The following query (used in dashboard /svn widget) is slow
SELECT svn_commits.revision as revision, svn_commits.id as commit_id, svn_commits.description as description, svn_commits.date as date, svn_commits.whoid FROM svn_commits WHERE svn_commits.group_id=XXX ORDER BY revision DESC LIMIT 0,5;
The index used for query is only the group_id one, so here if a project have many commit the request query all rows of project to only retrieve 5 rows.