On Thu, Mar 29, 2012 at 7:38 PM, Peter Eisentraut <pete...@gmx.net> wrote: > On tis, 2012-03-27 at 00:53 +0100, Greg Stark wrote: >> Hm. So my original plan was dependent on adding the state-merge >> function we've talked about in the past. Not all aggregate functions >> necessarily can support such a function but I think all or nearly all >> the builtin aggregates can. Certainly min,max, count, sum, avg, >> stddev, array_agg can which are most of what people do. That would be >> a function which can take two state variables and produce a new state >> variable. > > This information could also be useful to have in PL/Proxy (or similar > FDWs) to be able to integrate aggregate computation into the language. > Currently, you always have to do the state merging yourself. >
I don't know exactly how PL/Proxy or pgpool accomplish the multi-phase aggregate, but in theory the proposal above is state-merge function, so it doesn't apply to general aggregate results that passed through the final function. Of course some functions that don't have final functions are ok to call state-merge function on the results. Thanks, -- Hitoshi Harada -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
