| From: | Bruce Hyatt <brucejhyatt(at)yahoo(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Aurynn Shaw <ashaw(at)commandprompt(dot)com>, "Don Mies \(NIM\)" <dmies(at)networksinmotion(dot)com>, pgsql-novice(at)postgresql(dot)org |
| Subject: | Re: Disadvantages to using "text" |
| Date: | 2008-05-08 01:40:52 |
| Message-ID: | 694890.72880.qm@web34405.mail.mud.yahoo.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-novice |
> Well, all the textual operators/functions are actually
> declared to take
> and return type TEXT, so when you are working with VARCHAR
> columns the
> expressions have no-op cast nodes in them ("RelabelType"
> nodes), even
> if it's an unconstrained-length VARCHAR. I'm not sure whether
> the
> execution cost of these would be measurable in real
> applications, but
> it's not zero. A bigger problem is that sometimes the planner
> gets
> confused by the RelabelTypes and fails to find as good a plan
> as it
> finds for a pure-TEXT query.
I assume this is true for version 7 as well as version 8.
Bruce
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