Betteridge’s Law And Index Hints

Bert Wagner asks a question in his title, Should You Use Index Hints?  Those familiar with Betteridge’s Law of Headlines know the general answer already:

One way to “fix” a poor performing plan is to use an index hint.  While we normally have no control over how SQL Server retrieves the data we requested, an index hint forces the  query optimizer to use the index specified in the hint to retrieve the data (hence, it’s really more of a “command” than a “hint”).

Sometimes when I feel like I’m losing control I like using an index hint to show SQL Server who’s boss.  I occasionally will also use index hints when debugging poor performing queries because it allows me to confirm whether using an alternate index would improve performance without having to overhaul my code or change any other settings.

About the only place I consistently use index hints is with filtered indexes, where the combination of parameter sniffing and inexactitude in filters will convince the optimizer that the filtered index isn’t helpful when it really is.

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