Limit parameter count per query in Cache.removeChildren

[vijfhoek]

Fixes #25732 by limiting the amount of IDs in Cache.removeChildren's IN clauses to 2048 1000.

This number was determined by the reported (but untested by me) parameter limit of mssql being 2100 (which way under the parameter limits of the other database engines), rounding it down to the next power of 2 to provide a nice safety margin. 1000 was used elsewhere in the code, so that was used instead

In limited performance testing, this did not seem to have any negative impact on performance, with PostgreSQL benchmarks (on my laptop on battery power) even reporting a significant positive impact.

Testing

To test this, I've first created a bunch of folders, each with a bunch of subfolders, with a single file in each of those by running the following bash command in the data/admin/files/ directory:

for i in {0..100}; do
    mkdir -p test/spam$i/{0..1000}
    touch test/spam$i/{0..1000}/file
done

Now scan the directory (php occ files:scan --all) - this is gonna take a while, I recommend making a back-up of the database at this point to return to this state later). When this is done remove the test directory, then scan again.

This results in a $parentIds element count of over 100,000, which consistently reproduces the issue.

[kesselb]

Thanks 👍

The query should stay outside the loop if possible. #27187 as example.

[vijfhoek]

@kesselb Ah, thanks for the example. I'll edit this to make it more alike that one

[vijfhoek]

(Forgot to sign-off)

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