How are python functions compiled and stored in PostgreSQL?

Question

Scenario:

I have a python function on disk somewhere.
I compile a plpythonu function in pg server, which is referencing that python function from step 1 on disk.
I change something in python function (from step 1).
If I compile plpythonu function (from step 2), change done in step 3 does not take effect when calling from pg server.

Example of such functions can be seen in my other question: Python function hangs when called from within sql function

My assumptions (what this seems like to me):

PG server stores both the python function (step 1) code and plpythonu code somewhere at first compilation, where ?
It does not check again the linked function (step 1) when recompiling (step 4) the plpythonu function. Can this behavior be changed or affected somehow ?

If these assumptions are wrong, please also correct me and explain. Or even point me to documentation where this can be found, I have not succeeded in finding it yet.

Craig Ringer · Accepted Answer · 2015-12-02 02:52:05Z

1

PG server stores both the python function (step 1) code and plpythonu code somewhere at first compilation, where ?

The Python code for the pl/python function its self (but not any modules, libraries, etc) is stored in the pg_proc table in the database.

The compiled Python bytecode gets stored in the syscache in memory when it's first run by a given backend. It isn't updated after that if files on disk change. New connections will see the new code, old connections the existing code.

answered Dec 2, 2015 at 2:52

Craig Ringer

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1 Comment

M_M Over a year ago

Thank you. Now that you said it, it makes sense. Being used to work with just the classic functions (plpgsql) where recompilation is visible instantly, in same connection, I intuitively did not think of any different approach in my testing (trying changes on new connection).

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