Re: [QUESTIONS] varchar vs text

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От Thomas G. Lockhart
Тема Re: [QUESTIONS] varchar vs text
Дата
Msg-id 34F9D317.DB96E2A7@alumni.caltech.edu
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Ответы Re: [QUESTIONS] varchar vs text  (Bruce Momjian <maillist@candle.pha.pa.us>)
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> > > 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.

> > 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.

                                                  - Tom


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