[wp-meta] [Making WordPress.org] #8184: Plugin search API returns different result ordering when only per_page differs

[Making WordPress.org]

#8184: Plugin search API returns different result ordering when only per_page
differs
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 Reporter:  yani.iliev        |      Owner:  (none)
     Type:  defect (bug)      |     Status:  new
 Priority:  normal            |  Milestone:
Component:  Plugin Directory  |   Keywords:
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 The plugin search API at api.wordpress.org/plugins/info/1.2/ returns
 results in a different order depending on the per_page parameter, even
 when the search query and page number are identical.

 **Steps to reproduce:**

 1. Request:
 https://api.wordpress.org/plugins/info/1.2/?action=query_plugins&request[search]=backup&request[page]=1&request[per_page]=20
 2. Request:
 https://api.wordpress.org/plugins/info/1.2/?action=query_plugins&request[search]=backup&request[page]=1&request[per_page]=36
 3. Compare the slug order of the first 20 results.

 **Expected:** The first 20 results from both requests should be in the
 same order, since only the number of returned items differs.

 **Actual:**   Both requests return the same set of 20 slugs, but the
 ordering differs in two places:


 {{{
   ┌──────────┬─────────────────────────┬─────────────────────────┐
   │ Position │       per_page=20       │       per_page=36       │
   ├──────────┼─────────────────────────┼─────────────────────────┤
   │ 3        │ all-in-one-wp-migration │ duplicator              │
   ├──────────┼─────────────────────────┼─────────────────────────┤
   │ 4        │ duplicator              │ all-in-one-wp-migration │
   ├──────────┼─────────────────────────┼─────────────────────────┤
   │ 16       │ wp-mail-smtp            │ backup                  │
   ├──────────┼─────────────────────────┼─────────────────────────┤
   │ 17       │ backup                  │ wp-mail-smtp            │
   └──────────┴─────────────────────────┴─────────────────────────┘

 }}}

 **Impact:** wordpress.org plugin search uses per_page=20 while wp-admin
 Add Plugins uses per_page=36. This means users see different plugin
 rankings for the same search term depending on where they search. A plugin
 can appear at position 3 on wordpress.org but position 5 in wp-admin, or
 vice versa.

 **Likely cause:** Elasticsearch's default ''query_then_fetch'' search type
 computes relevance scores per-shard using local term frequencies. Changing
 the result set size affects how shard results are merged, producing
 inconsistent global ordering. Using ''dfs_query_then_fetch'' would ensure
 consistent scoring across request sizes.

-- 
Ticket URL: <https://meta.trac.wordpress.org/ticket/8184>
Making WordPress.org <https://meta.trac.wordpress.org/>
Making WordPress.org