On 10/08/2013 12:30 PM, Robert Haas wrote:
On Tue, Oct 8, 2013 at 8:33 AM, Andrew Dunstan <and...@dunslane.net> wrote:
On 10/07/2013 11:34 PM, Amit Kapila wrote:
On Tue, Oct 8, 2013 at 12:55 AM, Andrew Dunstan <and...@dunslane.net>
wrote:
On 10/07/2013 03:06 PM, Robert Haas wrote:
Also if your use case is to treat empty strings as NULL (as per above
documentation), can't it be handled with "WITH NULL AS" option.
For example, something like:
postgres=# COPY testnull FROM stdin with CSV NULL AS E'';
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
50,
\.
postgres=# select * from testnull;
a | b
----+------
50 | NULL
(1 row)
Good point. If this patch is just implementing something that can
already be done with another syntax, we don't need it.
Isn't the point of this option to allow a *quoted* empty string to be
forced
to NULL? If so, this is not testing the same case - in fact the COPY
command
above just makes explicit the default CSV NULL setting anyway.
I am really not sure if all the purpose of patch can be achieved by
existing syntax, neither it is explained clearly.
However the proposal hasn't discussed why it's not good idea to extend
some similar syntax "COPY .. NULL" which is used to replace string
with NULL's?
Description of NULL says: "Specifies the string that represents a null
value."
Now why can't this syntax be extended to support quoted empty string
if it's not supported currently?
I have not checked completely, If it's difficult or not possible to
support in existing syntax, then even it add's more value to introduce
new syntax.
By asking above question, I doesn't mean that we should not go for the
new proposed syntax, rather it's to know and understand the benefit of
new syntax, also it helps during CF review for reviewer's if the
proposal involves new syntax and that's discussed previously.
Quite apart from any other consideration, this suggestion is inferior to
what's proposed in that it's an all or nothing deal, while the patch allows
you to specify the behaviour very explicitly on a per column basis. I can
well imagine wanting to be able to force a quoted empty string to null for
numeric fields but not for text.
The basic principal of our CSV processing is that we don't ever turn a NULL
into something quoted and we don't ever turn something quoted into NULL.
That's what lets us round-trip test just about every combination of options.
I'm only going to be happy violating that, as this patch does, in a very
explicit and controlled way.
Andrew, are you planning to review & commit this?
Yes.
cheers
andrew
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