Re: Designing an extension for feature-space similarity search

Jay Levitt  writes:
> Perfect. Composite types are exactly what I need here; the application can 
> declare its composite type and provide distance functions for each member, 
> and the extension can use those to calculate similarity. How do I introspect 
> the composite type's pg_class to see what it contains? I assume there's a 
> better way than SPI on system catalogs :)

Definitely.  Take a look at record_out, record_cmp, and sibling
functions on generic composites (src/backend/utils/adt/rowtypes.c).
You might or might not feel like wiring in more assumptions than those
have about the possible contents of the record type.
		regards, tom lane