While working on
MDL-27071 it was clear that IN() clauses using BIG number of params don't scale properly and should be considered abuse.
This is about to decide:
1) if we should start showing some DEV warning when the number of elements is over, say, 500 recommending to change the code to use one of these:
- PHP chunks.
- temp tables.
2) fix bulk user actions with some of the techniques above because they are abusing the IN() clause (see
MDL-27071 and linked issues there).