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Re: [QUESTIONS] varchar vs text

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: lockhart(at)alumni(dot)caltech(dot)edu (Thomas G(dot) Lockhart)
Cc: Daniel(dot)Brickley(at)Bristol(dot)ac(dot)uk, hackers(at)postgresql(dot)org
Subject: Re: [QUESTIONS] varchar vs text
Date: 1998-03-01 21:39:28
Message-ID: 199803012139.QAA26843@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
> 
> > > > Varchar currently (in 6.2.1 and below) takes up the entire length specified
> > > > in the definition, despite the fact the value in it may actually be
> > > > shorter. Text takes only the space taken by the value.
> > >
> > > Thanks for the clarification. In this case, what happens with varchar's
> > > length if the original definition for that field leaves length undefined?
> > > Does it behave like text in that case?
> >
> > You really shouldn't be doing that.  Not sure what happens.  Not a good
> > idea:
> >
> >         create table test (x varchar);
> 
> ?? This was defined to be a varchar of unlimited length, much like, or identical
> to, text. Should this now be disallowed? If so, we can fix the parser to disallow
> it so people don't get misled.

Oh, I didn't know.  There really is no difference between varchar with
no lenght, and text, but if it doesn't break anything, no problem.

> 
> > > I also vaguely recall seeing a message last year about the use of indexes
> > > in queries: that in [some circumstances] indexes built on varchar fields
> > > don't get used and a sequential scan through all records takes place
> > > instead. Is there any distinction between varchar and text here?
> >
> > Don't remember that.
> 
> This was probably Bruce's improvements to allow indices on some pattern matching.
> Doesn't make a distinction between these types in its behavior.

Not sure what to say on this.  I remember that issue, but not how it
caused any problem.

-- 
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