Hi,
...
> In researching a problem I have uncovered the following bug in index
> scans when Locale support is enabled.
...
> environment variable is set to en_US) to enable the US english locale
...
> create table test (test_col text);
> create index test_index on test (test_col);
> insert into test values ('abc.xyz');
> insert into test values ('abcxyz');
> insert into test values ('abc/xyz');
>
> If you run the query:
>
> select * from test where test_col >= 'abc.';
>
> One would normally expect to only get one record returned, but instead
> all records are returned.
I would expect all to be returned (maybe not "abc/..."). Because noice
should be sorted first. ie. '.' is less than '0' and 'x' (and maybe '/').
...
> The reason for this is that in the en_US locale all non-alphanumeric
> characters are ignored when doing string comparisons. So the data above
...or... *I think* they are sorted first. If that is correct in your locale,
I do not know.
...
> Note that if you use a different locale for example en_UK, you will get
Thats odd, I would expect en_UK and en_US to sort the same way (same
charset).
...
> select * from text where test_col like 'abc/%';
>
> This query should return one row, the row for 'abc/xyz'. However if the
> above query is executed via an index scan it will return the wrong
> number of rows (0 in this case).
ehh index scan? test_col >= 'abc/' or test_col >= 'abc/%' ????
The first one should return all rows but the one with '.', while the second
should return 0 rows. If the first one returns zero rows, then its a bug.
If you meant what the optimizer does with LIKE, well *I think* such
optimazion is asking for trouble (compare strings with anything else than =
and != are, well hard to predict).
...
> "like '/aaa/bbb/%' don't work. From the above information I have
> determined that such queries don't work if:
> a) database is built with Locale support enabled (--enable-locale)
Actually they should not work without '--enable-locale', or then Im wrong.
> b) the database is running with locale en_US
> c) the column the like is being performed on is indexed
Dangerous LIKE optimation.
...
> The current implementation for converting the like into an index scan
> doesn't work with Locale support enabled and the en_US locale as shown
Hmm. If memory serves its dropped in the later builds (no like optimation).
// Jarmo
