On Thu, 28 Oct 2010, Robert Muir wrote:
On Thu, Oct 28, 2010 at 8:35 PM, <karl.wri...@nokia.com> wrote:
In database queries, it is often useful to treat an empty value specially, and
be able to search explicitly for records that have (for instance) no field X,
or no value for field X. I can't regurgitate offhand all the precise
situations that I've used this and claim that they would apply to a search
engine, but it is conceivable that it could be helpful to somebody. Would your
proposed change preclude current or future support for such null queries?
in a database, not having a value for field X is 'null'.
1. null is different than empty term.
2. comparing this concept with an inverted index vs a database record
really isn't a comparison.
by not having 'empty' terms (terms of length=0), what searches would
be affected.
I still haven't heard a real use case (though surely perhaps there is
someone abusing this somehow), but there is a serious performance trap
that is definitely real.
I've used this in a URL index. I needed to be able to distinguish between
searching URLs that had, say, no path, from searching URLs without matching
the path component. The absence of path was represented with an empty token
in the path field.
Andi..
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