Postgresql function failed with "relation with OID xxxxx does not exist" - postgresql

Question

I am trying to extend a item profile table by parsering the its part_number column further down into properties. It works fine outside a function.
ALTER TABLE tbl_item_info
ADD prop1 varchar(2),
ADD prop2 varchar(1),
ADD prop3 numeric(4,3);
UPDATE tbl_item_info
SET prop1 = substr(part_num,5,2)
, prop2 = substr(part_num,7,1)
, prop3 = to_number( substr(part_num,8,5) , '9G999')
WHERE ARRAY[left(part_num,3)] <# ARRAY['NTX','EXC'] ;
But when I try to put the statements into a function. It always fail with error "relation with OID xxxxx does not exist" pointing to the UPDATE statements.
I have no clue what it is trying to say. Any idea why ?

Answer 1

I wish I had a definitive answer, but this seems to be related to a known bug in PostgreSQL as described here:
https://github.com/greenplum-db/gpdb/issues/1094
Bear in mind that the greenplum implementation of PostgreSQL is proprietary to Dell EMC, however, the core code issue is likely the same for all major PostgreSQL distributions. I am still researching this to determine if there is a good resolution to the problem. The database in which I experienced a markedly similar error is not the greenplum implementation of PostgreSQL. The error was thrown when I called the pg_relation_filepath() function in a query on an oid that was dynamically obtained from a record in the pg_class table that should have had an associated external file in a subdirectory of the ./base/ path. The error that was thrown was:
ERROR: relation "pg_toast_34474_index" does not exist
The point here is that for a toast entity to exist, it is supposed to be tied to another relation and acts as a reference to additional files created out on the storage media to accommodate additional data that does not fit into the owning relation's top level file - in this case, most likely a table. But when I search for the owning relation's oid (34474), the owner doesn't exist. Since the owner doesn't exist I think the logic assumes that the toast entity doesn't either, even though it has a record in the pg_class table.
This is as close as I can get to a root cause for now. Although the above link suggests code to improve the issue is supposed to have been released in version 8.3, my database has been upgraded from version 8.1 to version 9.4.7, so it appears that even though code may have improved between those two version to prevent new occurrences of the problem, if the problem was created before the database was upgraded, the newer code does not know how to reassemble the tinker toys left behind from issues created by this apparent bug before the fix was implemented.
At present I am investigating if a PLPGSQL function can wrap and trap the error for all relations so I can identify which ones have the problem (as well as to solve my original problem of determining which relation is hosted in a specific file that the server.postmaster log tells me it is unable to read from - hopefully it is just an index I can drop/create).

Answer 2

I found this issue at server 13.7. It was not at server 14.3.
It happened when I changed the signature (parameters) of the stored procedure:
SQL Error [42883]: ERROR: function with OID 894070 does not exist
I removed the old procedure and created new one.
But when I called a function which used that procedure it triggered the error.
To fix it I recreated the function which used changed object.
So general rule:
look where error happens, make sure to recreate object that triggers error, and recompile the code which uses it.
Hope it will help.