# Query Log All Filter

## Overview

The Query Log All (QLA) filter is a filter module for MariaDB MaxScale that is able to log all query content on a per client session basis. Logs are written in a csv format file that lists the time submitted and the SQL statement text.

## Configuration

The configuration block for the QLA filter requires the minimal filter options in it's section within the maxscale.cnf file, stored in /etc/maxscale.cnf.
```
[MyLogFilter]
type=filter
module=qlafilter

[MyService]
type=service
router=readconnrouter
servers=server1
user=myuser
passwd=mypasswd
filters=MyLogFilter
```

## Filter Options

The QLA filter accepts the following options.

|Option |Description |
|----------|--------------------------------------------|
|ignorecase|Use case-insensitive matching |
|case |Use case-sensitive matching |
|extended |Use extended regular expression syntax (ERE)|

To use multiple filter options, list them in a comma-separated list.

```
options=case,extended
```

**Note**: older the version of the QLA filter in 0.7 of MariaDB MaxScale used the `options`
to define the location of the log files. This functionality is not supported
anymore and the `filebase` parameter should be used instead.

## Filter Parameters

The QLA filter has one mandatory parameter, `filebase`, and a number of optional parameters. These were introduced in the 1.0 release of MariaDB MaxScale.

### Filebase

The basename of the output file created for each session. A session index is added to the filename for each file written. This is a mandatory parameter.

```
filebase=/tmp/SqlQueryLog
```

The filebase may also be set as the filter, the mechanism to set the filebase via the filter option is superseded by the parameter. If both are set the parameter setting will be used and the filter option ignored.

### Match

An optional parameter that can be used to limit the queries that will be logged by the QLA filter. The parameter value is a regular expression that is used to match against the SQL text. Only SQL statements that matches the text passed as the value of this parameter will be logged.

```
match=select.*from.*customer.*where
```

All regular expressions are evaluated with the option to ignore the case of the text, therefore a match option of select will match both select, SELECT and any form of the word with upper or lowercase characters.

### Exclude

An optional parameter that can be used to limit the queries that will be logged by the QLA filter. The parameter value is a regular expression that is used to match against the SQL text. SQL statements that match the text passed as the value of this parameter will be excluded from the log output.

```
exclude=where
```

All regular expressions are evaluated with the option to ignore the case of the text, therefore an exclude option of select will exclude statements that contain both select, SELECT or any form of the word with upper or lowercase characters.

### Source

The optional source parameter defines an address that is used to match against the address from which the client connection to MariaDB MaxScale originates. Only sessions that originate from this address will be logged.

```
source=127.0.0.1
```

### User

The optional user parameter defines a user name that is used to match against the user from which the client connection to MariaDB MaxScale originates. Only sessions that are connected using this username are logged.

```
user=john
```

## Examples

### Example 1 - Query without primary key

Imagine you have observed an issue with a particular table and you want to determine if there are queries that are accessing that table but not using the primary key of the table. Let's assume the table name is PRODUCTS and the primary key is called PRODUCT_ID. Add a filter with the following definition:

```
[ProductsSelectLogger]
type=filter
module=qlafilter
match=SELECT.*from.*PRODUCTS .*
exclude=WHERE.*PRODUCT_ID.*
filebase=/var/logs/qla/SelectProducts

[Product Service]
type=service
router=readconnrouter
servers=server1
user=myuser
passwd=mypasswd
filters=ProductsSelectLogger
```

The result of then putting this filter into the service used by the application would be a log file of all select queries that mentioned the table but did not mention the PRODUCT_ID primary key in the predicates for the query.
Executing `SELECT * FROM PRODUCTS` would log the following into `/var/logs/qla/SelectProducts`:
```
07:12:56.324 7/01/2016, SELECT * FROM PRODUCTS
```