Steps:
[x] Implement update script to add new column term_full_entity_id and associated indexes {T162533}
[x] DBA to add new column term_full_entity_id (but possibly not yet the indexes) {T162539 }
[ ] Switch to updating both, the old and the new column {T167229}, {T165197}
[ ] Populate new column using maintenance script: {T171460}
[ ] DBA to create new indexes using new column, if not already done when the column was created (needs lots of disk space)
[ ] Switch to queries using the new column
[x] join against page and redirect table instead of wb_entity_per_page {T162673}
[ ] make sure we are not using old and new indexes at once now, since they need a lot of RAM
[ ] Switch off writing to the old column (this breaks compat for scripts on ToolLabs)
[ ] DBA to drop old column and indexes (free a lot of disk space)