MapServer to pass filter to OGR

[Trevor.Tracey-Patte@…]

Could you please modify MapServer to pass the FILTER parameter to OGR when it 
starts with 'WHERE' for Oracle Spatial connections to allow the database to do 
the filtering and not use MapServer regexp matching.
I have discussed this with Frank Warmerdam and he has agreed that he will 
implement this in OGR.

[fwarmerdam]

Accepting.  I'll start prototyping this in the 4.5 tree tonight. 

[fwarmerdam]

Note the proposed change is to modify the FILTER handling in mapogr.cpp
so that if the filter is prefixed by WHERE it will be passed off to the
OGRLayer::SetAttributeFilter() method instead of processing it in MapServer.
For underlying drivers like Oracle Spatial (or any SQL aware RDBMS) this can
give dramatic performance improvements. 

But the change will apply to all OGR datasources. 

[fwarmerdam]

Committed preliminary support for the pass-through filtering in mapogr.cpp. 

If the string following the FILTER keyword is prefixed by "WHERE " then it will
pass the statement off to OGR.  The rest of the statement must be a valid
WHERE clause suitable for use with OGRLayer::SetAttributeFilter().  

Test case in msautotest now for this case in msautotest/misc/ogr_attrfilter.map.

Example:
  FILTER "WHERE EAS_ID in (179, 173)"

This change is *only* in MapServer 4.5.

[warmerdam]

Closing as this is completed.