Starburst IBM DB2 connector

The IBM DB2 connector allows querying and creating tables in an external DB2 database.

Requirements

To connect to IBM DB2, you need:

• DB2 11.5 or higher for Linux, Unix, and Windows (LUW).

• Network access from the coordinator and workers to the DB2 server. Port 51000 is the default port.

• A valid Starburst Enterprise license.

Configuration

Any of the below installation and configuration methods require the following artifacts:

• DB2 JDBC driver file db2jcc-db2jcc4.jar obtained from IBM

• JDBC connection details to connect to DB2 in a catalog properties file (e.g. db2.properties for a catalog named db2). File should contain the following contents, replacing the connection properties as appropriate for your setup:

connector.name=db2
connection-url=jdbc:db2://HOST:PORT/DATABASE
connection-user=USERNAME
connection-password=PASSWORD

The DB2 JDBC driver documentation contains information about format and parameters of the JDBC URL.

To install the DB2 Database connector, use the following steps:

1. Add the DB2 JDBC driver JAR files to the plugin/db2 directory.

2. Add a catalog properties file (e.g. db2.properties for a catalog named db2).

3. Perform the above steps on every node.

4. Restart SEP on every node.

Type mapping

Because SEP and DB2 each support types that the other does not, this connector modifies some types when reading or writing data.

Type mapping for reading data

The connector supports reading the following DB2 types and performs conversion to PrestoSQL types with the detailed mappings.

DB2 to Trino type mapping

DB2 type	Trino type	Notes
NUMERIC	DECIMAL(p, s)
DECIMAL(p, s)	DECIMAL(p, s)
DECFLOAT(p)	DECIMAL(p, s)
FLOAT[(p)]	DOUBLE
REAL	REAL
DOUBLE	DOUBLE
DOUBLE PRECISION	DOUBLE
TINYINT	SMALLINT
SMALLINT	SMALLINT
INT	INT
BIGINT	BIGINT
DOUBLE PRECISION	DOUBLE
VARCHAR(n)	VARCHAR(n)
CHAR VARYING(n)	VARCHAR(n)
BINARY(n)	VARBINARY
BINARY VARYING	VARBINARY
VARBINARY(n)	VARBINARY
CHAR(n)	CHAR(n)
CLOB	VARCHAR
BLOB	VARBINARY
ROWID	VARCHAR
DATE	DATE	See Mapping datetime types
TIMESTAMP(p)	TIMESTAMP(3)	See Mapping datetime types
TIME	TIME	See Mapping datetime types

Type mapping for writing data

The connector supports writing the following Trino types and performs conversion to DB2 types with the detailed mappings.

Trino to DB2 type mapping

Trino type	DB2 type	Notes
BOOLEAN	BOOLEAN
TINYINT	SMALLINT
SMALLINT	SMALLINT
INTEGER	INTEGER
BIGINT	BIGINT
REAL	FLOAT(23)
DOUBLE	FLOAT(53)
DECIMAL(p, s)	DECIMAL(p, s)
VARCHAR(n)	VARCHAR(n)	For n up to 32704.
VARCHAR(n)	CLOB	For n above 32704.
VARCHAR	CLOB	When no bound is given.
CHAR(n)	CHAR(n)	For n up to 255. n above 255 is not supported.
VARBINARY	BLOB
TIMESTAMP	TIMESTAMP	See Mapping datetime types
TIME	TIME	See Mapping datetime types
DATE	DATE	See Mapping datetime types

Mapping datetime types

The DB2 connector does not currently support variable-precision timestamps.

Selecting a DB2 timestamp value with fractional second precision greater than 3 truncates (not rounds) the fractional seconds to three digits.

Inserting a TIME value with fractional seconds into DB2 truncates (not rounds) the time to second precision, as DB2 does not support fractional seconds in TIME values.

Warning

Because of differences in date and time representation in DB2 and JDBC, attempting to insert or select a datetime value earlier than 1582-10-15 results in an incorrect date being stored/retrieved.

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
case-insensitive-name-matching	Support case insensitive database and collection names	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

SQL support

The connector provides read and write access to data and metadata in the DB2 database. In addition to the globally available and read operation statements, the connector supports the following features:

• INSERT

• DELETE

• CREATE TABLE

• CREATE TABLE AS

• DROP TABLE

• ALTER TABLE

• CREATE SCHEMA

• DROP SCHEMA

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.

Performance

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

Table statistics

The DB2 connector supports table and column statistics to improve query processing performance based on the actual data in the data source.

The statistics are collected by DB2 and retrieved by the connector.

To collect statistics for a table, execute the following statements in DB2.

CALL SYSPROC.ADMIN_CMD('RUNSTATS ON TABLE table_name');

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()

• covar_samp()

• covar_pop()

• stddev() and stddev_samp()

• stddev_pop()

• var_pop()

• variance() and var_samp()

Dynamic filtering

Dynamic filtering is enabled by default. It causes the connector to wait for dynamic filtering to complete before starting a JDBC query.

You can disable dynamic filtering by setting the property dynamic-filtering.enabled in your catalog properties file to false.

JDBC connection pooling

You can improve performance by enabling JDBC connection pooling, which is disabled by default.

Starburst Cached Views

The connectors supports table scan redirection to improve performance and reduce load on the data source.

Security

The connector includes a number of security-related features, detailed in the following sections.

User impersonation

DB2 connector supports user impersonation.

User impersonation can be enabled in your catalog file:

db2.impersonation.enabled=true

User impersonation is based on SET SESSION_USER detailed in the IBM documentation.

Note

Running SET SESSION_USER in DB2 requires the user to have a SETSESSIONUSER privilege.

Password credential pass-through

The connector supports password credential pass-through. To enable it, edit the catalog properties file to include the authentication type:

db2.authentication.type=PASSWORD_PASS_THROUGH

For more information about configurations and limitations, see Password credential pass-through.