Hello,
Alexander Barkov a écrit, Le 28.04.2010 14:13:
> #At file:///home/bar/mysql-bzr/mysql-trunk-bugfixing/ based on
> revid:dao-gang.qu@stripped
>
> 3025 Alexander Barkov 2010-04-28
> Bug#52849 [Com]: datetime index not work
> Problem: after introduction of "WL#2649 Number-to-string conversions"
>
> This query:
> SET NAMES cp850; -- Or any other non-latin1 ASCII-based character set
> SELECT * FROM t1
> WHERE datetime_column='2010-01-01 00:00:00'
> started to add extra character set conversion:
> SELECT * FROM t1
> WHERE CONVERT(datetime_column USING cp850)='2010-01-01 00:00:00';
>
> so index on DATETIME column was not used anymore.
>
> Fix:
> avoid convertion of NUMERIC/DATETIME items
> (i.e. those with derivation DERIVATION_NUMERIC).
>
> modified:
> mysql-test/r/type_datetime.result
> mysql-test/t/type_datetime.test
> sql/item.cc
I'm reviewing this but being quite ignorant of the concepts here, I have
only questions so far.
> === modified file 'sql/item.cc'
> --- a/sql/item.cc 2010-04-19 08:27:46 +0000
> +++ b/sql/item.cc 2010-04-28 12:04:20 +0000
> @@ -1796,6 +1796,20 @@ bool agg_item_set_converter(DTCollation
> &dummy_offset))
> continue;
>
> + /*
> + No needs to add converter if an "arg" is NUMERIC or DATETIME
> + value (which is pure ASCII) and at the same time target DTCollation
> + is ASCII-compatible. For example, no needs to rewrite:
> + SELECT * FROM t1 WHERE datetime_field = '2010-01-01';
> + to
> + SELECT * FROM t1 WHERE CONVERT(datetime_field USING cs) = '2010-01-01';
> + */
> + if ((*arg)->collation.derivation == DERIVATION_NUMERIC &&
> + (*arg)->collation.repertoire == MY_REPERTOIRE_ASCII &&
is this test needed? Isn't the first one (about derivations) enough?
What is a repertoire (ok it's a French word but what does it mean here
;-)? What does MY_REPERTOIRE_ASCII mean?
There exists MY_REPERTOIRE_NUMERIC, should it be used instead?
> + !((*arg)->collation.collation->state & MY_CS_NONASCII) &&
a member named "collation" in an object named "collation"
(collation.collation) - what is it about?
I have the impression that the 3 first tests are about the number/date's
collation? do we need to test all three?
> + !(coll.collation->state & MY_CS_NONASCII))
this one is about the target collation it seems.
Can't the entire if() just be:
if !((*arg)->collation.collation->state & MY_CS_NONASCII) &&
!(coll.collation->state & MY_CS_NONASCII))
{
//it's all ASCII
continue;
}
I guess no, but why?
> + continue;
> +
> if (!(conv= (*arg)->safe_charset_converter(coll.collation)) &&
> ((*arg)->collation.repertoire == MY_REPERTOIRE_ASCII))
> conv= new Item_func_conv_charset(*arg, coll.collation, 1);
Thanks!
--
Mr. Guilhem Bichot <guilhem@stripped>
Sun Microsystems / MySQL, Lead Software Engineer
Bordeaux, France
www.sun.com / www.mysql.com
