Constraint exclusion oddity with composite index

Hello,

Assume the following:

index on: (id, adate)

constraint CHECK(adate > '01-01-2007' AND adate < '04-01-2007');

The planner will not use the index listed above. It does work if we have 
an index on just timehit in addition to the above. (of course)

Is this expected?

Joshua D. Drake

P.S. 8.1.9

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