openGauss Connector

The openGauss connector allows querying and creating tables in an external openGauss database. This can be used to join data between different systems like openGauss and Hive, or between two different openGauss instances.

Configuration

To configure the openGauss connector, create a catalog properties file in etc/catalog named, for example, opengauss.properties, to mount the openGauss connector as the opengauss catalog. Create the file with the following contents, replacing the connection properties as appropriate for your setup:

connector.name=openguass
connection-url=jdbc:postgresql://example.net:5432/database
connection-user=root
connection-password=secret

Multiple openGauss Databases or Servers

The openGauss connector can only access a single database within a openGauss server. Thus, if you have multiple openGauss databases, or want to connect to multiple openGauss servers, you must configure multiple instances of the openGauss connector.

To add another catalog, simply add another properties file to etc/catalog with a different name (making sure it ends in .properties). For example, if you name the property file sales.properties, openLooKeng will create a catalog named sales using the configured connector.

Querying openGauss

The openGauss connector provides a schema for every openGauss schema. You can see the available openGauss schemas by running SHOW SCHEMAS:

SHOW SCHEMAS FROM opengauss;

If you have a openGauss schema named public, you can view the tables in this schema by running SHOW TABLES:

SHOW TABLES FROM opengauss.public;

You can see a list of the columns in the hetutb table in the public database using either of the following:

DESCRIBE opengauss.public.hetutb;
SHOW COLUMNS FROM opengauss.public.hetutb;

Finally, you can access the hetutb table in the public schema:

SELECT * FROM opengauss.public.hetutb;

If you used a different name for your catalog properties file, use that catalog name instead of opengauss in the above examples.

openGauss Update/Delete Support

Create openGauss Table

Example：

CREATE TABLE opengauss_table (
    id int,
    name varchar(255));

INSERT on openGauss tables

Example：

INSERT INTO opengauss_table
  VALUES
     (1, 'Jack'),
     (2, 'Bob');

UPDATE on openGauss tables

Example：

UPDATE opengauss_table
  SET name='Tim'
  WHERE id=1;

Above example updates the column name's value to Tim of rows with column id having value 1.

SELECT result before UPDATE:

lk:default> SELECT * FROM opengauss_table;
id | name
----+------
  1 | Jack
  2 | Bob
(2 rows)

SELECT result after UPDATE

lk:default> SELECT * FROM opengauss_table;
id | name
----+------
2 | Bob
1 | Tim
(2 rows)

DELETE on openGauss tables

Example：

DELETE FROM opengauss_table
  WHERE id=2;

Above example delete the rows with column id having value 2.

SELECT result before DELETE:

lk:default> SELECT * FROM opengauss_table;
 id | name
----+------
  2 | Bob
  1 | Tim
(2 rows)

SELECT result after DELETE:

lk:default> SELECT * FROM opengauss_table;
 id | name
----+------
  1 | Tim
(1 row)

Note:

• When the compatibility type of the openGuass database is O (DBCOMPATIBILITY = A), the Date data type is not supported.

• The openGuass driver does not support put the connection in read-only mode to enable database optimization at present.

• The unit of openGauss’s Character data type is byte (e.g. n indicates to the byte length of VARCHAR(n) data type), the unit of openLooKeng’s Character data type is character (e.g. n indicates to the character length of VARCHAR(n) data type). openGauss connector does not support use create-table-as method to create a table containing Character data type directly, the byte length of Character data type needs to manually specified.

• The use-connection-pool configuration is not supported.

• Setting opengauss.metadata.speedup=true in catalog properties file can speed up DatabaseMetaData access, its default value is false.

If the subsequent version of openGuass supports the above restriction, we will make corresponding adaptation.

openGauss Connector Limitations

The following SQL statements are not yet supported:

GRANT, REVOKE, SHOW GRANTS, SHOW ROLES, SHOW ROLE GRANTS