Currently, the query system will clear the entire collection plan cache when any given index is hidden. This causes every subsequent query to go through planning which can be expensive and, depending on the workload, create a "multiplan storm" situation. This ticket proposes an approach that looks at the indexes used for each cached plan and only clears the entries which use the hidden index.

Note that this is particularly impactful for performance advisor, since users are first advised to hide an index before dropping altogether if it's no longer useful.