Horton

Re: Fix for recursive plpython triggers

Andreas Karlsson <andreas@proxel.se>

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From: Andreas Karlsson <andreas@proxel.se>
To: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@lists.postgresql.org
Date: 2024-05-08T07:03:01Z
Lists: pgsql-hackers 
On 5/4/24 10:16 PM, Tom Lane wrote:
> This fixes bug #18456 [1].  Since we're in back-branch release freeze,
> I'll just park it for the moment.  But I think we should shove it in
> once the freeze lifts so it's in 17beta1.
There is a similar issue with the return type (at least if it is a 
generic record) in the code but it is hard to trigger with sane code so 
I don't know if it is worth fixing but this and the bug Jacques found 
shows the downsides of the hacky fix for recursion that we have in plpython.

I found this issue while reading the code, so am very unclear if there 
is any sane code which could trigger it.

In the example below the recursive call to f('int') changes the return 
type of the f('text') call causing it to fail.

# CREATE OR REPLACE FUNCTION f(t text) RETURNS record LANGUAGE 
plpython3u AS $$
if t == "text":
     plpy.execute("SELECT * FROM f('int') AS (a int)");
     return { "a": "x" }
elif t == "int":
     return { "a": 1 }
$$;
CREATE FUNCTION

# SELECT * FROM f('text') AS (a text);
ERROR:  invalid input syntax for type integer: "x"
CONTEXT:  while creating return value
PL/Python function "f"

Andreas

Commits

  1. Fix recursive RECORD-returning plpython functions.

  2. Don't corrupt plpython's "TD" dictionary in a recursive trigger call.