[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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