The extension has been adding growthexperiments-homepage-variant user properties for a long time since the experiments manager is always instructed to set a feature variant and there has not been set static default for it.
Numbers in eswiki show that in 85% of those properties have "control" as its value.
wikiadmin2023@10.64.0.47(eswiki)> select count(*) from user_properties where up_property='growthexperiments-homepage-variant'
-> ;
+----------+
| count(*) |
+----------+
| 544967 |
+----------+
1 row in set (0.562 sec)
wikiadmin2023@10.64.0.47(eswiki)> select count(*) from user_properties where up_property='growthexperiments-homepage-variant' and up_value='control';
+----------+
| count(*) |
+----------+
| 464608 |
+----------+
1 row in set (13.518 sec)The task is to set the control variant as the default so we can safely remove a the unnecessary rows. The rest of variants (except of oldimpact) are at the moment treated as the "control" variant so it could be decided the delete them as well.
The intent is to make enough savings in the user_property table that the rows the Community Updates experiment will introduce ( upper bound 15000) does not suppose a problem.
See also T374471: Decide which bucketing/variant assignment system should we use.