On 22/09/14 22:58, Merlin Moncure wrote:
Meh. Those aren't comparable. TEMPORARY TABLES/INDEXES/... all live
beyond a single statement. What's being discussed here doesn't.
Even if that wasn't true, 'DO' doesn't involve changes to system
catalogs whereas temporary functions would. With a little imagination
I could come up a with a scenario involving a script of a whole bunch
of repeated trivial DO statements which would involve a lot less
beating on the system catalogs.
When the data-modifying-with feature was considered, an implementation
that relied on temp tables was rejected at least in part because of
system catalog thrash and poorer performance for very trivial queries.
So, to me, DO vs CREATE FUNCTION has nothing to do with passing
arguments and/or returning data. It has to do with lifespan; single
call of the function body only, use DO, otherwise, create a function.
Actually same thing happened with the DO implementation itself -
creating anonymous/hidden temporary functions in the background was also
considered but was decided it's not acceptable (for similar reason temp
tables were rejected for WITH).
So we decided at least twice already that this kind of solution is bad,
I don't know of any change that would invalidate the reasons for
deciding that way so I don't see why they would suddenly become
acceptable...
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