Ignite connector#

The Ignite connector allows querying an Apache Ignite database from Trino.

Requirements#

To connect to a Ignite server, you need:

Ignite version 2.9.0 or latter
Network access from the Trino coordinator and workers to the Ignite server. Port 10800 is the default port.
Specify --add-opens=java.base/java.nio=ALL-UNNAMED in the jvm.config when starting the Trino server.

Configuration#

The Ignite connector expose public schema by default.

The connector can query a Ignite instance. Create a catalog properties file that specifies the Ignite connector by setting the connector.name to ignite.

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

connector.name=ignite
connection-url=jdbc:ignite:thin://host1:10800/
connection-user=exampleuser
connection-password=examplepassword

The connection-url defines the connection information and parameters to pass to the Ignite JDBC driver. The parameters for the URL are available in the Ignite JDBC driver documentation. Some parameters can have adverse effects on the connector behavior or not work with the connector.

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 Ignite servers#

If you have multiple Ignite servers you need to configure one catalog for each server. To add another catalog:

Add another properties file to etc/catalog
Save it with a different name that ends in .properties

For example, if you name the property file sales.properties, Trino uses the configured connector to create a catalog named sales.

General configuration properties#

The following table describes general catalog configuration properties for the connector:

Property name	Description
`case-insensitive-name-matching`	Support case insensitive schema and table names. Defaults to `false`.
`case-insensitive-name-matching.cache-ttl`	Duration for which case insensitive schema and table names are cached. Defaults to `1m`.
`case-insensitive-name-matching.config-file`	Path to a name mapping configuration file in JSON format that allows Trino to disambiguate between schemas and tables with similar names in different cases. Defaults to `null`.
`case-insensitive-name-matching.config-file.refresh-period`	Frequency with which Trino checks the name matching configuration file for changes. The duration value defaults to `0s` (refresh disabled).
`metadata.cache-ttl`	Duration for which metadata, including table and column statistics, is cached. Defaults to `0s` (caching disabled).
`metadata.cache-missing`	Cache the fact that metadata, including table and column statistics, is not available. Defaults to `false`.
`metadata.schemas.cache-ttl`	Duration for which schema metadata is cached. Defaults to the value of `metadata.cache-ttl`.
`metadata.tables.cache-ttl`	Duration for which table metadata is cached. Defaults to the value of `metadata.cache-ttl`.
`metadata.statistics.cache-ttl`	Duration for which tables statistics are cached. Defaults to the value of `metadata.cache-ttl`.
`metadata.cache-maximum-size`	Maximum number of objects stored in the metadata cache. Defaults to `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. Defaults to `1000`.
`dynamic-filtering.enabled`	Push down dynamic filters into JDBC queries. Defaults to `true`.
`dynamic-filtering.wait-timeout`	Maximum duration for which Trino waits for dynamic filters to be collected from the build side of joins before starting a JDBC query. Using a large timeout can potentially result in more detailed dynamic filters. However, it can also increase latency for some queries. Defaults to `20s`.

Appending query metadata#

The optional parameter query.comment-format allows you to configure a SQL comment that is sent to the datasource with each query. The format of this comment can contain any characters and the following metadata:

$QUERY_ID: The identifier of the query.
$USER: The name of the user who submits the query to Trino.
$SOURCE: The identifier of the client tool used to submit the query, for example trino-cli.
$TRACE_TOKEN: The trace token configured with the client tool.

The comment can provide more context about the query. This additional information is available in the logs of the datasource. To include environment variables from the Trino cluster with the comment , use the ${ENV:VARIABLE-NAME} syntax.

The following example sets a simple comment that identifies each query sent by Trino:

query.comment-format=Query sent by Trino.

With this configuration, a query such as SELECT * FROM example_table; is sent to the datasource with the comment appended:

SELECT * FROM example_table; /*Query sent by Trino.*/

The following example improves on the preceding example by using metadata:

query.comment-format=Query $QUERY_ID sent by user $USER from Trino.

If Jane sent the query with the query identifier 20230622_180528_00000_bkizg, the following comment string is sent to the datasource:

SELECT * FROM example_table; /*Query 20230622_180528_00000_bkizg sent by user Jane from Trino.*/

Note

Certain JDBC driver settings and logging configurations might cause the comment to be removed.

Domain compaction threshold#

Pushing down a large list of predicates to the data source can compromise performance. Trino compacts large predicates into a simpler range predicate by default to ensure a balance between performance and predicate pushdown. If necessary, the threshold for this compaction can be increased to improve performance when the data source is capable of taking advantage of large predicates. Increasing this threshold may improve pushdown of large dynamic filters. The domain-compaction-threshold catalog configuration property or the domain_compaction_threshold catalog session property can be used to adjust the default value of 1000 for this threshold.

Procedures#

system.flush_metadata_cache()

Flush JDBC metadata caches. For example, the following system call flushes the metadata caches for all schemas in the example catalog
```
USE example.example_schema;
CALL system.flush_metadata_cache();
```

Case insensitive matching#

When case-insensitive-name-matching is set to true, Trino is able to query non-lowercase schemas and tables by maintaining a mapping of the lowercase name to the actual name in the remote system. However, if two schemas and/or tables have names that differ only in case (such as “customers” and “Customers”) then Trino fails to query them due to ambiguity.

In these cases, use the case-insensitive-name-matching.config-file catalog configuration property to specify a configuration file that maps these remote schemas/tables to their respective Trino schemas/tables:

{
  "schemas": [
    {
      "remoteSchema": "CaseSensitiveName",
      "mapping": "case_insensitive_1"
    },
    {
      "remoteSchema": "cASEsENSITIVEnAME",
      "mapping": "case_insensitive_2"
    }],
  "tables": [
    {
      "remoteSchema": "CaseSensitiveName",
      "remoteTable": "tablex",
      "mapping": "table_1"
    },
    {
      "remoteSchema": "CaseSensitiveName",
      "remoteTable": "TABLEX",
      "mapping": "table_2"
    }]
}

Queries against one of the tables or schemes defined in the mapping attributes are run against the corresponding remote entity. For example, a query against tables in the case_insensitive_1 schema is forwarded to the CaseSensitiveName schema and a query against case_insensitive_2 is forwarded to the cASEsENSITIVEnAME schema.

At the table mapping level, a query on case_insensitive_1.table_1 as configured above is forwarded to CaseSensitiveName.tablex, and a query on case_insensitive_1.table_2 is forwarded to CaseSensitiveName.TABLEX.

By default, when a change is made to the mapping configuration file, Trino must be restarted to load the changes. Optionally, you can set the case-insensitive-name-mapping.refresh-period to have Trino refresh the properties without requiring a restart:

case-insensitive-name-mapping.refresh-period=30s

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.

Table properties#

Table property usage example:

CREATE TABLE public.person (
  id BIGINT NOT NULL,
  birthday DATE NOT NULL,
  name VARCHAR(26),
  age BIGINT,
  logdate DATE
)
WITH (
  primary_key = ARRAY['id', 'birthday']
);

The following are supported Ignite table properties from https://ignite.apache.org/docs/latest/sql-reference/ddl

Property name	Required	Description
`primary_key`	No	The primary key of the table, can chose multi columns as the table primary key. Table at least contains one column not in primary key.

`primary_key`#

This is a list of columns to be used as the table’s primary key. If not specified, a VARCHAR primary key column named DUMMY_ID is generated, the value is derived from the value generated by the UUID function in Ignite.

Type mapping#

The following are supported Ignite SQL data types from https://ignite.apache.org/docs/latest/sql-reference/data-types

Ignite SQL data type name	Map to Trino type	Possible values
`BOOLEAN`	`BOOLEAN`	`TRUE` and `FALSE`
`BIGINT`	`BIGINT`	`-9223372036854775808`, `9223372036854775807`, etc.
`DECIMAL`	`DECIMAL`	Data type with fixed precision and scale
`DOUBLE`	`DOUBLE`	`3.14`, `-10.24`, etc.
`INT`	`INT`	`-2147483648`, `2147483647`, etc.
`REAL`	`REAL`	`3.14`, `-10.24`, etc.
`SMALLINT`	`SMALLINT`	`-32768`, `32767`, etc.
`TINYINT`	`TINYINT`	`-128`, `127`, etc.
`CHAR`	`CHAR`	`hello`, `Trino`, etc.
`VARCHAR`	`VARCHAR`	`hello`, `Trino`, etc.
`DATE`	`DATE`	`1972-01-01`, `2021-07-15`, etc.
`BINARY`	`VARBINARY`	Represents a byte array.

SQL support#

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

UPDATE#

Only UPDATE statements with constant assignments and predicates are supported. For example, the following statement is supported because the values assigned are constants:

UPDATE table SET col1 = 1 WHERE col3 = 1

Arithmetic expressions, function calls, and other non-constant UPDATE statements are not supported. For example, the following statement is not supported because arithmetic expressions cannot be used with the SET command:

UPDATE table SET col1 = col2 + 2 WHERE col3 = 1

The =, !=, >, <, >=, <=, IN, NOT IN operators are supported in predicates. The following statement is not supported because the AND operator cannot be used in predicates:

UPDATE table SET col1 = 1 WHERE col3 = 1 AND col2 = 3

All column values of a table row cannot be updated simultaneously. For a three column table, the following statement is not supported:

UPDATE table SET col1 = 1, col2 = 2, col3 = 3 WHERE col3 = 1

ALTER TABLE RENAME TO#

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

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

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

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

Pushdown#

The connector supports pushdown for a number of operations:

Aggregate pushdown for the following functions:

Predicate pushdown support#

The connector does not support pushdown of any predicates on columns with textual types like CHAR or VARCHAR. This ensures correctness of results since the data source may compare strings case-insensitively.

In the following example, the predicate is not pushed down for either query since name is a column of type VARCHAR:

SELECT * FROM nation WHERE name > 'CANADA';
SELECT * FROM nation WHERE name = 'CANADA';