> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/maxscale/reference/maxscale-filters/maxscale-maxrows-filter.md).

# MaxScale Maxrows Filter

Limit the size of result sets returned to clients. This filter prevents excessive resource consumption by truncating results that exceed a configured row count.

## Overview

The Maxrows filter is capable of restricting the amount of rows that a SELECT, a prepared statement or stored procedure could return to the client application.

If a resultset from a backend server has more rows than the configured limit or the resultset size exceeds the configured size, an empty result will be sent to the client.

## Configuration

The Maxrows filter is easy to configure and to add to any existing service.

```
[MaxRows]
type=filter
module=maxrows

[MaxRows-Routing-Service]
type=service
...
filters=MaxRows
```

## Settings

The Maxrows filter has no mandatory parameters. Optional parameters are:

### `max_resultset_rows`

* Type: number
* Mandatory: No
* Dynamic: Yes
* Default: (no limit)
* Description: Specifies the maximum number of rows allowed in a result set returned to the client.

Specifies the maximum number of rows a resultset can have in order to be returned to the user.

If a resultset is larger than this an empty result will be sent instead.

```
max_resultset_rows=1000
```

### `max_resultset_size`

* Type: [size](/docs/maxscale/maxscale-management/deployment/installation-and-configuration/maxscale-configuration-guide.md#sizes)
* Mandatory: No
* Dynamic: Yes
* Default: `64Ki`
* Description: Restricts the size of a resultset that can be returned to the client; larger resultsets are replaced with an empty result.

Specifies the maximum size a resultset can have in order to be sent to the client. A resultset larger than this, will not be sent: an empty resultset will be sent instead.

```
max_resultset_size=128Ki
```

### `max_resultset_return`

* Type: [enum](/docs/maxscale/maxscale-management/deployment/installation-and-configuration/maxscale-configuration-guide.md#enumerations)
* Mandatory: No
* Dynamic: Yes
* Values: `empty`, `error`, `ok`
* Default: `empty`
* Description: Regulates the response that is sent to the client when the limitations defined by the results are exceeded.

Specifies what the filter sends to the client when the rows or size limit is hit, possible values:

* an empty result set
* an error packet with input SQL
* an OK packet

Example output with ERR packet:

```
MariaDB [(test)]> select * from test.t4;
ERROR 1415 (0A000): Row limit/size exceeded for query: select * from test.t4
```

### `debug`

* Type: number
* Mandatory: No
* Dynamic: Yes
* Default: `0`
* Description: Manages the level of debug logging for the MaxRows filter.

An integer value, using which the level of debug logging made by the Maxrows filter can be controlled. The value is actually a bitfield with different bits denoting different logging.

* `0` (`0b00000`) No logging is made.
* `1` (`0b00001`) A decision to handle data form server is logged.
* `2` (`0b00010`) Reached max\_resultset\_rows or max\_resultset\_size is logged.

To log everything, give `debug` a value of `3`.

```
debug=2
```

## Example Configuration

Here is an example of filter configuration where the maximum number of returned rows is 10000 and maximum allowed resultset size is 256KB

```
[MaxRows]
type=filter
module=maxrows
max_resultset_rows=10000
max_resultset_size=256000
```

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