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Keys and IDs

Redis keys are named by the application. JDBC generated keys are not available, but a Mapper can assign a command's returned number to an object property.

Key Strategies​

Redis does not use entity KeyType strategies to generate table primary keys. Supply command keys explicitly; use INCR before writing or return an ID from a script as shown below.

Key Strategies in Mapper Files​

The caller can supply command keys directly. To fill an ID, use selectKey to execute INCR or read an existing ID, or set generatedKeySource="resultSet" to receive a script result. Redis does not provide JDBC generated keys or relational auto-increment columns.

Allocate an ID before writing​

Use INCR to allocate a number, then use it as a Hash field. The record has writable Long id and String counter, key, and value properties.

@Insert("HSET #{key} #{id} #{value}")
@SelectKeySql(value = "INCR #{counter}", keyProperty = "id", order = Order.Before)
int save(Record record);

With counter="user:sequence" and key="users", the generated number becomes both record.id and a field in the users Hash. These are two commands; a failed write does not return the allocated number.

Assign a script result to a property​

To allocate the number and write the value in one command, use EVAL. Select GeneratedKeySource.ResultSet and its VALUE column:

@Insert(value = "EVAL \"local id=redis.call('INCR',KEYS[1]); "
        + "redis.call('HSET',KEYS[2],id,ARGV[1]); return id\" "
        + "2 #{counter} #{key} #{value}",
        useGeneratedKeys = true, generatedKeySource = GeneratedKeySource.ResultSet,
        keyProperty = "id", keyColumn = "VALUE")
int save(Record record);

After the call, read record.getId(). In a Mapper file, put the same command in <insert> with useGeneratedKeys="true" generatedKeySource="resultSet" keyProperty="id" keyColumn="VALUE".

Only the command-result source is supported here. Omitting generatedKeySource requests JDBC generated keys and does not perform this assignment. EVAL does not provide rollback after a script error.

General configuration: Generated keys.