From: | Brendan Jurd <direvus(at)gmail(dot)com> |
---|---|
To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: patch: to_string, to_array functions |
Date: | 2010-07-16 14:25:27 |
Message-ID: | AANLkTilErHj70iAqB238IbpQsKB2m20qvHaOioqxwfeG@mail.gmail.com |
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Lists: | pgsql-hackers |
On 6 May 2010 04:42, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> attached patch contains to_string and to_array functions. These
> functions are equivalent of array_to_string and string_to_array
> function with maybe more correct NULL handling.
Hi Pavel,
I am reviewing your patch for the commitfest.
Overall the patch looks good, although there were some bogus
whitespace changes in the patch and some messy punctuation/grammar in
some of the code comments. I also thought it was worth mentioning in
the docs the default value for null_string is ''. I made an attempt
to clean those items up and have attached a v2 of the patch.
Regarding the behaviour of the third argument (null_string), I was a
little surprised by the results when I passed in a NULL.
postgres=# select to_string(array['a', 'b', 'c', 'd'], '/', NULL);
to_string
-----------
Now, if the array had some NULL elements in it, I could understand why
the resulting string would be NULL (because str || NULL is NULL), but
in this case there are no NULLs. Why is the result NULL? Surely it
should be 'a/b/c/d' regardless of how the third parameter is set?
In the reverse case:
postgres=# select to_array('a/b/c/d', '/', NULL);
to_array
----------
(1 row)
Again I find this a bit weird. I have left the null_string NULL,
which means it is unknown. It can't possibly match any value in the
string, so effectively passing in a NULL null_string should mean that
the user doesn't want any string items whatsoever to translate into
NULLs in the resulting array. I would expect this call to return
{a,b,c,d}.
Cheers,
BJ
Attachment | Content-Type | Size |
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to_array-v2.diff | text/plain | 13.7 KB |
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