bug#43791: cuirass: Search queries are too slow.

[Mathieu Othacehe <othacehe@gnu.org>]

Hello,

Search queries can take a long time to complete.

This query took 658.67 seconds to complete:

--8<---------------cut here---------------start------------->8---
SELECT * FROM ( SELECT Builds.rowid, Builds.timestamp, Builds.starttime, Builds.stoptime, Builds.log, Builds.status, Builds.job_name, Builds.system, Builds.nix_name, Specifications.name FROM Builds INNER JOIN Evaluations ON Builds.evaluation = Evaluations.id INNER JOIN Specifications ON Evaluations.specification = Specifications.name WHERE (Builds.nix_name LIKE '%hurd-barebones.qcow2%') AND (0 IS NULL OR (Builds.status = 0)) AND ('guix-master' IS NULL OR (Specifications.name = 'guix-master')) AND ('x86_64-linux' IS NULL OR (Builds.system = 'x86_64-linux')) AND (NULL IS NULL OR (NULL < Builds.rowid)) AND (NULL IS NULL OR (NULL > Builds.rowid)) ORDER BY CASE WHEN NULL IS NULL THEN Builds.rowid ELSE -Builds.rowid END DESC LIMIT 1) ORDER BY rowid DESC 658.67
--8<---------------cut here---------------end--------------->8---

and this one:

--8<---------------cut here---------------start------------->8---
SELECT MIN(Builds.rowid) FROM Builds INNER JOIN Evaluations ON Builds.evaluation = Evaluations.id INNER JOIN Specifications ON Evaluations.specification = Specifications.name WHERE (Builds.nix_name LIKE '%ganeti%') AND (NULL IS NULL OR (Builds.status = NULL)) AND (NULL IS NULL OR (Specifications.name = NULL)) AND (NULL IS NULL OR (Builds.system = NULL)) 146.70
--8<---------------cut here---------------end--------------->8---

took 146.70 seconds.

The naive solution of adding an index on nix_name column does not work
as it is still ignored for some reason.

According to https://www.sqlite.org/optoverview.html, starting the LIKE
search pattern with '%' prevent the index use.

However, searching for 'hurd-barebones.qcow2%' also skips the index.

Thanks,

Mathieu