BUG #3628: Wrong schema picked
The following bug has been logged online:
Bug reference: 3628
Logged by: Pedro Gimeno
Email address: pgsql-001@personal.formauri.es
PostgreSQL version: 8.2.4
Operating system: Linux (Debian stable + backports)
Description: Wrong schema picked
Details:
When a function has a SQL statement to execute that has an unqualified
table, that SQL statement doesn't always pick the table from a schema in the
search_path. The following script is an example:
-- begin script
create database test2;
\c test2
create language 'plpgsql';
create schema schema1;
create schema schema2;
create table schema1.table1 (column1 varchar(10));
create table schema2.table1 (column1 varchar(10));
create function public.f1() returns void as $$
begin
insert into table1 values (current_schema());
end;
$$ language plpgsql;
set search_path=schema1,public;
select f1();
set search_path=schema2,public;
select f1();
select * from schema1.table1;
select * from schema2.table1;
-- end script
The output of the last couple of SELECT statements is:
column1
---------
schema1
schema2
(2 rows)
column1
---------
(0 rows)
while the expected result would be:
column1
---------
schema1
(1 row)
column1
---------
schema2
(1 row)
-- Pedro Gimeno
Pedro Gimeno wrote:
When a function has a SQL statement to execute that has an unqualified
table, that SQL statement doesn't always pick the table from a schema in the
search_path.
The first time the function is run, all the statements in it are planned
and the schema used for the insert is resolved. Subsequent calls will
reuse the same plan. The obvious fix is to always explicitly specify the
schema in the INSERT. Or if if you want it to depend on the search_path,
you can execute it dynamically using EXECUTE
(http://www.postgresql.org/docs/8.2/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN).
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
Heikki Linnakangas wrote:
Pedro Gimeno wrote:
When a function has a SQL statement to execute that has an
unqualified table, that SQL statement doesn't always pick the table
from a schema in the search_path.The first time the function is run, all the statements in it are
planned and the schema used for the insert is resolved. Subsequent
calls will reuse the same plan. The obvious fix is to always
explicitly specify the schema in the INSERT. Or if if you want it to
depend on the search_path, you can execute it dynamically using
EXECUTE
(http://www.postgresql.org/docs/8.2/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN).
That's the workaround I'm using, yet I find this behaviour quite
unexpected. Using EXECUTE prevents the benefit of using prepared
statements until search_path changes or a schema is deleted or renamed,
not to mention the impact on readability.
What I expect is that when search_path changes, either explicitly or
implicitly (e.g. by creating a temporary table), or a schema is deleted
or renamed, the affected prepared queries are parsed again so that the
right schema is picked.
This would allow using a common schema for functions instead of
defining them once in every schema in which to apply them, in cases
(like mine) where the same operations have to be applied to different
schemas.
-- Pedro Gimeno
Heikki Linnakangas wrote:
The first time the function is run, all the statements in it are
planned and the schema used for the insert is resolved. Subsequent
calls will reuse the same plan.
This post is apparently related:
http://archives.postgresql.org/pgsql-hackers/2007-02/msg00933.php
-- Pedro Gimeno