Denys Rtveliashvili r...@icloud.com writes:
My function neeeds to call a third-party library which would create a state
and then that state should be kept for the duration of the current query. The
library can deallocate that state in a correct way.
I understand that fn_extra is normally used for this and usually the state is
created in a memory context which is deallocated at the end of the query. So
normally it is not an issue. However, I cannot make that library use
PostgreSQL utilities for memory management.
I am afraid that for long-running sessions it may cause serious memory leaks
if they do not deallocate state correctly and in a timely manner.
Is there a mechanism for adding a finalizer hook which would be called and
passed that pointer after the query is complete? Or perhaps there is another
mechanism? I looked in the documentation and in the source but I do not see
it mentioned.
In HEAD, you could use a memory context reset callback for this purpose.
I don't believe there's any fully satisfactory solution in the released
branches; the closest you could get is an ExprContext callback, which
has the fatal-for-this-purpose defect that it's only called on successful
query completion, not if an error occurs.
regards, tom lane
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