Re: string_to_array with an empty input string

On Wed, Aug 11, 2010 at 10:32 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Greg Stark <gsstark@mit.edu> writes:
>> Ideally you really want string_to_array(array_to_string(x, ':'),':')
>> to return x. There's no safe return value to pick for the cases where
>> x=[''] and x=[] that will make this work.
>
> It's easy to see that string_to_array/array_to_string are *not* usable
> as general-purpose serialize/deserialize operations, so sweating over
> corner cases like this one seems a bit pointless.  The design center
> for 'em seems to be array elements that are numbers, so there's no
> issue with empty strings and no great difficulty in picking delimiters
> and null representations that can't appear in the data.  I think they're
> essentially worthless for arrays of text.

array_to_string() is quite useful for arrays of text; I use it to
generate human-readable output, by setting the delimiter to ', '.

Whether string_to_array() is useful is another matter.  It probably is
in some cases, but putting parsing logic into the database layer tends
to be a bit klunky, unless you know from context that you needn't
worry about the error cases.

--
Robert Haas
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