trying to use spatial index for fast retrieving

[Jo Ha]

Hi

I have intervals on x axis (a,b) and i'm trying to store them in Linestring(a 0 , b 0)
i create spatial index on the right column and inserted a few hundrends of intervals(a,b)

i try to find out if point $p lies inside one of them by using the following:

$p=78 // (78,0)
SELECT AsText(interval) FROM xaxis WHERE Contains(interval,GeomFromText('POINT(".$p." 0)'))

when i look at EXPLAIN i see that although there is a spatial index on 'interval' column it is not used.

also index cardinality is shown to be 1... like i have only one unique value...this is odd...

someone knows maybe what's wrong with what i'm doing?

thank you