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A 5.5 version of the fix for Bug #54360 "Deadlock DROP/ALTER/CREATE

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DATABASE with open HANDLER"

Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.

Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)

By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".

The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().

This patch also adds a simple template to help work with 
the mysys HASH data structure.

Most of the patch was written by Konstantin Osipov.
This commit is contained in:
Jon Olav Hauglid
2010-07-01 15:53:46 +02:00
parent 29e9130d60
commit 9ff272fbbd
28 changed files with 1300 additions and 652 deletions
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23
sql/sql_help.cc
View File

@ -643,23 +643,24 @@ bool mysqld_help(THD *thd, const char *mask)
MEM_ROOT *mem_root= thd->mem_root;
DBUG_ENTER("mysqld_help");
bzero((uchar*)tables,sizeof(tables));
tables[0].alias= tables[0].table_name= (char*) "help_topic";
tables[0].lock_type= TL_READ;
tables[0].init_one_table(C_STRING_WITH_LEN("mysql"),
C_STRING_WITH_LEN("help_topic"),
"help_topic", TL_READ);
tables[1].init_one_table(C_STRING_WITH_LEN("mysql"),
C_STRING_WITH_LEN("help_category"),
"help_category", TL_READ);
tables[2].init_one_table(C_STRING_WITH_LEN("mysql"),
C_STRING_WITH_LEN("help_relation"),
"help_relation", TL_READ);
tables[3].init_one_table(C_STRING_WITH_LEN("mysql"),
C_STRING_WITH_LEN("help_keyword"),
"help_keyword", TL_READ);
tables[0].next_global= tables[0].next_local=
tables[0].next_name_resolution_table= &tables[1];
tables[1].alias= tables[1].table_name= (char*) "help_category";
tables[1].lock_type= TL_READ;
tables[1].next_global= tables[1].next_local=
tables[1].next_name_resolution_table= &tables[2];
tables[2].alias= tables[2].table_name= (char*) "help_relation";
tables[2].lock_type= TL_READ;
tables[2].next_global= tables[2].next_local=
tables[2].next_name_resolution_table= &tables[3];
tables[3].alias= tables[3].table_name= (char*) "help_keyword";
tables[3].lock_type= TL_READ;
tables[0].db= tables[1].db= tables[2].db= tables[3].db= (char*) "mysql";
init_mdl_requests(tables);
/*
HELP must be available under LOCK TABLES.