BUG #17456: pg_dump creates dump that does not fully respect operator schema location
The following bug has been logged on the website:
Bug reference: 17456
Logged by: Andrew Grossman
Email address: agrossman@gmail.com
PostgreSQL version: 14.2
Operating system: MacOS 12.3
Description:
I have a case where an AFTER ROW trigger has a condition comparing two ltree
fields. The ltree extension is installed in a different schema than the
triggered table is. Upon restoration, the following error is encountered:
psql:/tmp/bugreport.sql:93: ERROR: 42883: operator does not exist:
util.ltree = util.ltree
LINE 1: ...N my_schema.my_table FOR EACH ROW WHEN ((new.path IS DISTINC...
^
HINT: No operator matches the given name and argument types. You might need
to add explicit type casts.
LOCATION: op_error, parse_oper.c:731
The following sql will reproduce this case:
===================================
CREATE SCHEMA my_schema;
CREATE SCHEMA util;
CREATE EXTENSION ltree WITH SCHEMA util;
SET SEARCH_PATH=my_schema,util;
CREATE TABLE my_schema.my_table
(path ltree);
CREATE FUNCTION my_schema.noop() RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
RETURN NEW;
END;
$$;
CREATE TRIGGER path_update_after_trg
AFTER UPDATE ON my_schema.my_table
FOR EACH ROW WHEN ((new.path IS DISTINCT FROM old.path))
EXECUTE FUNCTION my_schema.noop();
===================================
end of reproduction setup sql.
Execution looks like:
===================================
createdb my_restore_db; pg_dump my_source_db | psql my_restore_db
...
CREATE TABLE
Time: 15.558 ms
ALTER TABLE
Time: 0.293 ms
COPY 0
Time: 0.216 ms
ERROR: 42883: operator does not exist: util.ltree = util.ltree
LINE 1: ...N my_schema.my_table FOR EACH ROW WHEN ((new.path IS DISTINC...
^
HINT: No operator matches the given name and argument types. You might need
to add explicit type casts.
LOCATION: op_error, parse_oper.c:731
Time: 3.546 ms
===============================
This is against server 13.6 with client 14.2.
My workaround for the current bug is to cast the comparison fields to text.
On Tue, Apr 5, 2022 at 8:31 AM PG Bug reporting form <noreply@postgresql.org>
wrote:
The following bug has been logged on the website:
Bug reference: 17456
Logged by: Andrew Grossman
Email address: agrossman@gmail.com
PostgreSQL version: 14.2
Operating system: MacOS 12.3
Description:I have a case where an AFTER ROW trigger has a condition comparing two
ltree
fields. The ltree extension is installed in a different schema than the
triggered table is. Upon restoration, the following error is encountered:psql:/tmp/bugreport.sql:93: ERROR: 42883: operator does not exist:
util.ltree = util.ltree
LINE 1: ...N my_schema.my_table FOR EACH ROW WHEN ((new.path IS DISTINC...
^
HINT: No operator matches the given name and argument types. You might
need
to add explicit type casts.
LOCATION: op_error, parse_oper.c:731The following sql will reproduce this case:
SET SEARCH_PATH=my_schema,util;
FOR EACH ROW WHEN ((new.path IS DISTINCT FROM old.path))
Yes, this is a known limitation extending from our securing the search_path
in order to fix a CVE.
Casting to text works since it will use the system pg_catalog.=(text,text)
operator.
The other option is to avoid the indirection caused by IS DISTINCT FROM and
write out the equivalent expression verbosely:
not(new.path operator("util"."=") old.path) OR (new.path IS NULL AND
old.path IS NULL)
Another option is to add a SET search_path clause on the CREATE FUNCTION
and move the WHEN check inside the function. When the trigger invokes the
function the attached search_path will then be put into force and the
resolution of =(lpath,lpath) will find the one in the util schema.
Unfortunately, the create trigger command doesn't have a similar capability
to attach a local setting value to it.
David J.
Ahh, that makes sense. Thank you for the thorough explanation. I wonder if
there's a good way to warn on this during the dump creation.
On Tue, Apr 5, 2022 at 12:05 PM David G. Johnston <
david.g.johnston@gmail.com> wrote:
Show quoted text
On Tue, Apr 5, 2022 at 8:31 AM PG Bug reporting form <
noreply@postgresql.org> wrote:The following bug has been logged on the website:
Bug reference: 17456
Logged by: Andrew Grossman
Email address: agrossman@gmail.com
PostgreSQL version: 14.2
Operating system: MacOS 12.3
Description:I have a case where an AFTER ROW trigger has a condition comparing two
ltree
fields. The ltree extension is installed in a different schema than the
triggered table is. Upon restoration, the following error is encountered:psql:/tmp/bugreport.sql:93: ERROR: 42883: operator does not exist:
util.ltree = util.ltree
LINE 1: ...N my_schema.my_table FOR EACH ROW WHEN ((new.path IS DISTINC...
^
HINT: No operator matches the given name and argument types. You might
need
to add explicit type casts.
LOCATION: op_error, parse_oper.c:731The following sql will reproduce this case:
SET SEARCH_PATH=my_schema,util;
FOR EACH ROW WHEN ((new.path IS DISTINCT FROM old.path))
Yes, this is a known limitation extending from our securing the
search_path in order to fix a CVE.Casting to text works since it will use the system pg_catalog.=(text,text)
operator.The other option is to avoid the indirection caused by IS DISTINCT FROM
and write out the equivalent expression verbosely:not(new.path operator("util"."=") old.path) OR (new.path IS NULL AND
old.path IS NULL)Another option is to add a SET search_path clause on the CREATE FUNCTION
and move the WHEN check inside the function. When the trigger invokes the
function the attached search_path will then be put into force and the
resolution of =(lpath,lpath) will find the one in the util schema.
Unfortunately, the create trigger command doesn't have a similar capability
to attach a local setting value to it.David J.