Hi tb,
unfortunately this report is not very useful because it does not describe the problem well. If you have time and can still reproduce the problem, please read https://www.mediawiki.org/wiki/How_to_report_a_bug and add a more useful description to this report by describing what the bug is, and/or what "slow" exactly means, plus what you want to see "explained" here.

(In reply to comment #1)

Hi tb,
unfortunately this report is not very useful because it does not describe the
problem well. If you have time and can still reproduce the problem, please
read
https://www.mediawiki.org/wiki/How_to_report_a_bug and add a more useful
description to this report by describing what the bug is, and/or what "slow"
exactly means, plus what you want to see "explained" here.

…

EXPLAIN is a MySQL function.

Apologies if my initial report was unclear. Per bug #48875, it is not possible for tool labs end users to use the MariaDB EXPLAIN facility. One of my tools is running more slowly that I expected; I have tracked this down to a particular SQL query it.

I am requesting that someone with relevant permissions connect to enwiki.labsdb, execute the command below and return the result to me please. This should (hopefully) give me the information I need to resolve the problem.

EXPLAIN SELECT count(1) AS 'howmany'
FROM enwiki_p.pagelinks l
INNER JOIN p50380g50491_rlrl_enwiki.suggestions s ON

l.pl_namespace = s.sug_orig_ns AND l.pl_title = s.sug_orig

WHERE l.pl_from = 38136839
AND s.sug_status >= 0;

• 1. row ******* id: 1 select_type: SIMPLE table: pagelinks type: ref

possible_keys: pl_from,pl_namespace

     key: pl_from
 key_len: 4
     ref: const
    rows: 1205
filtered: 100.00
   Extra: Using index

• 2. row ******* id: 1 select_type: SIMPLE table: s type: ref

possible_keys: PRIMARY,sug_orig

     key: PRIMARY
 key_len: 4
     ref: enwiki.pagelinks.pl_namespace
    rows: 151
filtered: 100.00
   Extra: Using where