Re: [Outreachy] - Guix Data Service - Set a more informative page title

[Christopher Baines <mail@cbaines.net>]

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Canan Talayhan <canan.t.talayhan@gmail.com> writes:

> It seems after testing lots of pages this one escaped me since I only
> tested the working case.
>
> Please find the quick fix in the link below.
> https://pastebin.ubuntu.com/p/s7tWyPHZ8F/

Great, that fixes the issue with the revision comparison page.

> I'm looking forward to making another contribution. Could you please
> review it as soon as possible?

I've gone ahead and merged this. I made some changes to the indentation,
I've generally just left that to Emacs, so that's effectively the
indentation style currently. I also tweaked the wording in the commit
message.

As for what to do next, it would be good to start looking at some stuff
that's more related to the project topic.

Part of the revision processing that I believe is quite slow and
hopefully can be improved is populating the package_metadata table. The
relevant lines in the job output look something like this:

  debug: Starting querying the temp_package_metadata
  debug: Finished querying the temp_package_metadata, took 1902 seconds

That output comes from the with-time-logging bit around here [1]. It's a
single query, generated by temp-table-select-query which is taking
around 30 minutes it seems, and I'd hope either the query can be made
faster, or some other faster way of doing what needs doing here can be
found.

1: https://git.savannah.gnu.org/cgit/guix/data-service.git/tree/guix-data-service/model/utils.scm#n333

insert-missing-data-and-return-all-ids is used in a few places, but this
specific issue arises when called from here [2].

2: https://git.savannah.gnu.org/cgit/guix/data-service.git/tree/guix-data-service/model/package-metadata.scm#n373

Making inserting package metadata faster is the overall goal, but I'd
suggest first just trying to reproduce the slow query outside of the
revision processing process. That way you'll be able to look at what the
query is doing and quickly test changes.

The approach I'd recommend is, make yourself a realistic
temp_package_metadata table by populating it with all the
package_metadata entries for a single revision already in your local
database. Then construct and try the slow query, and see how long it
takes, and look at the query plan (run the query with EXPLAIN at the
start).

Do let me know if you have any questions or get stuck, I'll hopefully be
around on IRC, and if I don't respond within a few minutes there, just
email me.

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