[HACKERS] RFC: Query Planner making a distinction between Cross Database and Cross Schema ?

[Stef]

Hey there everyone.

Sorry for what seems to be a rather strange
thought but, could we change the seperator used to
distinguish 'cross-database' vs 'cross-schema' ?

For example, i would expect the following
to work:

CREATE OR REPLACE FUNCTION test_autohist() RETURNS trigger
AS 'BEGIN
INSERT INTO history.test2 VALUES 
(new.field1,history.test_hist.nextval(), new.field2, new.field3, new.field4, 
new.creation_id, new.creation_date, new.creation_id, new.creation_date);
RETURN ;
END;' LANGUAGE 'plpgsql';
 
CREATE TRIGGER test_autohist_trig
AFTER INSERT OR UPDATE ON test
FOR EACH ROW
EXECUTE PROCEDURE test_autohist();


However, when i try it, as far as i can tell,
the planner parses it down, finds that the schema isnt
in the current 'search_path' and thus thinks its a cross
database call.

I understand that it may take the planner a 
while to go through all the available schema's to then
deduce that it isnt infact a schema at all and return
the fact that 'cross-database queries are currently not
implemented', therefore, in the realm of crazy idea, 
would it be possible to change the notation to reference
another db ?

I was thinking something along the lines of '@',
but i guess any other non-important ascii character would
make sense.

That way, the planner could decide wether or not
to attempt a schema resolution (history.table1) or database
resolution ([EMAIL PROTECTED]).


Please note, i am not asking for any sort of 
'make cross-database work', merely asking if some sort
of 'clarification' between cross-database and cross-schema
would be beneficial. 

Ideas ? Comments ? 

regards
Stef

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Re: [HACKERS] RFC: Query Planner making a distinction between Cross Database and Cross Schema ?

[Stef]

 U.  Postgresql doesn't natively support cross database queries...
 

I know, but it does schema's, and currently, the same
notation is used to specify schema's as 'cross database'.

So the planner often reports 'cross-database not allowed'
in areas where it should at least report 'cross-schema
support is unavailable for this'

case in point, the example trigger. i would have expected
deliberate schemaname.table during an insert to work, but
instead the parser complains about cross-database.

this is why i am saying that if the parser could identify
schema vs database naming, it would help in clarification
of areas where the parser/planner seems to get 'confused'
about what the object is (schema vs database)

currently:  history.table1   -- schema
history2.table1  -- database

whereas what i am saying is:
history.table1   -- schema
[EMAIL PROTECTED]  -- database


readability and consistancy is what i am driving at
here, although it would then be possible for the triggers
to be able to insert/update into schema's that are
specifically named instead of coming back with a 
'cross-database not allowed' (when i am trying
to do cross-schema :)


regards
Stef

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Re: [HACKERS] RFC: Query Planner making a distinction between Cross Database and Cross Schema ?

[Stef]

  case in point, the example trigger. i would have expected
  deliberate schemaname.table during an insert to work, but
  instead the parser complains about cross-database.
 
 I would think just changing the error message to no schema by the name of 
 suchandsuch found would make it pretty clear.
 

indeed, the only problem being, that this is a 
-deliberately- called schema and it does exist
jst that its not in the search_path. surely the
pl/pglsql or parser should be able to search the
schemanames if i give it a -deliberate- name and
if it isnt there say 'not found' ?

so, either thats an error (improper parsing/expr
forming) in the pl/pgsql trigger code, or, well,
i dont know. 

thoughts ? comments ? barking mad ?
Stef

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Re: [HACKERS] RFC: Query Planner making a distinction between Cross Database and Cross Schema ?

[Tom Lane]

Stef [EMAIL PROTECTED] writes:
   For example, i would expect the following
 to work:

   CREATE OR REPLACE FUNCTION test_autohist() RETURNS trigger
   AS 'BEGIN
   INSERT INTO history.test2 VALUES 
 (new.field1,history.test_hist.nextval(), new.field2, new.field3, new.field4, 
 new.creation_id, new.creation_date, new.creation_id, new.creation_date);

Why would you expect that to work?

The problem is with this bit:
history.test_hist.nextval()
which is a cross-database function reference per the standard SQL syntax
for such things.  (If you were in the history database, it wouldn't be
cross-database, but would refer to the nextval() function in the local
test_hist schema.)

I am not sure what you meant here, but I cannot see any need to
introduce a nonstandard syntax to resolve it.

regards, tom lane

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