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Redis

Redis is an open-source in-memory storage, used as a distributed, in-memory key–value database, cache and message broker, with optional durability.

The Redis Wrapper allows you to read data from Redis within your Postgres database.

Warning

Restoring a logical backup of a database with a materialized view using a foreign table can fail. For this reason, either do not use foreign tables in materialized views or use them in databases with physical backups enabled.

Supported Redis Data Types

All Redis value will be stored as text or jsonb column in Postgres, below are the supported Redis data types:

Redis Type Foreign Table Type (src_type)
List list
Set set
Hash hash
Sorted Set zset
Stream stream
Multiple List multi_list
Multiple Set multi_set
Multiple Hash multi_hash
Multiple Sorted Set multi_zset

See below for more descriptions for the Multiple * types and src_type foreign table option.

Preparation

Before you get started, make sure the wrappers extension is installed on your database:

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create extension if not exists wrappers with schema extensions;

and then create the foreign data wrapper:

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create foreign data wrapper redis_wrapper
  handler redis_fdw_handler
  validator redis_fdw_validator;

Secure your credentials (optional)

By default, Postgres stores FDW credentials inside pg_catalog.pg_foreign_server in plain text. Anyone with access to this table will be able to view these credentials. Wrappers is designed to work with Vault, which provides an additional level of security for storing credentials. We recommend using Vault to store your credentials.

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-- Save your Redis connection URL in Vault and retrieve the `key_id`
insert into vault.secrets (name, secret)
values (
  'redis_conn_url',
  'redis://username:password@127.0.0.1:6379/db'
)
returning key_id;

Connecting to Redis

We need to provide Postgres with the credentials to connect to Redis. We can do this using the create server command:

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create server redis_server
  foreign data wrapper redis_wrapper
  options (
    conn_url_id '<key_ID>' -- The Key ID from above.
  );

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create server redis_server
  foreign data wrapper redis_wrapper
  options (
    conn_url 'redis://username:password@127.0.0.1:6379/db'
  );

The connection URL format is:

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redis://[<username>][:<password>@]<hostname>[:port][/<db>]

Creating Foreign Tables

The Redis Wrapper supports data reads from Redis.

Integration Select Insert Update Delete Truncate
Redis ✅ ❌ ❌ ❌ ❌

For example:

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create foreign table redis_list (
  element text
)
  server redis_server
  options (
    src_type 'list',
    src_key 'my_list'
  );

The foreign table columns names and types must be fixed for each source type, as listed below:

src_type Column name Column type
list, set, zset element text
hash key text
value text
stream id text
items jsonb
multi_* key text
items jsonb

See below for the full list of src_type and descriptions.

Foreign table options

The full list of foreign table options are below:

  • src_type - Foreign table source type in Redis, required.

This can be one of below types,

Source type Description
list Single list
set Single set
hash Single hash
zset Single sorted set
stream Stream
multi_list Multiple lists, specified by src_key pattern
multi_set Multiple sets, specified by src_key pattern
multi_hash Multiple hashes, specified by src_key pattern
multi_zset Multiple sorted sets, specified by src_key pattern
  • src_key - Source object key in Redis, required.

This key can be a pattern for multi_* type of foreign table. For other types, this key must return exact one value. For example,

Source Type src_key examples
list, set, hash, zset, stream my_list, list:001, hash_foo, zset:1000 and etc.
multi_list, multi_set, multi_hash, multi_zset my_list:*, set:*, zset:* and etc.

Query Pushdown Support

This FDW doesn't supports pushdown.

Examples

Some examples on how to use Redis foreign tables.

Let's prepare some source data in Redis CLI first:

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127.0.0.1:6379> RPUSH list foo bar 42
127.0.0.1:6379> SADD set foo bar 42
127.0.0.1:6379> HSET hash foo bar baz qux
127.0.0.1:6379> ZADD zset 30 foo 20 bar 10 baz
127.0.0.1:6379> XADD stream * foo bar
127.0.0.1:6379> XADD stream * aa 42 bb 43

127.0.0.1:6379> RPUSH list:100 foo bar
127.0.0.1:6379> RPUSH list:200 baz

127.0.0.1:6379> SADD set:100 foo
127.0.0.1:6379> SADD set:200 bar

127.0.0.1:6379> HSET hash:100 foo bar
127.0.0.1:6379> HSET hash:200 baz qux

127.0.0.1:6379> ZADD zset:100 10 foo 20 bar
127.0.0.1:6379> ZADD zset:200 40 baz 30 qux

Basic example

This example will create foreign tables inside your Postgres database and query their data:

  • List
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create foreign table redis_list (
  element text
)
server redis_server
options (
  src_type 'list',
  src_key 'list'
);

select * from redis_list;

Query result:

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 element
---------
 foo
 bar
 42
(3 rows)
  • Set
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create foreign table redis_set (
  element text
)
server redis_server
options (
  src_type 'set',
  src_key 'set'
);

select * from redis_set;

Query result:

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 element
---------
 42
 foo
 bar
(3 rows)
  • Hash
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create foreign table redis_hash (
  key text,
  value text
)
server redis_server
options (
  src_type 'hash',
  src_key 'hash'
);

select * from redis_hash;

Query result:

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 key | value
-----+-------
 foo | bar
 baz | qux
(2 rows)
  • Sorted set
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create foreign table redis_zset (
  element text
)
server redis_server
options (
  src_type 'zset',
  src_key 'zset'
);

select * from redis_zset;

Query result:

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 element
---------
 baz
 bar
 foo
(3 rows)
  • Stream
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create foreign table redis_stream (
  id text,
  items jsonb
)
server redis_server
options (
  src_type 'stream',
  src_key 'stream'
);

select * from redis_stream;

Query result:

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       id        |          items
-----------------+--------------------------
 1704343825989-0 | {"foo": "bar"}
 1704343829799-0 | {"aa": "42", "bb": "43"}
(2 rows)

Query multiple objects example

This example will create several foreign tables using pattern in key and query multiple objects from Redis:

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create foreign table redis_multi_lists (
  key text,
  items jsonb
)
  server redis_server
  options (
    src_type 'multi_list',
    src_key 'list:*'
  );

select * from redis_multi_lists;

Query result:

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   key    |     items
----------+----------------
 list:100 | ["foo", "bar"]
 list:200 | ["baz"]
(2 rows)
  • Set
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create foreign table redis_multi_sets (
  key text,
  items jsonb
)
  server redis_server
  options (
    src_type 'multi_set',
    src_key 'set:*'
  );

select * from redis_multi_sets;

Query result:

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   key   |  items
---------+---------
 set:100 | ["foo"]
 set:200 | ["bar"]
(2 rows)
  • Hash
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create foreign table redis_multi_hashes (
  key text,
  items jsonb
)
  server redis_server
  options (
    src_type 'multi_hash',
    src_key 'hash:*'
  );

select * from redis_multi_hashes;

Query result:

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   key    |     items
----------+----------------
 hash:200 | {"baz": "qux"}
 hash:100 | {"foo": "bar"}
(2 rows)
  • Sorted set
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create foreign table redis_multi_zsets (
  key text,
  items jsonb
)
  server redis_server
  options (
    src_type 'multi_zset',
    src_key 'zset:*'
  );

select * from redis_multi_zsets;

Query result:

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   key    |     items
----------+----------------
 zset:200 | ["qux", "baz"]
 zset:100 | ["foo", "bar"]
(2 rows)