2 Using the BigQuery Handler

The BigQuery Handler supports the standard SQL data types and most of these data types are supported by the BigQuery Handler. A data type conversion from the column value in the trail file to the corresponding Java type representing the BigQuery column type in the BigQuery Handler is required.

The following data types are supported:

STRING
BYTES
INTEGER
FLOAT
NUMERIC
BOOLEAN
TIMESTAMP
DATE
TIME
DATETIME

The BigQuery Handler does not support complex data types, such as ARRAY and STRUCT.

You can configure the BigQuery Handler in one of these two modes:

auditLogMode = true

When the handler is configured to run with Audit log mode, the data is pushed into Google BigQuery without a unique id and primary key. As a result, Google BigQuery is not able to merge different operations on the same row.

Also, the order in which the audit log is displayed in the BigQuery data set is not deterministic.

To overcome these limitations, you need to specify optype and position in the meta columns template for the handler. This adds two columns of the same names in the schema for the table in Google BigQuery. For example:

gg.handler.bigquery.metaColumnsTemplate = ${optype}, ${position}

The optype is important to determine the operation type for the row in the audit log.

To view the audit log in order of the operations processed in the trail file, specify position which can be used in the ORDER BY clause while querying the table in Google BigQuery. For example:

SELECT * FROM [projectId:datasetId.tableId] ORDER BY position

auditLogMode = false

This causes the handler to write data into Google BigQuery specifying a unique id and primary key for each row. As a result, Google BigQuery is able to merge different operations on the same row.

The trail source needs to have a full image of the records in order to merge correctly.

Google BigQuery processes every operation as an insert for each row. As a result, there is a deleted column added to the schema for the table in this mode of operation. When the handler encounters a delete operation on a row, it inserts the row into Google BigQuery and sets the deleted column to true.

To view data in the BigQuery table like it would ideally be seen in a RDBMS, specify a WHERE deleted = false clause while querying the table in Google BigQuery.

The BigQuery Handler pushes operations to Google BigQuery using synchronous API. Insert, update, and delete operations are processed differently in BigQuery than in a traditional RDBMS.

The following explains how insert, update, and delete operations are interpreted by the handler depending on the mode of operation:

auditLogMode = true

• insert – Inserts the record with optype as an insert operation in the BigQuery table.

• update –Inserts the record with optype as an update operation in the BigQuery table.

• delete – Inserts the record with optype as a delete operation in the BigQuery table.

• pkUpdate—When pkUpdateHandling property is configured as delete-insert, the handler sends out a delete operation followed by an insert operation. Both these rows have the same position in the BigQuery table, which helps to identify it as a primary key operation and not a separate delete and insert operation.

auditLogMode = false

• insert – If the row does not already exist in Google BigQuery, then an insert operation is processed as an insert. If the row already exists in Google BigQuery, then an insert operation is processed as an update. The handler sets the deleted column to false.

• update –If a row does not exist in Google BigQuery, then an update operation is processed as an insert. If the row already exists in Google BigQuery, then an update operation is processed as update. The handler sets the deleted column to false.

• delete – If the row does not exist in Google BigQuery, then a delete operation has no effect. If the row exists in Google BigQuery, then a delete operation is processed as a delete. The handler sets the deleted column to true.

• pkUpdate—When pkUpdateHandling property is configured as delete-insert, the handler sets the deleted column to true for the row whose primary key is updated. It is followed by a separate insert operation with the new primary key and the deleted column set to false for this row.

Do not toggle the audit log mode because it forces the BigQuery handler to abend as Google BigQuery cannot alter schema of an existing table. The existing table needs to be deleted before switching audit log modes.

The following are the configurable values for the BigQuery Handler. These properties are located in the Java Adapter properties file (not in the Replicat properties file).

To enable the selection of the BigQuery Handler, you must first configure the handler type by specifying gg.handler.jdbc.type=bigquery and the other BigQuery properties as follows:

To connect to BigQuery using a proxy server, you must configure the proxy host and the proxy port in the properties file as follows:

javawriter.bootoptions= -Dhttps.proxyHost=proxy_host_name
                                                -Dhttps.proxyPort=proxy_port_number

You have to configure the BigQuery Handler authentication using the credentials in the JSON file downloaded from Google BigQuery.

Download the credentials file:

1. Login into your Google account at cloud.google.com.

2. Click Console, and then to go to the Dashboard where you can select your project.

3. From the navigation menu, click APIs & Services then select Credentials.

4. From the Create Credentials menu, choose Service account key.

5. Choose the JSON key type to download the JSON credentials file for your system.

Once you have the credentials file, you can authenticate the handler in one of these two ways:

• Specify the path to the credentials file in the properties file with the gg.handler.name.credentialsFile configuration property.

  The path of the credentials file must contain the path with no wildcard appended. If you include the * wildcard in the path to the credentials file, the file is not recognized.

  Or

• Set the GOOGLE_APPLICATION_CREDENTIALS environment variable on your system. For example:

  export GOOGLE_APPLICATION_CREDENTIALS = credentials.json
  

  Then restart the Oracle GoldenGate manager process.