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

[Hans Dingemans]

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.


>  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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