[Koha-bugs] [Bug 24185] 'If all unavailable' state for 'on shelf holds' makes holds page very slow if there's a lot of items

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

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=24185

--- Comment #1 from Andrew Nugged <nugged at gmail.com> ---
Created attachment 96079
  -->
https://bugs.koha-community.org/bugzilla3/attachment.cgi?id=96079&action=edit
Bug 24185: 'If all unavailable' for 'on shelf holds' makes holds page slow

When "reserve/request.pl -> C4/Reserves.pm::IsAvailableForItemLevelRequest"
called many times with hundred of items and "on shelf holds" parameter set to
"If all unavailable" for these items+patron, it goes very slow.

This happens because in subloop there are re-checking if all other item
unavailable so it is O(n^2) and it re-checks each time a lot of the same info
for each item with repeating DB/data requests, these three:
  - GetBranchItemRule (per item type)
  - IsItemOnHoldAndFound (per item)
  - notforloan (per item)

Proposed fix: I created patch to have in-variable cache in upper-level
subroutine before entering the first "items" loop and passing that hash
reference down into subs to cache these three values by keys per-item and
per-item-type.

It is simplest way to make it fast without re-thinking pretty complicated whole
algorithm and business logic, and, when tested by speed it gave big improvement
in execution time.

How to reproduce:

1) on fresh installed kohadevbox create/import one book,
record that biblionumber for later use it in down below,

2) add 100 items for that book for some library,

3) find some patron, that patron's card number we will
use as a borrower down below to open holds page,

4) check for the rule or set up single circulation rule
in admin "/cgi-bin/koha/admin/smart-rules.pl",
so that rule will match above book items/library/patron,
check that rule to have non-zero number of holds (total, daily, count) allowed,
and, IMPORTANT: set up "On shelf holds allowed" to "If all unavailable",
("item level holds" doesn't matter).

5) open "Home > Catalog > THAT_BOOK > Place a hold on THAT_BOOK" page
("holds" tab), and enter patron code in the search field,
or you can create direct link by yourself, for example in my case it was:
/cgi-bin/koha/reserve/request.pl?biblionumber=4&findborrower=23529000686353

6) it should be pretty long page generation time.

I tested on my computer in VirtualBox for this page generation times,
(stats below is for many runs and smallest value taken from similar in a
repetition)

*** "On shelf holds allowed" != "If all unavailable":
  100 items:    5 seconds,
  200 items:   10 seconds,
  300 items:   11 seconds,

*** "On shelf holds allowed" == "If all unavailable":
  100 items:    50 seconds,
  200 items:   3.1 minutes,
  300 items:   7.0 minutes,

*** "On shelf holds allowed" == "If all unavailable" with cache:
  100 items:    7 seconds,
  200 items:   20 seconds,
  300 items:   38 seconds,

Upper last one block with times with this in-var-cache solution.

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