Redis коннектор#

Примечание

Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.

The Redis connector allows querying of live data stored in Redis. This can be used to join data between different systems like Redis and Hive.

Each Redis key/value pair is presented as a single row in Trino. Rows can be broken down into cells by using table definition files.

Currently, only Redis key of string and zset types are supported, only Redis value of string and hash types are supported.

Требования#

Requirements for using the connector in a catalog to connect to a Redis data source are:

Redis 2.8.0 or higher (Redis Cluster is not supported)
Network access, by default on port 6379, from the Trino coordinator and workers to Redis.

Конфигурация#

To configure the Redis connector, create a catalog properties file etc/catalog/example.properties with the following content, replacing the properties as appropriate:

connector.name=redis
redis.table-names=schema1.table1,schema1.table2
redis.nodes=host:port

Multiple Redis servers#

You can have as many catalogs as you need. If you have additional Redis servers, simply add another properties file to etc/catalog with a different name, making sure it ends in .properties.

Configuration properties#

The following configuration properties are available:

Property name	Description
`redis.table-names`	List of all tables provided by the catalog
`redis.default-schema`	Default schema name for tables
`redis.nodes`	Location of the Redis server
`redis.scan-count`	Redis parameter for scanning of the keys
`redis.max-keys-per-fetch`	Get values associated with the specified number of keys in the redis command such as MGET(key…)
`redis.key-prefix-schema-table`	Redis keys have schema-name:table-name prefix
`redis.key-delimiter`	Delimiter separating schema_name and table_name if redis.key-prefix-schema-table is used
`redis.table-description-dir`	Directory containing table description files
`redis.table-description-cache-ttl`	The cache time for table description files
`redis.hide-internal-columns`	Controls whether internal columns are part of the table schema or not
`redis.database-index`	Redis database index
`redis.user`	Redis server username
`redis.password`	Redis server password

`redis.table-names`#

Comma-separated list of all tables provided by this catalog. A table name can be unqualified (simple name) and is placed into the default schema (see below), or qualified with a schema name (<schema-name>.<table-name>).

For each table defined, a table description file (see below) may exist. If no table description file exists, the table only contains internal columns (see below).

This property is optional; the connector relies on the table description files specified in the redis.table-description-dir property.

`redis.default-schema`#

Defines the schema which will contain all tables that were defined without a qualifying schema name.

This property is optional; the default is default.

`redis.nodes`#

The hostname:port pair for the Redis server.

This property is required; there is no default.

Redis Cluster is not supported.

`redis.scan-count`#

The internal COUNT parameter for the Redis SCAN command when connector is using SCAN to find keys for the data. This parameter can be used to tune performance of the Redis connector.

This property is optional; the default is 100.

`redis.max-keys-per-fetch`#

The internal number of keys for the Redis MGET command and Pipeline HGETALL command when connector is using these commands to find values of keys. This parameter can be used to tune performance of the Redis connector.

This property is optional; the default is 100.

`redis.key-prefix-schema-table`#

If true, only keys prefixed with the schema-name:table-name are scanned for a table, and all other keys are filtered out. If false, all keys are scanned.

This property is optional; the default is false.

`redis.key-delimiter`#

The character used for separating schema-name and table-name when redis.key-prefix-schema-table is true

This property is optional; the default is :.

`redis.table-description-dir`#

References a folder within Trino deployment that holds one or more JSON files, which must end with .json and contain table description files.

Note that the table description files will only be used by the Trino coordinator node.

This property is optional; the default is etc/redis.

`redis.table-description-cache-ttl`#

The Redis connector dynamically loads the table description files after waiting for the time specified by this property. Therefore, there is no need to update the redis.table-names property and restart the Trino service when adding, updating, or deleting a file end with .json to redis.table-description-dir folder.

This property is optional; the default is 5m.

`redis.hide-internal-columns`#

In addition to the data columns defined in a table description file, the connector maintains a number of additional columns for each table. If these columns are hidden, they can still be used in queries, but they do not show up in DESCRIBE <table-name> or SELECT *.

This property is optional; the default is true.

`redis.database-index`#

The Redis database to query.

This property is optional; the default is 0.

`redis.user`#

The username for Redis server.

This property is optional; the default is null.

`redis.password`#

The password for password-protected Redis server.

This property is optional; the default is null.

Internal columns#

For each defined table, the connector maintains the following columns:

Column name	Type	Description
`_key`	VARCHAR	Redis key.
`_value`	VARCHAR	Redis value corresponding to the key.
`_key_length`	BIGINT	Number of bytes in the key.
`_value_length`	BIGINT	Number of bytes in the value.
`_key_corrupt`	BOOLEAN	True if the decoder could not decode the key for this row. When true, data columns mapped from the key should be treated as invalid.
`_value_corrupt`	BOOLEAN	True if the decoder could not decode the message for this row. When true, data columns mapped from the value should be treated as invalid.

For tables without a table definition file, the _key_corrupt and _value_corrupt columns are false.

Table definition files#

With the Redis connector it is possible to further reduce Redis key/value pairs into granular cells, provided the key/value string follows a particular format. This process defines new columns that can be further queried from Trino.

A table definition file consists of a JSON definition for a table. The name of the file can be arbitrary, but must end in .json.

{
    "tableName": ...,
    "schemaName": ...,
    "key": {
        "dataFormat": ...,
        "fields": [
            ...
        ]
    },
    "value": {
        "dataFormat": ...,
        "fields": [
            ...
       ]
    }
}

Field	Required	Type	Description
`tableName`	required	string	Trino table name defined by this file.
`schemaName`	optional	string	Schema which will contain the table. If omitted, the default schema name is used.
`key`	optional	JSON object	Field definitions for data columns mapped to the value key.
`value`	optional	JSON object	Field definitions for data columns mapped to the value itself.

Please refer to the Kafka connector page for the description of the dataFormat as well as various available decoders.

In addition to the above Kafka types, the Redis connector supports hash type for the value field which represent data stored in the Redis hash.

{
    "tableName": ...,
    "schemaName": ...,
    "value": {
        "dataFormat": "hash",
        "fields": [
            ...
       ]
    }
}

SQL support#

The connector provides globally available and read operation statements to access data and metadata in Redis.

Performance#

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

Pushdown#

Примечание

Коннектор осуществляет pushdown для улучшения производительности запросов. Вместо с тем, коннектор не будет делать pushdown конкретной операции, если это может привести к некорректным результатам. Таким образом коннектор предпочитает корректность производительности. В некоторых случаях коннекторы могут предоставлять дополнительные параметры конфигурации, которые разрешают pushdown небезопасных операций, но только при явном указании соответствующего параметра пользователем.

Predicate pushdown support#

The connector supports pushdown of keys of string type only, the zset type is not supported. Key pushdown is not supported when multiple key fields are defined in the table definition file.

The connector supports pushdown of equality predicates, such as IN or =. Inequality predicates, such as !=, and range predicates, such as >, <, or BETWEEN are not pushed down.

In the following example, the predicate of the first query is not pushed down since > is a range predicate. The other queries are pushed down:

-- Not pushed down
SELECT * FROM nation WHERE redis_key > 'CANADA';
-- Pushed down
SELECT * FROM nation WHERE redis_key = 'CANADA';
SELECT * FROM nation WHERE redis_key IN ('CANADA', 'POLAND');

Redis коннектор#

Требования#

Конфигурация#

Multiple Redis servers#

Configuration properties#

redis.table-names#

redis.default-schema#

redis.nodes#

redis.scan-count#

redis.max-keys-per-fetch#

redis.key-prefix-schema-table#

redis.key-delimiter#

redis.table-description-dir#

redis.table-description-cache-ttl#

redis.hide-internal-columns#

redis.database-index#

redis.user#

redis.password#