[Koha-bugs] [Bug 20271] Merge deleted biblio, biblioitems, biblio_metadata, and items tables with their "alive" cousins

[bugzilla-daemon at bugs.koha-community.org]

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=20271

--- Comment #131 from Benjamin Rokseth <benjamin.rokseth at deichman.no> ---
Hi, regarding performance and db update/migrate:
we have it in production now and tested quite abit up front.

db migrate took ~40sec as I recall (1,5M items and 400k biblios) which is far
less than the updates of statistics column took, for instance. We had 830
duplicate items that could not be moved. 

regarding performance there is nothing in this patchset that will degrade
performance, unless, say, you have a report query for all items, which now
would need to add 'WHERE deleted_on IS NULL' not to include deleted items

on the other hand, union queries of items and deleteditems are no longer
neccessary so statistical queries will be faster

When we move on to merge issues and reserves, the question is more relevant, as
10 years of checkout history might lead to 100M+ rows, but still, MySql is
capable of billions, and at that point its more a matter of indexes, RAM and
physics.

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