The DTrace probes in the MySQL server are designed to provide
information about the execution of queries within MySQL and the
different areas of the system being utilized during that process.
The organization and triggering of the probes means that the
execution of an entire query can be monitored with one level of
query-done) but by monitoring other probes you
can get successively more detailed information about the execution
of the query in terms of the locks used, sort methods and even
row-by-row and storage-engine level execution information.
The DTrace probes are organized so that you can follow the entire query process, from the point of connection from a client, through the query execution, row-level operations, and back out again. You can think of the probes as being fired within a specific sequence during a typical client connect/execute/disconnect sequence, as shown in the following figure.
Global information is provided in the arguments to the DTrace
probes at various levels. Global information, that is, the
connection ID and user/host and where relevant the query string,
is provided at key levels (
query-exec-start). As you go deeper into
the probes, it is assumed either you are only interested in the
individual executions (row-level probes provide information on the
database and table name only), or that you combine the row-level
probes with the notional parent probes to provide the information
about a specific query. Examples of this are given as the format
and arguments of each probe are provided.
MySQL includes support for DTrace probes on these platforms:
Solaris 10 Update 5 (Solaris 5/08) on SPARC, x86 and x86_64 platforms
OS X 10.4 and higher
Oracle Linux 6 and higher with UEK kernel (as of MySQL 5.6.20)
If a non-Solaris platform includes DTrace support, building mysqld on that platform includes DTrace support.