Class BigQueryReadClient (3.4.0)

Service Description: BigQuery Read API.

The Read API can be used to read data from BigQuery.

This class provides the ability to make remote calls to the backing service through method calls that map to API methods. Sample code to get started:

 
 try (BigQueryReadClient BigQueryReadClient = BigQueryReadClient.create()) {
   String parent = "";
   ReadSession readSession = ReadSession.newBuilder().build();
   int maxStreamCount = 0;
   ReadSession response = BigQueryReadClient.createReadSession(parent, readSession, maxStreamCount);
 }
 
 

Note: close() needs to be called on the BigQueryReadClient object to clean up resources such as threads. In the example above, try-with-resources is used, which automatically calls close().

The surface of this class includes several types of Java methods for each of the API's methods:

1. A "flattened" method. With this type of method, the fields of the request type have been converted into function parameters. It may be the case that not all fields are available as parameters, and not every API method will have a flattened method entry point.
2. A "request object" method. This type of method only takes one parameter, a request object, which must be constructed before the call. Not every API method will have a request object method.
3. A "callable" method. This type of method takes no parameters and returns an immutable API callable object, which can be used to initiate calls to the service.

See the individual methods for example code.

Many parameters require resource names to be formatted in a particular way. To assist with these names, this class includes a format method for each type of name, and additionally a parse method to extract the individual identifiers contained within names that are returned.

This class can be customized by passing in a custom instance of BigQueryReadSettings to create(). For example:

To customize credentials:

 
 BigQueryReadSettings BigQueryReadSettings =
     BigQueryReadSettings.newBuilder()
         .setCredentialsProvider(FixedCredentialsProvider.create(myCredentials))
         .build();
 BigQueryReadClient BigQueryReadClient =
     BigQueryReadClient.create(BigQueryReadSettings);
 
 

To customize the endpoint:

 
 BigQueryReadSettings BigQueryReadSettings =
     BigQueryReadSettings.newBuilder().setEndpoint(myEndpoint).build();
 BigQueryReadClient BigQueryReadClient =
     BigQueryReadClient.create(BigQueryReadSettings);
 
 

Constructs an instance of BigQueryReadClient with default settings.

Constructs an instance of BigQueryReadClient, using the given settings. The channels are created based on the settings passed in, or defaults for any settings that are not set.

Constructs an instance of BigQueryReadClient, using the given stub for making calls. This is for advanced usage - prefer to use BigQueryReadSettings}.

Constructs an instance of BigQueryReadClient, using the given settings. This is protected so that it is easy to make a subclass, but otherwise, the static factory methods should be preferred.

Creates a new read session. A read session divides the contents of a BigQuery table into one or more streams, which can then be used to read data from the table. The read session also specifies properties of the data to be read, such as a list of columns or a push-down filter describing the rows to be returned.

A particular row can be read by at most one stream. When the caller has reached the end of each stream in the session, then all the data in the table has been read.

Data is assigned to each stream such that roughly the same number of rows can be read from each stream. Because the server-side unit for assigning data is collections of rows, the API does not guarantee that each stream will return the same number or rows. Additionally, the limits are enforced based on the number of pre-filtered rows, so some filters can lead to lopsided assignments.

Read sessions automatically expire 24 hours after they are created and do not require manual clean-up by the caller.

Sample code:

 try (BigQueryReadClient BigQueryReadClient = BigQueryReadClient.create()) {
   CreateReadSessionRequest request = CreateReadSessionRequest.newBuilder().build();
   ReadSession response = BigQueryReadClient.createReadSession(request);
 }
 

Creates a new read session. A read session divides the contents of a BigQuery table into one or more streams, which can then be used to read data from the table. The read session also specifies properties of the data to be read, such as a list of columns or a push-down filter describing the rows to be returned.

A particular row can be read by at most one stream. When the caller has reached the end of each stream in the session, then all the data in the table has been read.

Data is assigned to each stream such that roughly the same number of rows can be read from each stream. Because the server-side unit for assigning data is collections of rows, the API does not guarantee that each stream will return the same number or rows. Additionally, the limits are enforced based on the number of pre-filtered rows, so some filters can lead to lopsided assignments.

Read sessions automatically expire 24 hours after they are created and do not require manual clean-up by the caller.

Sample code:

 try (BigQueryReadClient BigQueryReadClient = BigQueryReadClient.create()) {
   String parent = "";
   ReadSession readSession = ReadSession.newBuilder().build();
   int maxStreamCount = 0;
   ReadSession response = BigQueryReadClient.createReadSession(parent, readSession, maxStreamCount);
 }
 

Creates a new read session. A read session divides the contents of a BigQuery table into one or more streams, which can then be used to read data from the table. The read session also specifies properties of the data to be read, such as a list of columns or a push-down filter describing the rows to be returned.

A particular row can be read by at most one stream. When the caller has reached the end of each stream in the session, then all the data in the table has been read.

Data is assigned to each stream such that roughly the same number of rows can be read from each stream. Because the server-side unit for assigning data is collections of rows, the API does not guarantee that each stream will return the same number or rows. Additionally, the limits are enforced based on the number of pre-filtered rows, so some filters can lead to lopsided assignments.

Read sessions automatically expire 24 hours after they are created and do not require manual clean-up by the caller.

Sample code:

 try (BigQueryReadClient bigQueryReadClient = BigQueryReadClient.create()) {
   CreateReadSessionRequest request = CreateReadSessionRequest.newBuilder().build();
   ApiFuture<ReadSession> future = BigQueryReadClient.createReadSessionCallable().futureCall(request);
   // Do something
   ReadSession response = future.get();
 }
 

Reads rows from the stream in the format prescribed by the ReadSession. Each response contains one or more table rows, up to a maximum of 100 MiB per response; read requests which attempt to read individual rows larger than 100 MiB will fail.

Each request also returns a set of stream statistics reflecting the current state of the stream.

Sample code:

 try (BigQueryReadClient bigQueryReadClient = BigQueryReadClient.create()) {
   ReadRowsRequest request = ReadRowsRequest.newBuilder().build();

   ServerStream<ReadRowsResponse> stream = bigQueryReadClient.readRowsCallable().call(request);
   for (ReadRowsResponse response : stream) {
     // Do something when receive a response
   }
 }
 

Splits a given ReadStream into two ReadStream objects. These ReadStream objects are referred to as the primary and the residual streams of the split. The original ReadStream can still be read from in the same manner as before. Both of the returned ReadStream objects can also be read from, and the rows returned by both child streams will be the same as the rows read from the original stream.

Moreover, the two child streams will be allocated back-to-back in the original ReadStream. Concretely, it is guaranteed that for streams original, primary, and residual, that original[0-j] = primary[0-j] and original[j-n] = residual[0-m] once the streams have been read to completion.

Sample code:

 try (BigQueryReadClient bigQueryReadClient = BigQueryReadClient.create()) {
   SplitReadStreamRequest request = SplitReadStreamRequest.newBuilder().build();
   SplitReadStreamResponse response = bigQueryReadClient.splitReadStream(request);
 }
 

Splits a given ReadStream into two ReadStream objects. These ReadStream objects are referred to as the primary and the residual streams of the split. The original ReadStream can still be read from in the same manner as before. Both of the returned ReadStream objects can also be read from, and the rows returned by both child streams will be the same as the rows read from the original stream.

Moreover, the two child streams will be allocated back-to-back in the original ReadStream. Concretely, it is guaranteed that for streams original, primary, and residual, that original[0-j] = primary[0-j] and original[j-n] = residual[0-m] once the streams have been read to completion.

Sample code:

 try (BigQueryReadClient bigQueryReadClient = BigQueryReadClient.create()) {
   SplitReadStreamRequest request = SplitReadStreamRequest.newBuilder().build();
   ApiFuture<SplitReadStreamResponse> future = bigQueryReadClient.splitReadStreamCallable().futureCall(request);
   // Do something
   SplitReadStreamResponse response = future.get();
 }