[zzzeek]

To be fair this is a problem inherent to databases in general. You can have hand written queries that perform badly due to structure or query frequency as well which are not apparent until the dataset grows. The ORM should make it easier to rectify such situations (eg drop in an eager loading directive) vs having to restructure hand-written routines for similar effects.

[magicalhippo]

Indeed, even with query analyzer you might see say table scans instead of index scan just because the DB realizes just scanning the 100 rows you got is faster than trying to use an index.

So without a large number of rows it can be hard to know what it will actually do.