Hello updated version * memsort removed * window aggregate support blocked
Regards Pavel 2010/10/1 Pavel Stehule <pavel.steh...@gmail.com>: > 2010/10/1 Hitoshi Harada <umi.tan...@gmail.com>: >> 2010/10/2 Tom Lane <t...@sss.pgh.pa.us>: >>> Hitoshi Harada <umi.tan...@gmail.com> writes: >>>> 2010/10/2 Tom Lane <t...@sss.pgh.pa.us>: >>>>> The implementation I would've expected to see is to do the sort and then >>>>> have two code paths for retrieving the median, depending on whether the >>>>> sort result is all in memory or not. >>> >>>> Hm? The problem we encountered in the middle of the patch is there is >>>> no chance to call tuplesort_end if median is called in moving frame >>>> window aggregate because final function is called multiple times >>>> during moving. >>> >>> Well, if you haven't got a solution for that, then this patch isn't >>> ready for prime time. >>> >>> It's entirely possible that median as a window function is intractable. >>> I'd rather have it throwing error than offer an implementation that will >>> fall over as soon as the window gets large. >> >> Well, that sounds like the conclusion. It is a shame, but we have to >> throw an error from median() in the window aggregate, if Pavel does >> not have any better solution. And as an aggregate function only, the >> patch is ready if the window-related parts are removed. >> > > I am sorry - I don't have a better solution. Classic algorithm isn't > well for window aggregate - it needs a sort after any append a new > item. Maybe we can use a separate functionality based on estimated > values for a windows. I read some articles about it. But this is work > on longer time - all articles about this topic are experimental. More > I am not mathematician - so I am not able to review these methods. > Today or tomorrow I'll send a updated patch without support a window > aggregates. > > Regards > > Pavel Stehule > >> Regards, >> >> >> -- >> Hitoshi Harada >> >
median.diff
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