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From: Steven Rostedt <rostedt@goodmis.org>
To: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Tom Zanussi <zanussi@kernel.org>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	linux-rt-users <linux-rt-users@vger.kernel.org>,
	Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 17/17] libtracefs: Add man page for tracefs_sql()
Date: Sun, 1 Aug 2021 18:29:16 -0400	[thread overview]
Message-ID: <20210801182916.689a84a8@rorschach.local.home> (raw)
In-Reply-To: <YQakDYRnId+bK+ue@lx-t490>

On Sun, 1 Aug 2021 15:39:25 +0200
"Ahmed S. Darwish" <a.darwish@linutronix.de> wrote:

> On Fri, Jul 30, 2021, Steven Rostedt wrote:
> > +
> > +The SQL format is as follows:
> > +
> > +*SELECT* <fields> FROM <start-event> JOIN <end-event> ON <matching-fields> WHERE <filter>
> > +
> > +Note, although the examples show the SQL commands in uppercase, they are not required to
> > +be so. That is, you can use "SELECT" or "select" or "sElEct".
> > +  
> 
> Maybe it would be helpful to mention that, unlike normal SELECT queries,
> the JOIN and ON parts above are _not_ optional?
> 
> That is, generic "one event source" queries:
> 
>   SELECT common_pid,msr,val FROM write_msr WHERE msr=72
> 
> are not supported. (I wish they were though ;-))

Actually, the sql parser should support it, but it will fail on the
creation of events. That's because I started trying to make this create
normal histograms. The problem is, that it can't really do a 1 to 1 on
histograms and selects, so I gave up. But perhaps for the subset it can
create, maybe I can still have it do so. That may require changing the
API slightly. 

I'm not a big SQL person, so I don't know all the magic and I have no
idea how to add the "values" part of the hist trigger.

I could use SQL CAST to let people redefine the types that histograms
allow, like:

   SELECT CAST(common_pid AS execname), CAST(id AS syscall) FROM sys_enter

and have that produce:

 echo 'hist:keys=common_pid.execname,id.syscall' > events/raw_syscalls/sys_enter/trigger

Any ideas for the syntax to get values? Or do people care about the
value parameter any more than just "hitcount"? I don't think I have
ever used it for anything.

> 
> BTW, thanks a lot for this work. It will finally make synthetic events
> usable!
> 

Thanks! It's also something to make it easier for me to use. And
hopefully, allow for even more complex synthetic events.

-- Steve

  reply	other threads:[~2021-08-01 22:29 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 22:18 [PATCH 00/17] libtracefs: Introducing tracefs_sql() to create synthetice events with an SQL line Steven Rostedt
2021-07-30 22:18 ` [PATCH 01/17] libtracefs: Added new API tracefs_sql() Steven Rostedt
2021-08-01  6:32   ` Ahmed S. Darwish
2021-08-01 22:10     ` Steven Rostedt
2021-08-02 23:45   ` Namhyung Kim
2021-08-03  2:49     ` Steven Rostedt
2021-07-30 22:18 ` [PATCH 02/17] tracefs: Add unit tests for tracefs_sql() Steven Rostedt
2021-07-30 22:18 ` [PATCH 03/17] libtracefs: Add comparing start and end fields in tracefs_sql() Steven Rostedt
2021-07-30 22:18 ` [PATCH 04/17] libtracefs: Add unit test to test tracefs_sql() compare Steven Rostedt
2021-07-30 22:18 ` [PATCH 05/17] libtracefs: Add filtering for start and end events in tracefs_sql() Steven Rostedt
2021-07-30 22:18 ` [PATCH 06/17] libtracefs: Add unit test to test tracefs_sql() where clause Steven Rostedt
2021-07-30 22:18 ` [PATCH 07/17] libtracefs: Make sqlhist parser reentrant Steven Rostedt
2021-07-30 22:18 ` [PATCH 08/17] libtracefs: Make parser unique to libtracefs Steven Rostedt
2021-07-30 22:18 ` [PATCH 09/17] libtracefs: Add line number and index to expr structure Steven Rostedt
2021-07-30 22:18 ` [PATCH 10/17] libtracefs: Add a parse_error() helper function to record errors Steven Rostedt
2021-07-30 22:18 ` [PATCH 11/17] libtracefs: Add error message when match fields are not FROM and JOIN events Steven Rostedt
2021-07-30 22:18 ` [PATCH 12/17] libtracefs: Add error message when match or init fails from bad events Steven Rostedt
2021-07-30 22:18 ` [PATCH 13/17] libtracefs; Add error message for bad selections to SQL sequence Steven Rostedt
2021-07-30 22:18 ` [PATCH 14/17] libtracefs: Add error message when compare fields fail Steven Rostedt
2021-07-30 22:18 ` [PATCH 15/17] libtracefs: Add error message for grouping events in SQL filter Steven Rostedt
2021-07-30 22:18 ` [PATCH 16/17] libtracefs: Add error message for bad filters in SQL statement Steven Rostedt
2021-07-30 22:18 ` [PATCH 17/17] libtracefs: Add man page for tracefs_sql() Steven Rostedt
2021-08-01 13:39   ` Ahmed S. Darwish
2021-08-01 22:29     ` Steven Rostedt [this message]
2021-08-04 12:27       ` Ahmed S. Darwish
2021-07-30 22:31 ` [PATCH 00/17] libtracefs: Introducing tracefs_sql() to create synthetice events with an SQL line Steven Rostedt

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