SingleStore (MemSQL) connector#

The SingleStore (formerly known as MemSQL) connector allows querying and creating tables in an external SingleStore database. The SingleStore connector is very similar to the MySQL connector with the only difference being the underlying driver.

Requirements#

To connect to SingleStore, you need:

SingleStore version 7.3 or higher.
Network access from the Trino coordinator and workers to SingleStore. Port 3306 is the default port.

Configuration#

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

connector.name=memsql
connection-url=jdbc:mariadb://example.net:3306
connection-user=root
connection-password=secret

Multiple SingleStore servers#

You can have as many catalogs as you need, so if you have additional SingleStore servers, 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, Trino will create a catalog named sales using the configured connector.

General configuration properties#

The following table describes general configuration properties for the connector:

Property name	Description	Default value
`case-insensitive-name-matching`	Match schema and table names case insensitively	False
`case-insensitive-name-matching.cache-ttl`		1 minute
`metadata.cache-ttl`	Duration for which metadata, including table and column statistics, is cached	0 (disabled caching)
`metadata.cache-missing`	Cache the fact that metadata, including table and column statistics, is not available	False
`metadata.cache-maximum-size`	Maximum number of objects stored in the metadata cache	10000
`write.batch-size`	Maximum number of statements in a batched execution. Do not change this setting from the default. Non-default values may negatively impact performance.	1000
`join-pushdown.enabled`	Enable join pushdown. Equivalent catalog session property is `join_pushdown_enabled`. Enabling this may negatively impact performance for some queries.	False

Non-transactional INSERT#

The connector supports adding rows using INSERT statements. By default, data insertion is performed by writing data to a temporary table. You can skip this step to improve performance and write directly to the target table. Set the insert.non-transactional-insert.enabled catalog property or the corresponding non_transactional_insert catalog session property to true.

Note that with this property enabled, data can be corrupted in rare cases where exceptions occur during the insert operation. With transactions disabled, no rollback can be performed.

Querying SingleStore#

The SingleStore connector provides a schema for every SingleStore database. You can see the available SingleStore databases by running SHOW SCHEMAS:

SHOW SCHEMAS FROM memsql;

If you have a SingleStore database named web, you can view the tables in this database by running SHOW TABLES:

SHOW TABLES FROM memsql.web;

You can see a list of the columns in the clicks table in the web database using either of the following:

DESCRIBE memsql.web.clicks;
SHOW COLUMNS FROM memsql.web.clicks;

Finally, you can access the clicks table in the web database:

SELECT * FROM memsql.web.clicks;

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

Type mapping#

General configuration properties#

The following properties can be used to configure how data types from the connected data source are mapped to Trino data types and how the metadata is cached in Trino.

Property name

Description

Default value

unsupported-type-handling

Configure how unsupported column data types are handled:

IGNORE, column is not accessible.
CONVERT_TO_VARCHAR, column is converted to unbounded VARCHAR.

The respective catalog session property is unsupported_type_handling.

IGNORE

jdbc-types-mapped-to-varchar

Allow forced mapping of comma separated lists of data types to convert to unbounded VARCHAR

Pushdown#

The connector supports pushdown for a number of operations:

SQL support#

The connector provides read access and write access to data and metadata in a SingleStore database. In addition to the globally available and read operation statements, the connector supports the following features:

SQL DELETE#

If a WHERE clause is specified, the DELETE operation only works if the predicate in the clause can be fully pushed down to the data source.

ALTER TABLE#

The connector does not support renaming tables across multiple schemas. For example, the following statement is supported:

ALTER TABLE catalog.schema_one.table_one RENAME TO catalog.schema_one.table_two

The following statement attempts to rename a table across schemas, and therefore is not supported:

ALTER TABLE catalog.schema_one.table_one RENAME TO catalog.schema_two.table_two