From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
Cc: | Reece Hart <reece(at)harts(dot)net>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: text column indexing in UTF-8 database |
Date: | 2009-03-13 17:13:10 |
Message-ID: | 12217.1236964390@sss.pgh.pa.us |
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Lists: | pgsql-general |
Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> It looks like an index using text_pattern_ops can be used for equality
> (see my test case below).
This is true as of 8.4; prior versions make a distinction between =
and ~=~.
> This works apparently because texteq() is defined as bitwise-equality.
> Is that really correct? I was under the impression that some locales do
> not obey that rule, and may consider two slightly different strings to
> be equal.
The locale might, but Postgres doesn't --- look at the implementation
of texteq().
There is actually some history here; the former distinction in the
equality operators arose from exactly your concern. But after we
put in the second-pass check to insist on bitwise equality, we
realized that the equality operators really were equivalent.
regards, tom lane
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