On Tue, 2008-09-02 at 15:51 +0300, Heikki Linnakangas wrote:
> The needs of access to the rows are so different that it seems best to
> me to delegate the buffering to the window function.
That seems sensible in some ways, not others.
Some of the window functions, like lead and lag merely specify window
size and shape for other functions to act upon. For those types of
request I don't see any need for custom functions, whereas for the
comparison/calculation functions there might be a need.
We don't need to implement all the things the SQL Standard calls window
functions with a 1:1 mapping to Postgres functions.
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