From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of Michael Giannakopoulos Sent: Thursday, November 29, 2012 4:07 PM To: pgsql-general@xxxxxxxxxxxxxx Subject: About aggregates... Hello guys, I would like to ask if there is any way to make an aggregate function to take a set of tuples as an input variable. I know that an actual aggregate function receives each tuple one at a time and process it on the fly. However I want to store tuples in an incremental fashion so as to process them in a batch approach in the finalaggr function. Think for example implementing logistic regression (which is an OLAP query by its nature). I want to support it with the current features that PostgreSQL provides from which the closest feature is an aggregate. However an aggregate function feeds me one a tuple for each call, but I would like to have access to a batch of tuples per function call. Is there any possible way to perform something like this? Thank you very much for your time, Michael ===================================== Not sure how the system would decide between (1-at-a-time) and (everything-at-once). The only approach I can think of would be to build out an array of "tuples" and then have the aggregate process a single array value each time. As Ondrej indicates in parallel you can try making use of Windows (probably with a FRAME definition) as well. Hopefully this helps but I am not familiar enough with the use-case to be more specific. David J. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
