index-tuning

Do Index Changes Remove Execution Plans from Cache?

Do Index Changes Remove Execution Plans from Cache?

When you modify the indexes on a table, SQL Server needs to reconsider how it executes queries that reference that table. But the way this appears when you’re looking at your execution plan cache is far from obvious: Impacted query plans are NOT removed from cache at the time you change an index. The next time the query is executed, it will be recompiled, and the new plan and related execution information will be placed in cache.
DBCC CLONEDATABASE Does NOT Clone Index Usage Statistics

DBCC CLONEDATABASE Does NOT Clone Index Usage Statistics

The word ‘statistics’ is awfully confusing in SQL Server

It can mean “statistics” themselves – little objects that describe the distribution of data in columns or indexes to help the optimizer.

Or it can mean “usage statistics” -  dynamic management views that let you see how many times an index has been used or requested, how many times a query has been run, that kind of thing.