com.google.cloud.dataflow.sdk.io

Class BigQueryIO

java.lang.Object

com.google.cloud.dataflow.sdk.io.BigQueryIO

public class BigQueryIO
extends Object

PTransforms for reading and writing BigQuery tables.

Table References

A fully-qualified BigQuery table name consists of three components:

• projectId: the Cloud project id (defaults to GcpOptions.getProject()).
• datasetId: the BigQuery dataset id, unique within a project.
• tableId: a table id, unique within a dataset.

BigQuery table references are stored as a TableReference, which comes from the BigQuery Java Client API. Tables can be referred to as Strings, with or without the projectId. A helper function is provided (parseTableSpec(String)) that parses the following string forms into a TableReference:

• [project_id]:[dataset_id].[table_id]
• [dataset_id].[table_id]

Reading

To read from a BigQuery table, apply a BigQueryIO.Read transformation. This produces a PCollection of TableRows as output:

 PCollection<TableRow> shakespeare = pipeline.apply(
     BigQueryIO.Read.named("Read")
                    .from("clouddataflow-readonly:samples.weather_stations"));
 

See TableRow for more information on the TableRow object.

Users may provide a query to read from rather than reading all of a BigQuery table. If specified, the result obtained by executing the specified query will be used as the data of the input transform.

 PCollection<TableRow> shakespeare = pipeline.apply(
     BigQueryIO.Read.named("Read")
                    .fromQuery("SELECT year, mean_temp FROM [samples.weather_stations]"));
 

When creating a BigQuery input transform, users should provide either a query or a table. Pipeline construction will fail with a validation error if neither or both are specified.

Writing

To write to a BigQuery table, apply a BigQueryIO.Write transformation. This consumes a PCollection of TableRows as input.

 PCollection<TableRow> quotes = ...

 List<TableFieldSchema> fields = new ArrayList<>();
 fields.add(new TableFieldSchema().setName("source").setType("STRING"));
 fields.add(new TableFieldSchema().setName("quote").setType("STRING"));
 TableSchema schema = new TableSchema().setFields(fields);

 quotes.apply(BigQueryIO.Write
     .named("Write")
     .to("my-project:output.output_table")
     .withSchema(schema)
     .withWriteDisposition(BigQueryIO.Write.WriteDisposition.WRITE_TRUNCATE));
 

See BigQueryIO.Write for details on how to specify if a write should append to an existing table, replace the table, or verify that the table is empty. Note that the dataset being written to must already exist. Write dispositions are not supported in streaming mode.

Sharding BigQuery output tables

A common use case is to dynamically generate BigQuery table names based on the current window. To support this, BigQueryIO.Write.to(SerializableFunction) accepts a function mapping the current window to a tablespec. For example, here's code that outputs daily tables to BigQuery:

 PCollection<TableRow> quotes = ...
 quotes.apply(Window.<TableRow>into(CalendarWindows.days(1)))
       .apply(BigQueryIO.Write
         .named("Write")
         .withSchema(schema)
         .to(new SerializableFunction<BoundedWindow, String>() {
           public String apply(BoundedWindow window) {
             // The cast below is safe because CalendarWindows.days(1) produces IntervalWindows.
             String dayString = DateTimeFormat.forPattern("yyyy_MM_dd")
                  .withZone(DateTimeZone.UTC)
                  .print(((IntervalWindow) window).start());
             return "my-project:output.output_table_" + dayString;
           }
         }));
 

Per-window tables are not yet supported in batch mode.

Permissions

Permission requirements depend on the PipelineRunner that is used to execute the Dataflow job. Please refer to the documentation of corresponding PipelineRunners for more details.

Please see BigQuery Access Control for security and permission related information specific to BigQuery.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BigQueryIO.Read A PTransform that reads from a BigQuery table and returns a PCollection of TableRows containing each of the rows of the table.
static class	BigQueryIO.Write A PTransform that writes a PCollection containing TableRows to a BigQuery table.

Field Summary

Fields

Modifier and Type	Field and Description
static String	SET_PROJECT_FROM_OPTIONS_WARNING Deprecated.

Method Summary

Modifier and Type	Method and Description
static TableReference	parseTableSpec(String tableSpec) Parse a table specification in the form "[project_id]:[dataset_id].[table_id]" or "[dataset_id].[table_id]".
static String	toTableSpec(TableReference ref) Returns a canonical string representation of the TableReference.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SET_PROJECT_FROM_OPTIONS_WARNING

@Deprecated
public static final String SET_PROJECT_FROM_OPTIONS_WARNING

Deprecated.

See Also:

Constant Field Values

Method Detail

parseTableSpec

public static TableReference parseTableSpec(String tableSpec)

Parse a table specification in the form "[project_id]:[dataset_id].[table_id]" or "[dataset_id].[table_id]".

If the project id is omitted, the default project id is used.

toTableSpec

public static String toTableSpec(TableReference ref)

Returns a canonical string representation of the TableReference.