bug: json format and auto_explain

Hi,

While testing the EXPLAIN BUFFERS patch I found a bug. I'm too tired to
provide a fix right now but if someone can take it I will appreciate. It seems
ExplainJSONLineEnding() doesn't expect es->grouping_stack list as a null pointer.

euler(at)harman $ ./install/bin/psql
psql (8.5devel)
Type "help" for help.

euler=# load 'auto_explain';
LOAD
euler=# set auto_explain.log_min_duration to 0;
SET
euler=# set auto_explain.log_format to 'json';
SET
euler=# explain (format json) select * from pgbench_branches inner join
pgbench_history using (bid) where bid > 100;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.
euler=# \q
euler(at)harman /a/pgsql/dev $ gdb ./install/bin/postgres ./data/core
GNU gdb 6.8
Copyright (C) 2008 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 "i686-pc-linux-gnu"...

warning: Can't read pathname for load map: Input/output error.
Reading symbols from /usr/lib/libxml2.so.2...done.
Loaded symbols for /usr/lib/libxml2.so.2
Reading symbols from /usr/lib/libssl.so.0.9.8...done.
Loaded symbols for /usr/lib/libssl.so.0.9.8
Reading symbols from /usr/lib/libcrypto.so.0.9.8...done.
Loaded symbols for /usr/lib/libcrypto.so.0.9.8
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /lib/libm.so.6...done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /usr/lib/libldap-2.4.so.2...done.
Loaded symbols for /usr/lib/libldap-2.4.so.2
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/libz.so.1...done.
Loaded symbols for /lib/libz.so.1
Reading symbols from /usr/lib/libgssapi_krb5.so.2...done.
Loaded symbols for /usr/lib/libgssapi_krb5.so.2
Reading symbols from /usr/lib/libkrb5.so.3...done.
Loaded symbols for /usr/lib/libkrb5.so.3
Reading symbols from /lib/libcom_err.so.2...done.
Loaded symbols for /lib/libcom_err.so.2
Reading symbols from /usr/lib/libk5crypto.so.3...done.
Loaded symbols for /usr/lib/libk5crypto.so.3
Reading symbols from /lib/libresolv.so.2...done.
Loaded symbols for /lib/libresolv.so.2
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /usr/lib/liblber-2.4.so.2...done.
Loaded symbols for /usr/lib/liblber-2.4.so.2
Reading symbols from /usr/lib/libsasl2.so.2...done.
Loaded symbols for /usr/lib/libsasl2.so.2
Reading symbols from /usr/lib/libgnutls.so.26...done.
Loaded symbols for /usr/lib/libgnutls.so.26
Reading symbols from /usr/lib/libkrb5support.so.0...done.
Loaded symbols for /usr/lib/libkrb5support.so.0
Reading symbols from /lib/libpthread.so.0...done.
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/libcrypt.so.1...done.
Loaded symbols for /lib/libcrypt.so.1
Reading symbols from /usr/lib/libtasn1.so.3...done.
Loaded symbols for /usr/lib/libtasn1.so.3
Reading symbols from /usr/lib/libgcrypt.so.11...done.
Loaded symbols for /usr/lib/libgcrypt.so.11
Reading symbols from /usr/lib/libgpg-error.so.0...done.
Loaded symbols for /usr/lib/libgpg-error.so.0
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
Reading symbols from /a/pgsql/dev/install/lib/auto_explain.so...done.
Loaded symbols for /a/pgsql/dev/install/lib/auto_explain.so
Core was generated by `postgres: euler euler [local] EXPLAIN '.
Program terminated with signal 11, Segmentation fault.
[New process 2751]
#0 0x081a2158 in ExplainJSONLineEnding (es=0xbfd117dc) at
/a/pgsql/dev/postgresql/src/backend/commands/explain.c:1885

warning: Source file is more recent than executable.
1885 if (linitial_int(es->grouping_stack) != 0)
(gdb) print es->grouping_stack
$1 = (List *) 0x0
(gdb) print es->str->data
$2 = 0x865b09c ""
(gdb) bt
#0 0x081a2158 in ExplainJSONLineEnding (es=0xbfd117dc) at
/a/pgsql/dev/postgresql/src/backend/commands/explain.c:1885
#1 0x081a1ada in ExplainOpenGroup (objtype=0x84fcb64 "Plan",
labelname=0x84fcb64 "Plan", labeled=1 '\001', es=0xbfd117dc) at
/a/pgsql/dev/postgresql/src/backend/commands/explain.c:1684
#2 0x0819faac in ExplainNode (plan=0x8652c98, planstate=0x8654868,
outer_plan=0x0, relationship=0x0, plan_name=0x0, es=0xbfd117dc) at
/a/pgsql/dev/postgresql/src/backend/commands/explain.c:739
#3 0x0819f393 in ExplainPrintPlan (es=0xbfd117dc, queryDesc=0x8653724) at
/a/pgsql/dev/postgresql/src/backend/commands/explain.c:474
#4 0xb7ef0010 in explain_ExecutorEnd (queryDesc=0x8653724) at
/a/pgsql/dev/postgresql/contrib/auto_explain/auto_explain.c:238
#5 0x081f1094 in ExecutorEnd (queryDesc=0x8653724) at
/a/pgsql/dev/postgresql/src/backend/executor/execMain.c:314
#6 0x0819f23d in ExplainOnePlan (plannedstmt=0x86536d8, es=0xbfd11958,
queryString=0x862ad0c "explain (format json) select * from pgbench_branches
inner join pgbench_history using (bid) where bid > 100;",
params=0x0) at /a/pgsql/dev/postgresql/src/backend/commands/explain.c:433
#7 0x0819eee6 in ExplainOneQuery (query=0x85d3620, es=0xbfd11958,
queryString=0x862ad0c "explain (format json) select * from pgbench_branches
inner join pgbench_history using (bid) where bid > 100;",
params=0x0) at /a/pgsql/dev/postgresql/src/backend/commands/explain.c:285
#8 0x0819ebd1 in ExplainQuery (stmt=0x862baf0, queryString=0x862ad0c "explain
(format json) select * from pgbench_branches inner join pgbench_history using
(bid) where bid > 100;", params=0x0,
dest=0x85d29a4) at /a/pgsql/dev/postgresql/src/backend/commands/explain.c:192
#9 0x082e89ce in ProcessUtility (parsetree=0x862baf0, queryString=0x862ad0c
"explain (format json) select * from pgbench_branches inner join
pgbench_history using (bid) where bid > 100;", params=0x0,
isTopLevel=1 '\001', dest=0x85d29a4, completionTag=0xbfd11b70 "") at
/a/pgsql/dev/postgresql/src/backend/tcop/utility.c:922
#10 0x082e6a7f in PortalRunUtility (portal=0x85d0874, utilityStmt=0x862baf0,
isTopLevel=1 '\001', dest=0x85d29a4, completionTag=0xbfd11b70 "") at
/a/pgsql/dev/postgresql/src/backend/tcop/pquery.c:1192
#11 0x082e681a in FillPortalStore (portal=0x85d0874, isTopLevel=1 '\001') at
/a/pgsql/dev/postgresql/src/backend/tcop/pquery.c:1066
#12 0x082e626e in PortalRun (portal=0x85d0874, count=2147483647, isTopLevel=1
'\001', dest=0x862bcb4, altdest=0x862bcb4, completionTag=0xbfd11cd6 "") at
/a/pgsql/dev/postgresql/src/backend/tcop/pquery.c:802
#13 0x082e0acf in exec_simple_query (query_string=0x862ad0c "explain (format
json) select * from pgbench_branches inner join pgbench_history using (bid)
where bid > 100;")
at /a/pgsql/dev/postgresql/src/backend/tcop/postgres.c:1046
#14 0x082e47d9 in PostgresMain (argc=2, argv=0x85b5358, username=0x85b5330
"euler") at /a/pgsql/dev/postgresql/src/backend/tcop/postgres.c:3624
#15 0x082a72df in BackendRun (port=0x85d4860) at
/a/pgsql/dev/postgresql/src/backend/postmaster/postmaster.c:3366
#16 0x082a69ab in BackendStartup (port=0x85d4860) at
/a/pgsql/dev/postgresql/src/backend/postmaster/postmaster.c:3073
#17 0x082a3d1c in ServerLoop () at
/a/pgsql/dev/postgresql/src/backend/postmaster/postmaster.c:1399
#18 0x082a344d in PostmasterMain (argc=3, argv=0x85b33e0) at
/a/pgsql/dev/postgresql/src/backend/postmaster/postmaster.c:1064
#19 0x0822b54b in main (argc=3, argv=0x85b33e0) at
/a/pgsql/dev/postgresql/src/backend/main/main.c:188
(gdb) quit

--
Euler Taveira de Oliveira
http://www.timbira.com/