View and configure runtime parameters

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What are runtime parameters?

Runtime parameters are variables that can be set at runtime to configure the behavior of RisingWave. They are also known as session variables.

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How to view runtime parameters?

You can use the SHOW ALL command to view the runtime parameters, their current settings, and some notes about these parameters.

SHOW ALL;

For example, you may see a table similar to this:

          Name                  |     Setting     |        Description
--------------------------------+-----------------+--------------------------------------
 rw_implicit_flush              | false           | If `RW_IMPLICIT_FLUSH` is on, then every INSERT/UPDATE/DELETE statement will block until the entire dataflow is refreshed.
 create_compaction_group_for_mv | false           | If `CREATE_COMPACTION_GROUP_FOR_MV` is on, dedicated compaction groups will be created in MV creation.
 query_mode                     | auto            | A temporary config variable to force query running in either local or distributed mode. If the value is auto, the system will decide for you automatically.
 ...

Below is the detailed information about the parameters you may see after using the SHOW ALL command:

If you just want to view a specific parameter’s value, you can also use the SHOW command.

SHOW parameter_name;

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How to configure runtime parameters?

You can use SET command or the set_config() function to change the setting of a runtime parameter.

The syntax of the SET command is:

SET parameter_name { TO | = } { value | 'value' | DEFAULT};

Where parameter_name is the name of the parameter, and value or 'value' is the new value of the parameter. DEFAULT can be written to specify resetting the parameter to its default value.

For details about the set_config() function, see System administration functions, and for details about the SET command, see SET.

You can also use the ALTER SYSTEM SET command to set a system-wide default value for a runtime parameter. This configuration will then be applied to every new session.

ALTER SYSTEM SET session_param_name TO session_param_value;