Re: Detection of nested function calls

On Fri, Oct 25, 2013 at 10:18 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Hugo Mercier <hugo(dot)mercier(at)oslandia(dot)com> writes:
>> PostGIS functions that manipulate geometries have to unserialize their
>> input geometries from the 'flat' varlena representation to their own,
>> and serialize the processed geometries back when returning.
>> But in such nested call queries, this serialization-unserialization
>> process is just an overhead.
>
> This is a reasonable thing to worry about, not just for PostGIS types but
> for many container types such as arrays --- it'd be nice to be able to
> work with an in-memory representation that wasn't just a contiguous blob
> of data. For instance, assignment to an array element might become a
> constant-time operation even when working with variable-length datatypes.

I bet numeric could benefit as well. Essentially all of the
operations on numeric start by transforming the on-disk representation
into an internal form used only for the duration of a single call, and
end by transforming the internal form of the result back to the
on-disk representation.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company