> On 11/19/2012 08:41 PM, matt@xxxxxxxxxx wrote: >> I want to process all the records in a table through a C-language (well, >> C++) function (i.e. one function call per row of the table) in such a >> way >> that the function hangs onto its internal state across calls. Something >> like >> >> SELECT my_function(a, b, c) FROM my_table ORDER BY d; >> >> The value returned in the last row of the table would be the result I'm >> looking for. (This could be neatened up by using a custom aggregate and >> putting my calculation in the sfunc but that's a minor detail). > [snip] >> Alternatively, use this in a custom aggregate and make the ffunc do the >> garbage collection, which should prevents leakage altogether. > You don't generally need to do this cleanup yourself. Use appropriate > palloc memory contexts and it'll be done for you when the memory context > is destroyed. > > I would want to implement this as an aggregate using the standard > aggregate / window function machinery. Have a look at how the existing > aggregates like string_agg are implemented in the Pg source code. Thanks for your reply. A follow-up question: to use the palloc/pfree functions with a C++ STL container, do I simply give the container an allocator which uses palloc and pfree instead of the default allocator, which uses new and delete? Matt -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
