read example doesn't include readingtheMarketingBudget column. This is because Spanner's read interfacedoesn't support the ability to join an index with a data table to look up valuesthat are not stored in the index.

Create an alternate definition ofAlbumsByAlbumTitle that stores a copy ofMarketingBudget in the index.

On the command line

GoogleSQL

gcloudspannerdatabasesddlupdateexample-db--instance=test-instance\--ddl='CREATEINDEXAlbumsByAlbumTitle2ONAlbums(AlbumTitle)STORING(MarketingBudget)

PostgreSQL

gcloudspannerdatabasesddlupdateexample-db--instance=test-instance\--ddl='CREATEINDEXAlbumsByAlbumTitle2ONAlbums(AlbumTitle)INCLUDE(MarketingBudget)

Adding an index can take a few minutes. After the index is added, you shouldsee:

Schemaupdating...done.

Using the Spanner client library for Java

Use theupdateDatabaseDdl()method of theDatabaseAdminClient class to add an index with aSTORINGclause for GoogleSQL andINCLUDE clause for PostgreSQL:

GoogleSQL

staticvoidaddStoringIndex(DatabaseAdminClientadminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.adminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("CREATE INDEX AlbumsByAlbumTitle2 ON Albums(AlbumTitle) "+"STORING (MarketingBudget)")).get();System.out.println("Added AlbumsByAlbumTitle2 index");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

PostgreSQL

staticvoidaddStoringIndex(DatabaseAdminClientadminClient,DatabaseNamedatabaseName){try{// Initiate the request which returns an OperationFuture.adminClient.updateDatabaseDdlAsync(databaseName,Arrays.asList("CREATE INDEX AlbumsByAlbumTitle2 ON Albums(AlbumTitle) "+"INCLUDE (MarketingBudget)")).get();System.out.println("Added AlbumsByAlbumTitle2 index");}catch(ExecutionExceptione){// If the operation failed during execution, expose the cause.throw(SpannerException)e.getCause();}catch(InterruptedExceptione){// Throw when a thread is waiting, sleeping, or otherwise occupied,// and the thread is interrupted, either before or during the activity.throwSpannerExceptionFactory.propagateInterrupt(e);}}

Run the sample using theaddstoringindex argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\addstoringindextest-instanceexample-db

Adding an index can take a few minutes. After the index is added, you shouldsee:

AddedAlbumsByAlbumTitle2index

Now you can execute a read that fetches allAlbumId,AlbumTitle, andMarketingBudget columns from theAlbumsByAlbumTitle2 index:

staticvoidreadStoringIndex(DatabaseClientdbClient){// We can read MarketingBudget also from the index since it stores a copy of MarketingBudget.try(ResultSetresultSet=dbClient.singleUse().readUsingIndex("Albums","AlbumsByAlbumTitle2",KeySet.all(),Arrays.asList("AlbumId","AlbumTitle","MarketingBudget"))){while(resultSet.next()){System.out.printf("%d %s %s\n",resultSet.getLong(0),resultSet.getString(1),resultSet.isNull("MarketingBudget")?"NULL":resultSet.getLong("MarketingBudget"));}}}

Run the sample using thereadstoringindex argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\readstoringindextest-instanceexample-db

You should see output similar to:

2ForeverHoldYourPeace3000002Go,Go,GoNULL1GreenNULL3TerrifiedNULL1TotalJunk300000

Retrieve data using read-only transactions

Suppose you want to execute more than one read at the same timestamp.Read-onlytransactions observe a consistentprefix of the transaction commit history, so your application always getsconsistent data. Use aReadOnlyTransactionobject for executing read-only transactions. Use thereadOnlyTransaction()method of theDatabaseClient class to get aReadOnlyTransaction object.

The following shows how to run a query and perform a read in the same read-onlytransaction:

staticvoidreadOnlyTransaction(DatabaseClientdbClient){// ReadOnlyTransaction must be closed by calling close() on it to release resources held by it.// We use a try-with-resource block to automatically do so.try(ReadOnlyTransactiontransaction=dbClient.readOnlyTransaction()){try(ResultSetqueryResultSet=transaction.executeQuery(Statement.of("SELECT SingerId, AlbumId, AlbumTitle FROM Albums"))){while(queryResultSet.next()){System.out.printf("%d %d %s\n",queryResultSet.getLong(0),queryResultSet.getLong(1),queryResultSet.getString(2));}}// queryResultSet.close() is automatically called heretry(ResultSetreadResultSet=transaction.read("Albums",KeySet.all(),Arrays.asList("SingerId","AlbumId","AlbumTitle"))){while(readResultSet.next()){System.out.printf("%d %d %s\n",readResultSet.getLong(0),readResultSet.getLong(1),readResultSet.getString(2));}}// readResultSet.close() is automatically called here}// transaction.close() is automatically called here}

Run the sample using thereadonlytransaction argument.

java-jartarget/spanner-snippets/spanner-google-cloud-samples.jar\readonlytransactiontest-instanceexample-db

You should see output similar to:

22ForeverHoldYourPeace12Go,Go,Go21Green23Terrified11TotalJunk11TotalJunk12Go,Go,Go21Green22ForeverHoldYourPeace23Terrified

Cleanup

To avoid incurring additional charges to your Cloud Billing account for theresources used in this tutorial, drop the database and delete the instance thatyou created.

Delete the database

If you delete an instance, all databases within it are automatically deleted.This step shows how to delete a database without deleting an instance (you wouldstill incur charges for the instance).

On the command line

gcloudspannerdatabasesdeleteexample-db--instance=test-instance

Using the Google Cloud console

  1. Go to theSpanner Instances page in the Google Cloud console.

    Go to the Instances page

  2. Click the instance.

  3. Click the database that you want to delete.

  4. In theDatabase details page, clickDelete.

  5. Confirm that you want to delete the database and clickDelete.

Delete the instance

Deleting an instance automatically drops all databases created in that instance.

On the command line

gcloudspannerinstancesdeletetest-instance

Using the Google Cloud console

  1. Go to theSpanner Instances page in the Google Cloud console.

    Go to the Instances page

  2. Click your instance.

  3. ClickDelete.

  4. Confirm that you want to delete the instance and clickDelete.

What's next

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Last updated 2025-12-15 UTC.