Query Hybrid Partitioned Data

If you want to query internal data and multiple data files in the Object Store as single logical table you can use a hybrid partitioned table to represent the data as single object. Use the procedure DBMS_CLOUD.CREATE_HYBRID_PART_TABLE to create a hybrid partitioned table.

If your data, internal or external, can be represented in finer granularity as multiple logical partitions then it is highly recommended to create a hybrid partitioned table with multiple internal and external partitions, preserving the logical partitioning of your data for query access.

When you a create a hybrid partitioned table, you include a partitioning clause in the DBMS_CLOUD.CREATE_HYBRID_PART_TABLE statement. The partitioning clause that you include depends upon your data files and the type of partitioning you use. See Creating Hybrid Partitioned Tables for more information.

  1. Store your object store credentials using the procedure DBMS_CLOUD.CREATE_CREDENTIAL.

    For example:

        credential_name => 'DEF_CRED_NAME',
        username => 'adb_user@example.com',
        password => 'password' );

    Creating a credential to access Oracle Cloud Infrastructure Object Store is not required if you enable resource principal credentials. See Use Resource Principal to Access Oracle Cloud Infrastructure Resources for more information.

    This operation stores the credentials in the database in an encrypted format. You can use any name for the credential name. Note that this step is required only once unless your object store credentials change. Once you store the credentials you can then use the same credential name for creating hybrid partitioned tables.

    See CREATE_CREDENTIAL Procedure for information about the username and password parameters for different object storage services.

  2. Create a hybrid partitioned table on top of your source files using the procedure DBMS_CLOUD.CREATE_HYBRID_PART_TABLE.

    The procedure DBMS_CLOUD.CREATE_HYBRID_PART_TABLE supports external partitioned files in the supported cloud object storage services. The credential is a table level property; therefore, the external files must be on the same object store.

    For example:

          table_name =>'HPT1',  
          credential_name =>'DEF_CRED_NAME',  
          format => json_object('delimiter' value ',', 'recorddelimiter' value 'newline', 'characterset' value 'us7ascii'),  
          column_list => 'col1 number, col2 number, col3 number',
          partitioning_clause => 'partition by range (col1)
               (partition p1 values less than (1000) external location
                  ( ''https://objectstorage.us-phoenix-1.oraclecloud.com/n/namespace-string/b/bucketname/o/file_11.txt'') ,
                partition p2 values less than (2000) external location
                  ( ''https://objectstorage.us-phoenix-1.oraclecloud.com/n/namespace-string/b/bucketname/o/file_21.txt'') ,
                partition p3 values less than (3000) )'

    The parameters are:

    • table_name: is the hybrid partitioned table name.

    • credential_name: is the name of the credential created in the previous step.

    • partitioning_clause: is the complete partitioning clause, including the location information for individual partitions.

    • format: defines the options you can specify to describe the format of the source file.

    • column_list: is a comma delimited list of the column definitions in the source files.

    In this example, namespace-string is the Oracle Cloud Infrastructure object storage namespace and bucketname is the bucket name. See Understanding Object Storage Namespaces for more information.

    You can now run queries on the hybrid partitioned table you created in the previous step. Your Autonomous Database takes advantage of the partitioning information of your hybrid partitioned table, ensuring that the query only accesses relevant data files in the Object Store. For example, the following query only reads data files from partition P1:

    SELECT * FROM hpt1 WHERE col1 < 750;

    The hybrid partitioned tables you create with DBMS_CLOUD.CREATE_HYBRID_PART_TABLE include two invisible columns file$path and file$name. These columns help identify which file a record is coming from. See External Table Metadata Columns for more information.

    If there are any rows in the source files that do not match the format options you specified, the query reports an error. You can use DBMS_CLOUD parameters, like rejectlimit, to suppress these errors. As an alternative, you can also validate the hybrid partitioned table you created to see the error messages and the rejected rows so that you can change your format options accordingly. See Validate External Data and Validate Hybrid Partitioned Data for more information.

    See CREATE_HYBRID_PART_TABLE Procedure detailed information about the parameters.

    See DBMS_CLOUD Package File URI Formats for more information on the supported cloud object storage services.