Vertica supports a wide variety of configuration parameters that affect many facets of database behavior. These parameters can be set with the appropriate ALTER statements at one or more levels, listed here in descending order of precedence:

1. User (ALTER USER)

2. Session (ALTER SESSION)

3. Node (ALTER NODE)

4. Database (ALTER DATABASE)

You can query system table CONFIGURATION_PARAMETERS to obtain the current settings for all user-accessible parameters. For example, the following query obtains settings for partitioning parameters: their current and default values, which levels they can be set at, and whether changes require a database restart to take effect:

=> SELECT parameter_name, current_value, default_value, allowed_levels, change_requires_restart
      FROM configuration_parameters  WHERE parameter_name ILIKE '%partitioncount%';
    parameter_name    | current_value | default_value | allowed_levels | change_requires_restart
----------------------+---------------+---------------+----------------+-------------------------
 MaxPartitionCount    | 1024          | 1024          | NODE, DATABASE | f
 ActivePartitionCount | 1             | 1             | NODE, DATABASE | f
(2 rows)

For details about individual configuration parameters grouped by category, see Configuration parameters.

Setting and clearing configuration parameters

You change specific configuration parameters with the appropriate ALTER statements; the same statements also let you reset configuration parameters to their default values. For example, the following ALTER statements change ActivePartitionCount at the database level from 1 to 2 , and DisablePartitionCount at the session level from 0 to 1:

=> ALTER DATABASE DEFAULT SET ActivePartitionCount = 2;
ALTER DATABASE
=> ALTER SESSION SET DisableAutopartition = 1;
ALTER SESSION
=> SELECT parameter_name, current_value, default_value FROM configuration_parameters
      WHERE parameter_name IN ('ActivePartitionCount', 'DisableAutopartition');
    parameter_name    | current_value | default_value
----------------------+---------------+---------------
 ActivePartitionCount | 2             | 1
 DisableAutopartition | 1             | 0
(2 rows)

You can later reset the same configuration parameters to their default values:

=> ALTER DATABASE DEFAULT CLEAR ActivePartitionCount;
ALTER DATABASE
=> ALTER SESSION CLEAR DisableAutopartition;
ALTER DATABASE
=> SELECT parameter_name, current_value, default_value FROM configuration_parameters
      WHERE parameter_name IN ('ActivePartitionCount', 'DisableAutopartition');
    parameter_name    | current_value | default_value
----------------------+---------------+---------------
 DisableAutopartition | 0             | 0
 ActivePartitionCount | 1             | 1
(2 rows)