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The Downside Risk of Index Hints

Chad Callihan explains why you should be careful before deploying code which uses index hints:

This might be good enough…for now. The potential issues with index hints can be more about the future than the present. You might come along later on and think “why not use an index to cover the whole query?” We can add the index:

But if our query is still written to include the index hint (in a stored procedure for example) the new index is not going to matter. The old index is still forced to be used. Even if something better comes along, you’re going to need to modify the query in addition to adding the better index. If an index was added for a completely separate query but would also be an improvement for the query in question, it’s also not going to get by the index hint.

Click through for additional problems which can crop up as you use index hints. This isn’t a big argument against using them at all, but rather understanding (and remembering!) where you do use them and making sure that’s communicated well to the entire team, including future you.

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