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MDEV-25829 Change default Unicode collation to uca1400_ai_ci

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Step#1 - Changing collation derivation for string user variables
from IMPLICIT to COERCIBLE.

Retionale:

Without this preparatory change, switching the default collation for
Unicode character sets from xxx_general_ci to uca1400_ai_ci would cause
"Illegal mix of collations" errors in scenarios comparing a column with
a non-default collation to a string user variable

This is especially important for queries to INFORMATION_SCHEMA tables,
whose columns use utf8mb3_general_ci.

See the description of MDEV-25829 for more details and SQL script examples.
This commit is contained in:
Alexander Barkov
2023-11-15 06:09:41 +04:00
parent 44974a0788
commit 1b65cc9da7
5 changed files with 33 additions and 16 deletions
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14
mysql-test/main/user_var.result
View File

@ -137,7 +137,7 @@ drop table t1;
set @a=_latin2'test';
select charset(@a),collation(@a),coercibility(@a);
charset(@a) collation(@a) coercibility(@a)
latin2 latin2_general_ci 2
latin2 latin2_general_ci 4
select @a=_latin2'TEST';
@a=_latin2'TEST'
1
@ -147,7 +147,7 @@ select @a=_latin2'TEST' collate latin2_bin;
set @a=_latin2'test' collate latin2_general_ci;
select charset(@a),collation(@a),coercibility(@a);
charset(@a) collation(@a) coercibility(@a)
latin2 latin2_general_ci 2
latin2 latin2_general_ci 4
select @a=_latin2'TEST';
@a=_latin2'TEST'
1
@ -162,19 +162,19 @@ collation(@a:=_latin2'test')
latin2_general_ci
select coercibility(@a:=_latin2'test');
coercibility(@a:=_latin2'test')
2
4
select collation(@a:=_latin2'test' collate latin2_bin);
collation(@a:=_latin2'test' collate latin2_bin)
latin2_bin
select coercibility(@a:=_latin2'test' collate latin2_bin);
coercibility(@a:=_latin2'test' collate latin2_bin)
2
4
select (@a:=_latin2'test' collate latin2_bin) = _latin2'TEST';
(@a:=_latin2'test' collate latin2_bin) = _latin2'TEST'
0
select charset(@a),collation(@a),coercibility(@a);
charset(@a) collation(@a) coercibility(@a)
latin2 latin2_bin 2
latin2 latin2_bin 4
select (@a:=_latin2'test' collate latin2_bin) = _latin2'TEST' collate latin2_general_ci;
(@a:=_latin2'test' collate latin2_bin) = _latin2'TEST' collate latin2_general_ci
1
@ -184,11 +184,11 @@ my_column
0
select @v, coercibility(@v);
@v coercibility(@v)
NULL 2
NULL 4
set @v1=null, @v2=1, @v3=1.1, @v4=now();
select coercibility(@v1),coercibility(@v2),coercibility(@v3),coercibility(@v4);
coercibility(@v1) coercibility(@v2) coercibility(@v3) coercibility(@v4)
2 5 5 2
4 5 5 4
set session @honk=99;
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '@honk=99' at line 1
select @@local.max_allowed_packet;