Exasol connector

The Exasol connector allows querying an Exasol database.

Requirements

To connect to Exasol, you need:

• Exasol database version 8.34.0 or higher.
• Network access from the Trino coordinator and workers to Exasol. Port 8563 is the default port.

Configuration

To configure the Exasol connector as the example catalog, create a file named example.properties in etc/catalog. Include the following connection properties in the file:

connector.name=exasol
connection-url=jdbc:exa:exasol.example.com:8563
connection-user=user
connection-password=secret

The connection-url defines the connection information and parameters to pass to the JDBC driver. See the Exasol JDBC driver documentation for more information.

The connection-user and connection-password are typically required and determine the user credentials for the connection, often a service user. You can use {doc}secrets </security/secrets> to avoid using actual values in catalog properties files.

:::{note} If your Exasol database uses a self-signed TLS certificate you must specify the certificate's fingerprint in the JDBC URL using parameter fingerprint, e.g.: jdbc:exa:exasol.example.com:8563;fingerprint=ABC123. :::

(exasol-type-mapping)=

Type mapping

Because Trino and Exasol each support types that the other does not, this connector {ref}modifies some types <type-mapping-overview> when reading data. Data types may not map the same way in both directions between Trino and the data source. Refer to the following sections for type mapping in each direction.

Exasol to Trino type mapping

Trino supports selecting Exasol database types. This table shows the Exasol to Trino data type mapping:

:::{list-table} Exasol to Trino type mapping :widths: 25, 25, 50 :header-rows: 1

• • Exasol database type
  • Trino type
  • Notes
• • BOOLEAN
  • BOOLEAN
• • DOUBLE PRECISION
  • REAL
• • DECIMAL(p, s)
  • DECIMAL(p, s)
  • See {ref}exasol-number-mapping
• • CHAR(n)
  • CHAR(n)
• • VARCHAR(n)
  • VARCHAR(n)
• • DATE
  • DATE
• • HASHTYPE
  • VARBINARY

:::

No other types are supported.

(exasol-number-mapping)=

Mapping numeric types

An Exasol DECIMAL(p, s) maps to Trino's DECIMAL(p, s) and vice versa except in these conditions:

• No precision is specified for the column (example: DECIMAL or DECIMAL(*)).
• Scale (s) is greater than precision.
• Precision (p) is greater than 36.
• Scale is negative.

(exasol-character-mapping)=

Mapping character types

Trino's VARCHAR(n) maps to VARCHAR(n) and vice versa if n is no greater than 2000000. Exasol does not support longer values. If no length is specified, the connector uses 2000000.

Trino's CHAR(n) maps to CHAR(n) and vice versa if n is no greater than 2000. Exasol does not support longer values.

(exasol-sql-support)=

SQL support

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

(exasol-procedures)=

Procedures

(exasol-table-functions)=

Table functions

The connector provides specific {doc}table functions </functions/table> to access Exasol.

(exasol-query-function)=

query(varchar) -> table

The query function allows you to query the underlying database directly. It requires syntax native to Exasol, because the full query is pushed down and processed in Exasol. This can be useful for accessing native features which are not available in Trino or for improving query performance in situations where running a query natively may be faster.

As a simple example, query the example catalog and select an entire table::

SELECT
  *
FROM
  TABLE(
    example.system.query(
      query => 'SELECT
        *
      FROM
        tpch.nation'
    )
  );

As a practical example, you can use the WINDOW clause from Exasol:

SELECT
  *
FROM
  TABLE(
    example.system.query(
      query => 'SELECT
        id, department, hire_date, starting_salary,
        AVG(starting_salary) OVER w2 AVG,
        MIN(starting_salary) OVER w2 MIN_STARTING_SALARY,
        MAX(starting_salary) OVER (w1 ORDER BY hire_date)
      FROM employee_table
      WINDOW w1 as (PARTITION BY department), w2 as (w1 ORDER BY hire_date)
      ORDER BY department, hire_date'
    )
  );

Performance

The connector includes a number of performance improvements, detailed in the following sections.

(exasol-pushdown)=

Pushdown

The connector supports pushdown for a number of operations:

• {ref}limit-pushdown
• {ref}topn-pushdown