FAQ
A minor issue has come up in creating low-level bindings to libpq for
safe garbage-collected languages, namely that PQfinish is the only
(AFAICT) way to close a connection but also de-allocates the memory
used to represent the database connection. It would be preferable
to call PQfinish to free the memory in a finalizer, but appilcations
need a way to disconnect from the database at a predictable and
deterministic point in time, whereas leaving a bit of memory around
until the GC finally gets to it is relatively harmless. The
low-level binding has a couple of options:

1. Ignore the issue and allow for the possibility of a segfault if
the library is used incorrectly, which is not a good situation for
"safe" languages.

2. Create a wrapper that tracks whether or not PQfinish has ever been
called, so that attempts to use a connection afterwards can be turned
into native exceptions/other forms of error signaling. This kind of
solution can introduce their own minor issues.

3. Hack libpq to export closePGconn so that libpq can safely signal
the low-level bindings of the error when a connection is used after it
is disconnected, reserving PQfinish to run in a GC-triggered
finalizer. While this is a technically preferable solution, without
getting the change into upstream sources it is also a deployment
nightmare.

Is there any particular reason why closePGconn should not be exported
from libpq?

Best,
Leon

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grouppgsql-hackers @
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postedMay 14, '11 at 3:23p
activeMay 16, '11 at 12:17p
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