使用GDB调试gp(转载)

使用 gdb 调试 postgres greenplum

zalax3030人评论715人阅读2012-07-11 10:07:15

 

错误信息的获取途径有几种 : 

1. 最简单的就是看PostgreSQL的log文件.

2. 在PostgreSQL中可以使用psql的 \set VERBOSITY verbose 来输出详细的错误信息, 

3. 或者使用linux的strace跟踪这个发生错误的进程.

4. 使用gdb (GNU Debugger) 来调试则是一种比较深入但是非常有用的工具.

下面就以前面我在使用pgsql_fdw时遇到的问题使用gdb来做个简单的演示 : 

要让postgresql能够使用gdb进行调试, 首先要在编译PostgreSQL时打开enable-debug.

例如, 使用如下方法编译 : 

 ./configure --prefix=/home/digoal/pgsql91 --with-pgport=1999 --with-perl --with-python --with-openssl --with-pam --without-ldap --with-libxml --with-libxslt --enable-thread-safety --with-wal-blocksize=16 --enable-debug && gmake worldsudo gmake install-world 

 

 

在满足这个条件后, 初始化数据库

initdb -D $PGDATA -E UTF8 --locale=C -W -U postgres

 

使用gdb进行调试 : 

会话1 : 

获取当前进程的pid.

 digoal@db-172-16-3-33-> psql postgres postgrespsql (9.1.3)Type "help" for help.postgres=# select pg_backend_pid(); pg_backend_pid ----------------          26841(1 row)postgres=# \set VERBOSITY verbose 

 

 

会话2 : 

使用gdb, 绑定到会话1获取到的进程PID.

 digoal@db-172-16-3-33-> gdb(gdb) attach 26841 

 

在出错的函数处设置断点(b getTypeOutputInfo) : 

 (gdb) b getTypeOutputInfoBreakpoint 1 at 0x6cbaf0: file lsyscache.c, line 2434. 

 

 

会话1 : 

执行那个报错的函数 : 

postgres=# select f_test();

 

 

会话2 : 

继续执行(c), 跟踪到getTypeOutputInfo的输入参数如下 : 

 (gdb) cContinuing.Breakpoint 1, getTypeOutputInfo (type=0, typOutput=0x7fff1c55df58, typIsVarlena=0x7fff1c55df5f "") at lsyscache.c:24342434    { 

 

查看截止到断点前的所有调用(bt或backtrace) : 

注意这里的结果和实际的调用顺序是反的, 如, #1的execute_query调用了#0的getTypeOutputInfo

 (gdb) bt#0  getTypeOutputInfo (type=0, typOutput=0x7fff1c55df58, typIsVarlena=0x7fff1c55df5f "") at lsyscache.c:2434#1  0x00002b066328943b in execute_query (node=0x17f14c70) at pgsql_fdw.c:668#2  0x00002b066328a00f in pgsqlIterateForeignScan (node=0x0) at pgsql_fdw.c:352#3  0x0000000000573a6f in ForeignNext (node=0x0) at nodeForeignscan.c:49#4  0x0000000000560b1e in ExecScanFetch (node=0x17f14c70, accessMtd=0x573a30 <ForeignNext>, recheckMtd=0x5738b0 <ForeignRecheck>)    at execScan.c:82#5  ExecScan (node=0x17f14c70, accessMtd=0x573a30 <ForeignNext>, recheckMtd=0x5738b0 <ForeignRecheck>) at execScan.c:167#6  0x0000000000559dda in ExecProcNode (node=0x17f14c70) at execProcnode.c:432#7  0x000000000056b5c8 in ExecLimit (node=0x17f14970) at nodeLimit.c:91#8  0x0000000000559eaa in ExecProcNode (node=0x17f14970) at execProcnode.c:490#9  0x0000000000558d21 in ExecutePlan (queryDesc=0x17f12850, direction=475389784, count=0) at execMain.c:1439#10 standard_ExecutorRun (queryDesc=0x17f12850, direction=475389784, count=0) at execMain.c:313#11 0x00000000005788a3 in _SPI_execute_plan (plan=0x17f16870, paramLI=0x17e0ae68, snapshot=<value optimized out>,     crosscheck_snapshot=0x0, read_only=0 '\000', fire_triggers=1 '\001', tcount=0) at spi.c:2110#12 0x0000000000578c9d in SPI_execute_plan_with_paramlist (plan=0x17f16870, params=0x17e0ae68, read_only=0 '\000', tcount=0)    at spi.c:423#13 0x00002b0663072133 in exec_run_select (estate=0x7fff1c55e580, expr=0x17f0c880, maxtuples=0, portalP=0x0) at pl_exec.c:4580#14 0x00002b0663075809 in exec_stmt (estate=0x7fff1c55e580, stmts=<value optimized out>) at pl_exec.c:1413#15 exec_stmts (estate=0x7fff1c55e580, stmts=<value optimized out>) at pl_exec.c:1248#16 0x00002b0663075628 in exec_stmt_block (estate=0x7fff1c55e580, block=0x17f0cb40) at pl_exec.c:1186#17 0x00002b0663078273 in plpgsql_exec_function (func=0x17eee148, fcinfo=0x17f18940) at pl_exec.c:324#18 0x00002b066306d3e3 in plpgsql_call_handler (fcinfo=0x17f18940) at pl_handler.c:122#19 0x000000000055d5be in ExecMakeFunctionResult (fcache=0x17f188d0, econtext=0x17f186e0, isNull=0x17f19258 "\024",     isDone=0x17f19370) at execQual.c:1824#20 0x000000000055a35a in ExecTargetList (projInfo=<value optimized out>, isDone=0x7fff1c55e92c) at execQual.c:5104#21 ExecProject (projInfo=<value optimized out>, isDone=0x7fff1c55e92c) at execQual.c:5319#22 0x000000000056fcd3 in ExecResult (node=0x17f185d0) at nodeResult.c:155#23 0x0000000000559d06 in ExecProcNode (node=0x17f185d0) at execProcnode.c:367#24 0x0000000000558d21 in ExecutePlan (queryDesc=0x17ebbfa0, direction=475389784, count=0) at execMain.c:1439#25 standard_ExecutorRun (queryDesc=0x17ebbfa0, direction=475389784, count=0) at execMain.c:313#26 0x000000000061d9d4 in PortalRunSelect (portal=0x17eb9f90, forward=<value optimized out>, count=0, dest=0x17eb0050)    at pquery.c:943#27 0x000000000061eee0 in PortalRun (portal=0x17eb9f90, count=9223372036854775807, isTopLevel=1 '\001', dest=0x17eb0050,     altdest=0x17eb0050, completionTag=0x7fff1c55eb90 "") at pquery.c:787#28 0x000000000061bbbb in exec_simple_query (query_string=0x17eae9c0 "select f_test();") at postgres.c:1018#29 0x000000000061c3c4 in PostgresMain (argc=<value optimized out>, argv=<value optimized out>, username=<value optimized out>)    at postgres.c:3926#30 0x00000000005e191b in ServerLoop () at postmaster.c:3606#31 0x00000000005e253c in PostmasterMain (argc=1, argv=0x17e05090) at postmaster.c:1116---Type <return> to continue, or q <return> to quit--- #32 0x0000000000586d6e in main (argc=1, argv=<value optimized out>) at main.c:199 

 

其他常用gdb指令 : 

print

next

nexti

【参考】

1. (gdb) 是gdb的命令行提示符.

2. http://en.wikipedia.org/wiki/GNU_Debugger 

3. http://wiki.postgresql.org/wiki/Pgsrcstructure

4. gdb 所有指令 : 

(gdb) help all