20.15. Parameter Limits
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## 20.15. Parameter Limits

Some roles (users or groups) can be restricted in setting the configuration parameters. The administrator can define particular restricions in the `guc_limits.json` file and put it into the data directory.

The file is a JSON array where each element represents a single limit. Multiple limits can be assigned to a single variable. The following limit attributes are required regardless the parameter data type:

- `var_name`

  Name of the variable (parameter) whose values should be limited.

- `roles`

  List of roles (users, groups) who cannot change the variable value beyond the limit.

The other attributes are only applicable to parameters of specific data types.

### 20.15.1. Boolean Limits

- `value`

  The allowed value of the parameter.

### 20.15.2. String Limits

- `value`

  The allowed value of the parameter.

- `allow_empty`

  Can the parameter be set to empty string? The default value is `true`.

### 20.15.3. Integer Limits

- `min`

  Minimum value of the parameter.

- `max`

  Maximum value of the parameter.

### 20.15.4. Numeric Limits

- `min`

  Minimum value of the parameter.

- `include_min`

  Is the minimum value allowed itself? The default value is `false`.

- `max`

  Maximum value of the parameter.

- `include_max`

  Is the maximum value allowed itself? The default value is `false`.

### 20.15.5. Enumerated Limits

- `values`

  The list of values the parameter can be assigned.

### 20.15.6. Example configuration

The following sample file shows how limits can be imposed on configuration parameters of different data types.

    [
        {
            "var_name" : "enable_seqscan",
            "value" : true,
            "roles" : ["app1"]
        },

        {
            "var_name" : "work_mem",
            "min" : 1024,
            "max" : 2048,
            "roles" : ["monitor"]
        },

        {
            "var_name" : "work_mem",
            "min" : 1024,
            "max" : "16MB",
            "roles" : ["admin"]
        },

        {
            "var_name" : "max_parallel_workers",
            "max" : 10,
            "roles" : ["app1", "app2"]
        },

        {
            "var_name" : "default_tablespace",
            "value" : "tbsp_app1",
            "roles" : ["app1"]
        },

        {
            "var_name" : "client_min_messages",
            "values" : ["log", "info", "notice", "warning", "error"],
            "roles" : ["app1", "app2"]
        }
    ]

You can enforce rereading of the `guc_limits.json` file in the same way as you would do for `postgresql.conf`: by running `pg_ctl reload` from the command line or by calling the SQL function `pg_reload_conf()`.

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