Events can have the attributes (a.k.a. attribs, properties or props) listed below. Some attributes are only available in certain input. For example, Warning_count is only available in tcpdump input. Even then, an attribute is only available if it actually appeared in the input or could be calculated. Therefore, do not always assume that an attribute is available.

Versions of mk-query-digest after r3968 auto-detect and print almost all attribs that it discovers. Certain properties are ignored; see mk-query-digest's default value for --ignore-attributes.

Attribute Classes

There are four classes of attributes: internal, normal, SET and Percona-patch.

Internal attribs do not appear in the input (i.e. the slow log, tcpdump, or processlist) but are created by the event parsing module (i.e. SlowLogParser, MySQLProtocolParser, Processlist, MemcachedEvent). Internal attribs help accomplish various things inside the code. They are generally ignored by the user. Once exception is memcached attributes; see below.

Normal attribs do appear in the input; they are the ones with which you're most familiar: Query_time, Lock_time, etc. These attributes come from the event's header.

SET attribs also appear in the input but unlike normal attributes they do not appear in the event's header. Rather, they are attributes from SET statements. The statement SET insert_id=123; creates an insert_id attribute with value 123.

Percona-patch attribs are also appear in the input and the event's header but only if you're using a Percona-patched server or Percona binary.

Knowing these attributes can help you write fancy --filter subs for mk-query-digest or know which attributes to --select or --ignore-attributes.

memcached

As of roughly r4159, mk-query-digest can parse memcached data from a tcpdump (mk-query-digest --type memcached). Several memcached attributes come from the protocol, like cmd, key, val and res. These are generally not used by the user and so they're listed as internal attributes. But from these several normal attributes are created which begin with "Memc".

Internal attributes

Normal attributes

Common SET attributes

Percona-patch attributes

The most up-to-date documentation on the Percona patches should be found at http://www.percona.com/docs/wiki/patches:microslow_innodb, but we list them below in an abbreviated form.