CREATE PROTOCOL

Registers a custom data access protocol that can be specified when defining a LightDB-A Database external table.

Synopsis

CREATE [TRUSTED] PROTOCOL <name> (
   [readfunc='<read_call_handler>'] [, writefunc='<write_call_handler>']
   [, validatorfunc='<validate_handler>' ])

Description

CREATE PROTOCOL associates a data access protocol name with call handlers that are responsible for reading from and writing data to an external data source. You must be a superuser to create a protocol.

The CREATE PROTOCOL command must specify either a read call handler or a write call handler. The call handlers specified in the CREATE PROTOCOL command must be defined in the database.

The protocol name can be specified in a CREATE EXTERNAL TABLE command.

For information about creating and enabling a custom data access protocol, see “Example Custom Data Access Protocol” in the LightDB-A Database Administrator Guide.

Parameters

TRUSTED : If not specified, only superusers and the protocol owner can create external tables using the protocol. If specified, superusers and the protocol owner can GRANT permissions on the protocol to other database roles.

name : The name of the data access protocol. The protocol name is case sensitive. The name must be unique among the protocols in the database.

readfunc= ‘read_call_handler’ : The name of a previously registered function that LightDB-A Database calls to read data from an external data source. The command must specify either a read call handler or a write call handler.

writefunc= 'write_call_handler’ : The name of a previously registered function that LightDB-A Database calls to write data to an external data source. The command must specify either a read call handler or a write call handler.

validatorfunc='validate_handler’ : An optional validator function that validates the URL specified in the CREATE EXTERNAL TABLE command.

Notes

LightDB-A Database handles external tables of type file, gpfdist, and gpfdists internally. See s3:// Protocol for information about enabling the S3 protocol. Refer to pxf:// Protocol for information about using the pxf protocol.

Any shared library that implements a data access protocol must be located in the same location on all LightDB-A Database segment hosts. For example, the shared library can be in a location specified by the operating system environment variable LD_LIBRARY_PATH on all hosts. You can also specify the location when you define the handler function. For example, when you define the s3 protocol in the CREATE PROTOCOL command, you specify $libdir/gps3ext.so as the location of the shared object, where $libdir is located at $GPHOME/lib.

Compatibility