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Re: BUG #18467: postgres_fdw (deparser) ignores LimitOption - Mailing list pgsql-bugs

From Önder Kalacı
Subject Re: BUG #18467: postgres_fdw (deparser) ignores LimitOption
Date
Msg-id CACawEhVBz3Em2T9=Xe==n5xtHshs7+DQ7tUqN21TFE76tN4Arw@mail.gmail.com
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In response to Re: BUG #18467: postgres_fdw (deparser) ignores LimitOption  (Japin Li <japinli@hotmail.com>)
Responses Re: BUG #18467: postgres_fdw (deparser) ignores LimitOption
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Hi,

and 2) ORDER BY must already
> have been determined to be safe to push down before we get here.  

When I read the code, the decision for that seems to happen in the next line where this patch proposes to modify:

 /*
* Also, the LIMIT/OFFSET cannot be pushed down, if their expressions are
* not safe to remote.
*/
if (!is_foreign_expr(root, input_rel, (Expr *) parse->limitOffset) ||
!is_foreign_expr(root, input_rel, (Expr *) parse->limitCount))
return;
 
Hence, I thought it is OK to add this new check to this place.


 So
> in that case, if getting here, we can consider that WITH TIES is also
> safe to push down (if the remote is v13 or later). 

 See Tom's response here on why it might not be a good idea to pushdown

I think, at least not with this patch, this patch is like a bug-fix. If intended, it should be possible to
pushdown WITH TIES with a follow-up patch?

Thanks,
Onder


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