SQL Server connector

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

Requirements

To connect to SQL Server, you need:

• SQL Server 2012 or higher, or Azure SQL Database.

• Network access from the Trino coordinator and workers to SQL Server. Port 1433 is the default port.

Configuration

The connector can query a single database on an SQL server instance. Create a catalog properties file that specifies the SQL server connector by setting the connector.name to sqlserver.

For example, to access a database as sqlserver, create the file etc/catalog/sqlserver.properties. Replace the connection properties as appropriate for your setup:

connector.name=sqlserver
connection-url=jdbc:sqlserver://<host>:<port>;database=<database>
connection-user=root
connection-password=secret

The connection-url defines the connection information and parameters to pass to the SQL Server JDBC driver. The supported parameters for the URL are available in the SQL Server JDBC driver documentation.

The connection-user and connection-password are typically required and determine the user credentials for the connection, often a service user. You can use secrets to avoid actual values in the catalog properties files.

Multiple SQL Server databases or servers

The SQL Server connector can only access a single SQL Server database within a single catalog. Thus, if you have multiple SQL Server databases, or want to connect to multiple SQL Server instances, you must configure multiple instances of the SQL Server 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, Trino creates 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 SQL Server

The SQL Server connector provides access to all schemas visible to the specified user in the configured database. For the following examples, assume the SQL Server catalog is sqlserver.

You can see the available schemas by running SHOW SCHEMAS:

SHOW SCHEMAS FROM sqlserver;

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

SHOW TABLES FROM sqlserver.web;

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

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

Finally, you can query the clicks table in the web schema:

SELECT * FROM sqlserver.web.clicks;

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

Type mapping

Trino supports the following SQL Server data types:

SQL Server Type	Trino Type
bigint	bigint
smallint	smallint
int	integer
float	double
char(n)	char(n)
varchar(n)	varchar(n)
date	date
datetime2(n)	timestamp(n)
datetimeoffset(n)	timestamp(n) with time zone

Complete list of SQL Server data types.

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

SQL support

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

• INSERT

• DELETE

• Schema and table management

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

Pushdown

The connector supports pushdown for a number of operations:

• Join pushdown

• Limit pushdown

• Top-N pushdown

Aggregate pushdown for the following functions:

• avg()

• count()

• max()

• min()

• sum()

• stddev()

• stddev_pop()

• stddev_samp()

• variance()

• var_pop()

• var_samp()

Data compression

You can specify the data compression policy for SQL Server tables with the data_compression table property. Valid policies are NONE, ROW or PAGE.

Example:

CREATE TABLE myschema.scientists (
  recordkey VARCHAR,
  name VARCHAR,
  age BIGINT,
  birthday DATE
)
WITH (
  data_compression = 'ROW'
);