maria-developers team mailing list archive

[Jeremy Zawodny <Jeremy@xxxxxxxxxxx>]

Agreed.  Make it easy to grep and don't pretend the log is an XML file. :-)

Jeremy


On Sat, Oct 19, 2013 at 8:26 AM, Eric Bergen <eric.bergen@xxxxxxxxx> wrote:

> I don't understand why you need both the <explain> xml style tag and
> the double # to denote an explain entry. I would prefer to see each
> line prefixed with # explain: to make it similar to the other info
> lines above and get rid of the <explain>.
>
> By prefixing each line with # explain: it makes grepping explain plans
> easier than looking for a start and end tag on different lines.
>
> On Fri, Oct 18, 2013 at 4:59 PM, Sergei Golubchik <serg@xxxxxxxxxxx>
> wrote:
> > Hi, Sergei!
> >
> > On Oct 18, Sergei Petrunia wrote:
> >> Hello,
> >>
> >> After recent changes in the [SHOW] EXPLAIN architecture in MariaDB, it
> became
> >> really easy to add an option to print EXPLAIN(*) output into the slow
> query log,
> >> so I went ahead and implemented it.
> >>
> >> @@log_slow_verbosity has got a 'explain' flag, and if it is on, the
> slow query
> >> log entries look like this:
> >>
> >> # Time: 131017 21:26:02
> >> # User@Host: root[root] @ localhost []
> >> # Thread_id: 2  Schema: dbt3sf1  QC_hit: No
> >> # Query_time: 5.535819  Lock_time: 0.000350  Rows_sent: 1
>  Rows_examined: 65633
> >> ## <explain>
> >> ##   id select_type     table   type    possible_keys   key     key_len
> ref     rows    Extra
> >> ##   1  SIMPLE  nation  ref     PRIMARY,n_name  n_name  26      const
> 1       Using where; Using index
> >> ##   1  SIMPLE  customer        ref     PRIMARY,i_c_nationkey
> i_c_nationkey   5       dbt3sf1.nation.n_nationkey      25124   Using index
> >> ##   1  SIMPLE  orders  ref     i_o_custkey     i_o_custkey     5
> dbt3sf1.customer.c_custkey      7       Using index
> >> ## </explain>
> >> SET timestamp=1382030762;
> >> select count(*) from customer, orders, nation where c_custkey=o_custkey
> and c_nationkey=n_nationkey and n_name='GERMANY';
> >>
> >> It seems, pt-slow-query-log has no problem parsing this.
> >>
> >> Open questions:
> >>
> >> - Is this syntax OK?
> >
> > Yes, assuming you use tabs as column separators, not spaces.
> >
> >> - Currently, some statements (like SHOW KEYS) print a dumb explain that
> >> shows that full table scan is used. There is a suggestion to not print
> >> EXPLAIN for any SHOW statements. Is this ok?
> >
> > Yes. If users will complain we can always change it back later.
> >
> > Regards,
> > Sergei
> >
> > _______________________________________________
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>
>
> --
> Eric Bergen
> eric.bergen@xxxxxxxxx
> http://www.ebergen.net
>
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