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MDEV-7947 strcmp() takes 0.37% in OLTP RO

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This patch ensures that all identical character sets shares the same
cs->csname.
This allows us to replace strcmp() in my_charset_same() with comparisons
of pointers. This fixes a long standing performance issue that could cause
as strcmp() for every item sent trough the protocol class to the end user.

One consequence of this patch is that we don't allow one to add a character
definition in the Index.xml file that changes the csname of an existing
character set. This is by design as changing character set names of existing
ones is extremely dangerous, especially as some storage engines just records
character set numbers.

As we now have a hash over character set's csname, we can in the future
use that for faster access to a specific character set. This could be done
by changing the hash to non unique and use the hash to find the next
character set with same csname.
This commit is contained in:
Monty
2020-07-20 19:26:31 +03:00
parent 46ffd47f42
commit dbcd3384e0
30 changed files with 386 additions and 245 deletions
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5
mysql-test/suite/innodb/r/innodb_ctype_ldml.result
View File

@@ -383,7 +383,7 @@ Bug#46448 trailing spaces are not ignored when user collation maps space != 0x20
set names latin1;
show collation like 'latin1_test';
Collation Charset Id Default Compiled Sortlen
latin1_test latin1 99 Yes 1
latin1_test latin1 331 1
select "foo" = "foo " collate latin1_test;
"foo" = "foo " collate latin1_test
1
@@ -402,6 +402,7 @@ utf8mb4_test_ci utf8mb4 326 8
utf16_test_ci utf16 327 8
utf8mb4_test_400_ci utf8mb4 328 8
utf8mb4_test_520_nopad_ci utf8mb4 329 8
latin1_test latin1 331 1
latin1_test2 latin1 332 1
latin1_test2_cs latin1 333 1
latin1_swedish_nopad2_ci latin1 334 1
@@ -426,7 +427,7 @@ utf32_test_ci utf32 391 8
utf8_maxuserid_ci utf8 2047 8
show collation like '%test%';
Collation Charset Id Default Compiled Sortlen
latin1_test latin1 99 Yes 1
latin1_test latin1 331 1
latin1_test2 latin1 332 1
latin1_test2_cs latin1 333 1
utf8_test_ci utf8 353 8

1
mysql-test/suite/innodb/t/innodb_ctype_ldml.test
View File

@@ -13,6 +13,7 @@ drop table if exists t1;
--disable_query_log
call mtr.add_suppression("Syntax error at '\\[strength tertiary\\]'");
call mtr.add_suppression("Can't reset before a primary ignorable character U\\+A48C");
call mtr.add_suppression("Charset id.*trying to replace");
--enable_query_log
--echo In the following tests we change the order of letter "b"