On 12/26/2014 05:18 AM, Andreas Ulbrich wrote:
On 25.12.2014 23:50, Adrian Klaver wrote:
On 12/25/2014 11:21 AM, Andreas Ulbrich wrote:
Hey.
In the first part I connect to testdb (the remote db). Here I create the
schema 'andreas'. That the search_path correct is, shows the output of
the pgplsql version.
Yeah, that was a false alarm on my part. Forgot about $user in the path.
Then, in the second part, I'm postgres (this db ist empty since
compiling).
The usermapping says, I wont to be andreas@testdb.
The plpgsql-version (and the other work arround: schema qualified, set
search_path) shows, that my assumptions are correct.
First I'm wondering, why are the constraints are checked in select, but
this is not the main problem, because, if I would do an INSERT, I will
get the same problem.
The issue seems to begin here:
CREATE TABLE IF NOT EXISTS tab_b (
id INTEGER PRIMARY KEY,
id_a INTEGER NOT NULL REFERENCES tab_a,
name TEXT,
CHECK(test_name_b(id_a, name))
);
The CHECK calls test_name_b() which has
SELECT $2 = name FROM tab_a WHERE id = $1 in it
As Tom said fdw calls have a limited search_path and the tab_b table
is not schema qualified in the function, so:
2014-12-24 13:11:27 CET andreas(at)testdb QUERY: SELECT $2 = name FROM
tab_a WHERE id = $1
2014-12-24 13:11:27 CET postgres(at)postgres ERROR: relation "tab_a"
does
not exist
2014-12-24 13:11:27 CET postgres(at)postgres CONTEXT: Remote SQL
command:
SELECT id, id_a, name FROM andreas.tab_b
SQL function "test_name_b" during inlining
As you found out you need to be explicit about your schemas when going
through fdw. Either schema qualify object names of set explicit
search_path,
All this starts when you try to create the foreign table:
2014-12-24 13:11:27 CET postgres(at)postgres STATEMENT: TABLE ftab_b;
I believe, that the "inlining" does not use the search_path set in the
ALTER DATABASE.
Here is a \d output before the END of the transaction in the first part.
List of relations
Schema | Name | Type | Owner
---------+----------+---------------+---------
andreas | tab_a | table | andreas
andreas | tab_b | table | andreas
test | unaccent | foreign table | test
Regards
Andreas
O.K. I've seen.
I tried again the plpgsql version:
1.) the INSERTS on testdb prints the correct search_path in the raise
WARNING: test_name_b called: "$user", test, public, ext
2.) Here the TABLE ftab_B works; because the check constraint is not
done (the constraint function is not called)
Is there any deeper cause, why the check is done with SQL function and
not with plpgsql in SELECT? It seems not necessary to do the check - for
me.
This, from what I gather, is the result of the SQL inlining process
whereby SQL functions are optimized ahead of use. So the error shows up
when Postgres walks through the SQL function to do the optimization. In
the plpgsql function this does not happen. Someone with more knowledge
of the internals will have to fill in the details.
3.) Is I try to make an INSERT from postgres to testdb, it failes.
And here is the search path not set:
WARNING: test_name_b called: pg_catalog
The search_path is set, it is just very restricted.
I think, that's a gap in the fdw.
Well as Tom said in his post:
"Anyway, as far as your second question goes, the postgres_fdw wrapper
intentionally forces the search_path to be just "pg_catalog" in its
remote session. We're aware that this breaks carelessly written
triggers and CHECK functions and so on, but really such functions
are broken anyhow; they should not be assuming anything about what
search_path they're called with.
"
My idea was the following: I wont do some refactoring. So a created a
new DB with a new schema with the refactored data structure. To populate
this new structure I wanted to use fdw-select to the old structure. The
problem is, I can't do so much changes in the old structure. Further,
qualified table access in the function makes them not reuseable in the
new structure.
O.K. the new idea is. Create a new 'export' schema in the old DB with a
constraintless export formated tables (JSON), populate this in the old
DB and then use fdw to these special designed tables.
Well fdw is not the only game in town, there is also dblink:
http://www.postgresql.org/docs/9.3/interactive/dblink.html
Thanks
Andreas
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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