1SET @def_var= @@session.transaction_prealloc_size;
2SET SESSION transaction_prealloc_size=1024*1024*1024*1;
3SHOW PROCESSLIST;
4Id	User	Host	db	Command	Time	State	Info	Progress
5<Id>	root	<Host>	test	Query	<Time>	<State>	SHOW PROCESSLIST	0.000
6SET SESSION transaction_prealloc_size=1024*1024*1024*2;
7SHOW PROCESSLIST;
8Id	User	Host	db	Command	Time	State	Info	Progress
9<Id>	root	<Host>	test	Query	<Time>	<State>	SHOW PROCESSLIST	0.000
10SET SESSION transaction_prealloc_size=1024*1024*1024*3;
11SHOW PROCESSLIST;
12Id	User	Host	db	Command	Time	State	Info	Progress
13<Id>	root	<Host>	test	Query	<Time>	<State>	SHOW PROCESSLIST	0.000
14SET SESSION transaction_prealloc_size=1024*1024*1024*4;
15SHOW PROCESSLIST;
16Id	User	Host	db	Command	Time	State	Info	Progress
17<Id>	root	<Host>	test	Query	<Time>	<State>	SHOW PROCESSLIST	0.000
18SET SESSION transaction_prealloc_size=1024*1024*1024*5;
19SHOW PROCESSLIST;
20Id	User	Host	db	Command	Time	State	Info	Progress
21<Id>	root	<Host>	test	Query	<Time>	<State>	SHOW PROCESSLIST	0.000
22