Re: [HACKERS] Hash Functions

On Fri, Aug 18, 2017 at 11:01 PM, Robert Haas <robertmhaas@gmail.com> wrote:

On Fri, Aug 18, 2017 at 1:12 PM, amul sul <sulamul@gmail.com> wrote:
> I have a small query,  what if I want a cache entry with extended hash
> function instead standard one, I might require that while adding
> hash_array_extended function? Do you think we need to extend
> lookup_type_cache() as well?

Hmm, I thought you had changed the hash partitioning stuff so that it
didn't rely on lookup_type_cache().  You have to look up the function
using the opclass provided in the partition key definition;
lookup_type_cache() will give you the default one for the datatype.
Maybe just use get_opfamily_proc?

Yes, we can do that for

​the ​

partitioning code, but my concern is a little bit

different.  I apologize, I wasn't clear enough. 

I am trying to extend hash_array & hash_range function. The hash_array and

hash_range function calculates hash by using the respective hash function for

the given argument type (i.e. array/range element type), and those hash

functions are made available in the TypeCacheEntry via lookup_type_cache(). But

in the hash_array & hash_range extended version requires a respective extended

hash function for those element type.

I have added hash_array_extended & hash_range_extended function in the attached

patch 0001, which maintains a local copy of TypeCacheEntry with extended hash

functions. But I am a little bit skeptic about this logic, any

​ ​

advice/suggestions will be

greatly appreciated. 

The logic in the rest of the extended hash functions is same as the standard

one.