MySQL源码学习系列（一）-- 环境准备及常用命令

/usr/local/mysql-8.0.40/runtime_output_directory/mysqld --defaults-group-suffix=.1 --defaults-file=/usr/local/mysql-8.0.40/mysql-test/var/my.cnf --user=root --log-output=file --explain-format=TRADITIONAL_STRICT --loose-debug-sync-timeout=600 --core-file


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root@Ubuntu22045:~# usr/local/mysql-8.0.40/runtime_output_directory/mysql -uroot -P 13000 -h 127.0.0.1
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root@Ubuntu22045:~# ps -ef|grep mysqld
root        3656    2986  0 3月25 pts/0   00:01:56 usr/local/mysql-8.0.40/runtime_output_directory/mysqld --defaults-group-suffix=.1 --defaults-file=/usr/local/mysql-8.0.40/mysql-test/var/my.cnf --user=root --log-output=file --explain-format=TRADITIONAL_STRICT --loose-debug-sync-timeout=600 --core-file
root       29180   29138  0 17:11 pts/4    00:00:00 grep --color=auto mysqld
root@Ubuntu22045:~# gdb -p 3656
GNU gdb (Ubuntu 12.1-0ubuntu1~22.04.2) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.


For help, type "help".
Type "apropos word" to search for commands related to "word".
Attaching to process 3656
[New LWP 3669]
[New LWP 3670]
[New LWP 3671]


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(gdb) b mysql_execute_command
Breakpoint 1 at 0x5c2990212d77: file usr/local/mysql-8.0.40/sql/sql_parse.cc, line 2946.
(gdb) c
Continuing.
[Switching to Thread 0x74e7619ff640 (LWP 3867)]


Thread 38 "connection" hit Breakpoint 1, mysql_execute_command (thd=0x74e6c4003fd0, first_level=true) at usr/local/mysql-8.0.40/sql/sql_parse.cc:2946
2946	int mysql_execute_command(THD *thd, bool first_level) {
(gdb) p thd.m_query_string
$1 = {str = 0x74e6c40139d0 "select now()", length = 12}
(gdb)
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(gdb) b dispatch_command 
Breakpoint 2 at 0x5c59b7e7c8fd: file usr/local/mysql-8.0.40/sql/sql_parse.cc, line 1689.
(gdb) c
Continuing.
[Thread 0x7ba3a9000640 (LWP 29321) exited]
[Switching to Thread 0x7ba3a55ff640 (LWP 29337)]


Thread 39 "connection" hit Breakpoint 2, dispatch_command (thd=0x7ba3080012e0, com_data=0x7ba3a55fe300, command=COM_QUERY) at usr/local/mysql-8.0.40/sql/sql_parse.cc:1689
1689	                      enum enum_server_command command) {
(gdb) 


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(gdb) b Query_expression::execute
Breakpoint 3 at 0x5c59b7fd59fd: file /usr/local/mysql-8.0.40/sql/sql_union.cc, line 1809.
(gdb) c
Continuing.


Thread 39 "connection" hit Breakpoint 1, mysql_execute_command (thd=0x7ba3080012e0, first_level=true) at /usr/local/mysql-8.0.40/sql/sql_parse.cc:2946
2946	int mysql_execute_command(THD *thd, bool first_level) {
(gdb) c
Continuing.


Thread 39 "connection" hit Breakpoint 3, Query_expression::execute (this=0x7ba30811f2b0, thd=0x7ba3080012e0) at /usr/local/mysql-8.0.40/sql/sql_union.cc:1809
1809	bool Query_expression::execute(THD *thd) {
(gdb) l
1804	  @param thd          thread handle
1805	
1806	  @returns false if success, true if error
1807	*/
1808	
1809	bool Query_expression::execute(THD *thd) {
1810	  DBUG_TRACE;
1811	  assert(is_optimized());
1812	
1813	  if (is_executed() && !uncacheable) return false;
(gdb)
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