Thread: ALTERed DEFAULTS not visible to PL/pgSQL cached plans

Folks,

Version: 8.1.3
Platform: SuSE Linux, GCC
Severity: mild data corruption
Reproducability: 100%

Steps to Reproduce:
(sample code attached)
1) Create a table.
2) Create a function which inserts a row into that table.
3) Run the function once.
4) ALTER the table with a new column and SET DEFAULT for that column.
5) Run the function again.
6) Re-load the function (via REPLACE)
7) Insert one more row using the function.
8) The table will have NULL values in the first TWO rows, not the first ONE
row as it should.   This is because the DEFAULT value is not being "seen"
by the cached plan of the function. As an example, the attached code
produces:

ltreetest=# select * from bugtest;
 id |      name      | is_true
----+----------------+---------
  1 | Before ALTER   |
  2 | Look, its null |
  3 | Now its true.  | t

When it should produce:

ltreetest=# select * from bugtest;
 id |      name      | is_true
----+----------------+---------
  1 | Before ALTER   |
  2 | Look, its null | t
  3 | Now its true.  | t

--
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

Josh Berkus wrote:

> Steps to Reproduce:
> (sample code attached)
> 1) Create a table.
> 2) Create a function which inserts a row into that table.
> 3) Run the function once.
> 4) ALTER the table with a new column and SET DEFAULT for that column.
> 5) Run the function again.
> 6) Re-load the function (via REPLACE)
> 7) Insert one more row using the function.
> 8) The table will have NULL values in the first TWO rows, not the first ONE
> row as it should.   This is because the DEFAULT value is not being "seen"
> by the cached plan of the function.

I don't think this is really surprising, because the plan of the insert
query will be saved in the function parsetree.  There is no way for the
function to notice that the default has changed with current
infrastructure, until we have the plan-dependency stuff in.

If this really harms you, you could use EXECUTE.  Or reconnect after you
change the table, whatever.

create or replace function insert_bugtest (
    vname text )
returns int as $f$
begin
    execute $e$ insert into bugtest ( name ) values
        ($e$ || quote_literal(vname) || $e$) $e$;
    return currval('bugtest_id_seq');
end; $f$ language plpgsql security definer;


--
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.