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Fix for:

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Bug #20662 "Infinite loop in CREATE TABLE IF NOT EXISTS ... SELECT
              with locked tables"
  Bug #20903 "Crash when using CREATE TABLE .. SELECT and triggers"
  Bug #24738 "CREATE TABLE ... SELECT is not isolated properly"
  Bug #24508 "Inconsistent results of CREATE TABLE ... SELECT when
              temporary table exists"

Deadlock occured when one tried to execute CREATE TABLE IF NOT
EXISTS ... SELECT statement under LOCK TABLES which held
read lock on target table.
Attempt to execute the same statement for already existing
target table with triggers caused server crashes.
Also concurrent execution of CREATE TABLE ... SELECT statement
and other statements involving target table suffered from
various races (some of which might've led to deadlocks).
Finally, attempt to execute CREATE TABLE ... SELECT in case
when a temporary table with same name was already present
led to the insertion of data into this temporary table and
creation of empty non-temporary table.
 
All above problems stemmed from the old implementation of CREATE
TABLE ... SELECT in which we created, opened and locked target
table without any special protection in a separate step and not
with the rest of tables used by this statement.
This underminded deadlock-avoidance approach used in server
and created window for races. It also excluded target table
from prelocking causing problems with trigger execution.

The patch solves these problems by implementing new approach to
handling of CREATE TABLE ... SELECT for base tables.
We try to open and lock table to be created at the same time as
the rest of tables used by this statement. If such table does not
exist at this moment we create and place in the table cache special
placeholder for it which prevents its creation or any other usage
by other threads.
We still use old approach for creation of temporary tables.

Note that we have separate fix for 5.0 since there we use slightly
different less intrusive approach.
This commit is contained in:
dlenev@mockturtle.local
2007-05-11 21:51:03 +04:00
parent 770219c15a
commit 4cafc8eeec
17 changed files with 1465 additions and 245 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
sql/sql_parse.cc
View File

@ -2164,7 +2164,13 @@ mysql_execute_command(THD *thd)
select_lex->options|= SELECT_NO_UNLOCK;
unit->set_limit(select_lex);
if (!(res= open_and_lock_tables(thd, select_tables)))
if (!(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
{
lex->link_first_table_back(create_table, link_to_local);
create_table->create= TRUE;
}
if (!(res= open_and_lock_tables(thd, lex->query_tables)))
{
/*
Is table which we are changing used somewhere in other parts
@ -2173,6 +2179,7 @@ mysql_execute_command(THD *thd)
if (!(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
{
TABLE_LIST *duplicate;
create_table= lex->unlink_first_table(&link_to_local);
if ((duplicate= unique_table(thd, create_table, select_tables, 0)))
{
update_non_unique_table_error(create_table, "CREATE", duplicate);
@ -2198,6 +2205,12 @@ mysql_execute_command(THD *thd)
}
}
/*
FIXME Temporary hack which will go away once Kostja pushes
his uber-fix for ALTER/CREATE TABLE.
*/
lex->create_info.table_existed= 0;
if ((result= new select_create(create_table,
&lex->create_info,
lex->create_list,
@ -2217,6 +2230,9 @@ mysql_execute_command(THD *thd)
lex->create_list.empty();
lex->key_list.empty();
}
else if (!(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
create_table= lex->unlink_first_table(&link_to_local);
}
else
{