SQL Server Execution Plans - Red Gate Software

Chapter 5: Controlling Execution Plans with Hints
SELECT *
FROM Person.vStateProvinceCountryRegion;
Listing 5.26
Figure 5.25 shows the resulting execution plan.
Figure 5.25
An indexed view is effectively a clustered index, so this execution plan makes
perfect sense since the data needed to satisfy the query is available in the
materialized view. Things change, as we see in Figure 5.26, if we add the query
hint, OPTION (EXPAND VIEWS).
Figure 5.26
Now we're no longer scanning the indexed view. Within the optimizer, the view has
been expanded into its definition so we see the Clustered Index Scan against the
Person.CountryRegion and Person.StateProvince tables. These are then joined
using a Merge Join, after the data in the StateProvince stream is run through a Sort
operation. The first query ran in about 214ms, but the second ran in about 342ms, so we're
talking a substantial decrease in performance to use the hint in this situation.
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