Ken Benson <Ken@infowerks.com> writes:
> On Sun, Nov 12, 2017 at 2:34 PM, Tom Lane <tgl@sss.pgh.pa.us<mailto:tgl@sss.pgh.pa.us>> wrote:
> Generally speaking, I would only use varchar(n) when there is a clear
> reason traceable to application requirements why there has to be a
> limit, and why the limit should be n and not some other number.
> Is this true – even if the column in question will be used in (or as part of) an INDEX.
> It seems to be the index would work best if the length of the columns involved is a known value.
varchar(n) doesn't have a known length. Even char(n) doesn't have a known
length in the presence of variable-width text encodings. So there are no
optimizations of the sort you're imagining in Postgres.
regards, tom lane
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