Reg Me Please wrote:
Il Wednesday 21 November 2007 20:22:46 Joe Conway ha scritto:
Reg Me Please wrote:
The meaning is that an entity called by the value of "item" has a number
of properties called by "property" with value "prop_value".
So, for a single "item" there can be many different "property" each with
its own value.
A filter is a list of property values needed to qualify an entity as
"good". An entity evaluates as good only when all property values in the
filter match the ones associated to an item in t_data.
What's missing to me is how to apply a filter to the t_data and get the
list of the items that evaluate good.
I haven't played with it myself, but it seems to me that you could do
this with an inner join of two crosstabs -- one on t_data and one on the
filters (i.e. you join on the columns of the filter crosstab to the
matching ones in the t_data crosstab).
Joe
This is a good point.
I just need to avoid doing crosstabs over a very large t_data: I fear it'd
kill the application.
Yeah, I suspect as much too.
You might want to create a custom filter function based on the
crosstab_hash function in contrib/tablefunc. The basic elements are
there. Instead of building return tuples you could do the filtering and
return a boolean value for each row key or something like that.
Joe
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