Hello 2010/9/22 Hitoshi Harada <umi.tan...@gmail.com>: > 2010/9/22 Pavel Stehule <pavel.steh...@gmail.com>: >> Hello >> >> I found probably hard problem in cooperation with window functions :( >> >> tuplesort_begin_datum creates child context inside aggcontext. This >> context is used for tuplestore. But when this function is called from >> WindowAgg_Aggregates context - someone drops all child context every >> iteration, and then tuplestore state is invalid. For this moment we >> can block using a median function as window function, but it should be >> solved better - if it is possible - I don't see inside window function >> implementation. > > Does it happen when the window frame starts from not UNBOUNDED > PRECEDING? In those cases, nodeWindowAgg tries to discard all > aggregate contexts and to initialize the aggregate state. AFAIK the > memory context is brand-new although it was reset and its children > deleted, so if the function is well-formed and initializes its state > on NULL input, it doesn't cause a problem.
maybe I was confused. I found a other possible problems. The problem with median function is probably inside a final function implementation. Actually we request possibility of repetitive call of final function. But final function call tuplesort_end function and tuplesort_performsort. These function changes a state of tuplesort. The most basic question is "who has to call tuplesort_end function and when? Regards Pavel Stehule > > > Regards, > > > -- > 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
