Tom Lane wrote:
I'm starting to vacillate again. It's clear that for the purposes
of string_to_array, an empty input string is fundamentally ambiguous:
it could mean a list of no things, or a list of one empty thing.
Agreed. Of the two, a list of one empty thing makes string_to_array
closer to an inverse of array_to_string.
Or we could stick to the current behavior and say "use COALESCE() to
resolve the ambiguity, if you need to".
Currently string_to_array(null, ',') yields a null result -
indistinguishable from string_to_array('',','). Wrapping in coalesce
does not help distinguish true null input from empty-string input. I'm
not sure at the moment what other cases exist where non-null input
generates null output.
If the decision is to leave the behavior unchanged, it at least cries
out for a documentation patch.
Cheers,
Steve
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