On Mon, Jul 20, 2015 at 8:40 AM, sudalai <sudala...@gmail.com> wrote: > >>I don't think so, because arrays can contain duplicates. > > I just add two element to the array. One for INITCOND value NULL, second > for first row value. > So Array size is always 2. So no duplicates. > >>rhaas=# select coalesce(first(x.column1), 'wrong') from (values >>(null), ('correct')) x; > >coalesce >>---------- >> wrong >>(1 row) > It works correct.. > I didn't said it returns, first non-null value for a column from aggregate > window. > I said my implementation returns first row value for a column. > Here first row element is "null ", hence it returns null. > > > check this.... > db=# select > db-# coalesce(first(x.column1),'null') as col1 , > db-# coalesce(first(x.column2),'null') as col2, > db-# coalesce(first(x.column3),'null') as col3 > db-# from (values (null,'abc',null), ('correct','wrong','notsure'), > ('second','second1','second3')) x > db-# ; > col1 | col2 | col3 > ------+------+------ > null | abc | null > (1 row) > > Its work correct. It returns first row value for a column.
I was able to get ~45% runtime reduction by simply converting "two_value_holder" from sql to plpgsql. SQL functions (unlike pl/pgsql) are parsed and planned every time they are run unless they are inlined. Our aggregation API unfortunately is a hard fence against inlining; solving this is a major optimization target IMO. merlin -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers