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Ticket UUID: 9d0044f15436d620ec23442410107e26eb0776ff
Title: xFilter not using correct index?
Status: Closed Type: Incident
Severity: Important Priority: Medium
Subsystem: Virtual_Table Resolution: Works_As_Designed
Last Modified: 2015-02-27 20:23:39
Version Found In:
User Comments:
anonymous added on 2015-02-27 15:20:23:

I'm implementing a virtual table in .NET for accessing a custom data source. 
It's going rather well, but I have an issue regarding BestIndex and Filter.

My index (basically a .NET dictionary) isn't being used for queries in the following form:
select ... from ... where columnX='...' OR columnX='...'

It seems that if the same column is used twice and there is an 'OR' in between, the following happens:
- my BestIndex is called twice, but the constraint in the first call is unusable so I can't add it to ConstraintUsages. The second call works fine. 
- the Filter method is called once but it seems I get the index from the first call to BestIndex (the one with the unusable parameter) so a sequential scan results 

Is this a bug or am I missing something?


mistachkin added on 2015-02-27 20:23:39:
The xBestIndex can be called more than once.  If it is called more than once,
the planner chooses the scan with the lowest cost.  And that's the one xFilter
is called with.