Reg Me Please wrote:
Sorry but I don't understand.
Either the LIMIT and OFFSET are to be definitely CONSTANT or not.
They must be constant during the execution of the query.
In the SQL function body the LIMIT and the OFFSET *are definitely not*
CONSTANT. And the planner can do its job at best as usual.
Well, they're constant during one execution of the query, but I grant
you the planner doesn't know what values they will have.
As Sam says I should be able to "put an IMMUTABLE expression into a LIMIT or
OFFSET". And under some circumstances (SQL function body) it's true even with
VARIABLE expressions like function call arguments.
And you can.
CREATE FUNCTION limfunc() RETURNS integer AS 'SELECT 2' LANGUAGE SQL
IMMUTABLE;
SELECT * FROM fit LIMIT limfunc();
a | b
---+----
1 | 43
2 | 43
(2 rows)
In my opinion I would say it's more a problem with the syntax checker that
with the planner ("semantics" in my lingo). But I could be wrong.
Well, what it won't let you do is have a subquery in the LIMIT clause.
That's probably due to a combination of:
1. The spec probably says something about it
2. There is an obvious approach involving functions/prepared queries
3. You're the first person to have asked for it.
Now if you can get a couple of hundred to join you at #3, you might have
a feature request :-)
--
Richard Huxton
Archonet Ltd
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