Drop the unused id_country index on address when upgrading

[boo-code]

Companion to PrestaShop/PrestaShop#42162, which removes the id_country index on address from the install schema. That side only changes new shops - existing ones keep the index, and they are the ones with enough orders to feel it.

Why the index goes

It has no reader. Every core reference to address.id_country is a join against country that resolves through country.PRIMARY - Customer.php twice, CustomerAddressQueryBuilder, AddressQueryBuilder, and OrderCountriesChoiceProvider where the equality is against country_lang. No core query filters address by a literal country, and there is no foreign key on it.

What it does do is mislead the optimizer on the orders grid. Measured on a development shop with 60 005 orders and 45 006 addresses, running the join shape that grid builds:

	median of 3	plan
with id_country	152 ms	drives country_lang (ALL), then country, then address via id_country, Using temporary; Using filesort
without it	45 ms	drives orders on PRIMARY, rows=50, backward index scan, no filesort

PrestaShop/PrestaShop#41291 reports 4.7 s against 1.3 ms on 540k orders, which is the same plan flip at a larger scale.

Why a PHP callback and not a plain ALTER

9.0.1.sql drops an index directly, so the bare statement would match precedent. It is the wrong shape here: the workaround circulating for #41291 is to run

ALTER TABLE `ps_address` DROP INDEX `id_country`;

by hand, so on exactly the shops that were hurting the index is already gone, and DROP INDEX on a missing index is an error. MySQL has no IF EXISTS for indexes and DROP INDEX IF EXISTS is MariaDB only, so the check has to happen before the statement. The callback returns true when there is nothing to drop.

Version file

9.1.5.sql, matching the branch #42162 targets. If that PR is retargeted, this should move with it - say so and I will rename the file.

What I could not run

The module's .php-cs-fixer.dist.php loads a ruleset from the module's own vendor/, which I do not have installed, so I did not run it and am not claiming a pass. The file follows the shape of the existing callbacks - same header, same DbWrapper import, same signature style. php -l is clean.

[ps-jarvis]

Hello @boo-code!

This is your first pull request on autoupgrade repository of the PrestaShop project.

Thank you, and welcome to this Open Source community!

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud