[mythtv] Ticket #13517: Reducing memory usage by mythfilldatabase to 1/6 of original usage

David Engel david at istwok.net
Sun Feb 16 21:13:49 UTC 2020


On Sun, Feb 16, 2020 at 03:33:21PM -0500, Hans Dingemans wrote:
> On Sun, Feb 16, 2020 at 9:12 AM MythTV <noreply at mythtv.org> wrote:
> 
> > #13517: Reducing memory usage by mythfilldatabase to 1/6 of original usage
> > ---------------------------------------+-------------------------------
> >  Reporter:  Hans Dingemans             |          Owner:  Peter Bennett
> >      Type:  Patch - Feature            |         Status:  assigned
> >  Priority:  minor                      |      Milestone:  needs_triage
> > Component:  MythTV - Mythfilldatabase  |        Version:  Master Head
> >  Severity:  medium                     |     Resolution:
> >  Keywords:                             |  Ticket locked:  0
> > ---------------------------------------+-------------------------------
> >
> > Comment (by Peter Bennett):
> >
> >  Gary - thank you for your valuable input.
> >
> >  Hans -
> >  Regarding using database rollback - MythTV uses autocommit throughout, so
> >  I don't think that is an option.
> >
> That won't be a problem; from the MYSQL manual:
> 
> To disable autocommit mode implicitly for a single series of statements,
> use the START TRANSACTION statement:
> 
> With START TRANSACTION, autocommit remains *disabled until you end the
> transaction with COMMIT or ROLLBACK.* The autocommit mode then reverts to
> its previous state.

Mike Dean is our primary, database expert.  I'll defer to him when/if
he chimes in.  However, my understanding is that MythTV only
officially supports tables using the MyISAM, storage engine and that
that storage engine doesn't support transactions.

David

> >  Does the system complete parsing before updating the database?
> 
> Yes.
> 
> > If so it
> >  should be easy to reject the whole run if there is an error.
> >
> Yes this patch it does that already; however, I'll test a few of the cases
> Gary described, and come back to you, because I am not sure if the XML
> syntax checking is as accurate with QXmlStreamReader  as it is with
> XDomDocument; I guess only the library maintainers know for sure :-)
> 
> >
> >  When updating the database does it first delete old data? If so it would
> >  be dangerous to accept a half complete run because the program data may be
> >  deleted and not replaced.
> >
> > --
> > Ticket URL: <https://code.mythtv.org/trac/ticket/13517#comment:11>
> > MythTV <http://www.mythtv.org>
> > MythTV Media Center
> >
> 
> Greetings, Hans.

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-- 
David Engel
david at istwok.net


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