Concurrency issue on querying the SQL catalog

[monetdb-team]

Date: 2015-04-22 21:19:33 +0200
From: @mlkersten
To: SQL devs <>
Version: 11.17.13 (Jan2014-SP1)
CC: @njnes

Last updated: 2015-06-22 22:32:21 +0200

Comment 20829

Date: 2015-04-22 21:19:33 +0200
From: @mlkersten

User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:37.0) Gecko/20100101 Firefox/37.0
Build Identifier:

In one window the 254 files of airtraffic are loaded one by one into a merge table.
In another window progress is monitored using a query. Then it can happen
that the mclient simply quits without output.
....
working session
....
sql>select * from tables where name ilike '%ontime%';
+-------+---------------+-----------+-------+------+--------+---------------+--------+-----------+
| id | name | schema_id | query | type | system | commit_action | access | temporary |
+=======+===============+===========+=======+======+========+===============+========+===========+
| 7365 | ontime | 2000 | null | 3 | false | 0 | 0 | 0 |
| 7460 | ontime1988_1 | 2000 | null | 0 | false | 0 | 1 | 0 |
.....
| 10880 | ontime1991_1 | 2000 | null | 0 | false | 0 | 1 | 0 |
| 10975 | ontime1991_2 | 2000 | null | 0 | false | 0 | 0 | 0 |
+-------+---------------+-----------+-------+------+--------+---------------+--------+-----------+
39 tuples (5.8s)
sql>^C

stopped and restart session

mk@vienna::/export/scratch1/mk/default/package/sql/test/mergetables/Tests> mclient -d airtraffic
Welcome to mclient, the MonetDB/SQL interactive terminal (unreleased)
Database: MonetDB v11.20.0 (unreleased), 'mapi:monetdb://vienna.ins.cwi.nl:50000/airtraffic'
Type \q to quit, ? for a list of available commands
auto commit mode: on
sql>select * from tables where name ilike '%ontime%';
sql>
mk@vienna::/export/scratch1/mk/default/package/sql/test/mergetables/Tests>

It can even happen that establishing a new connection fails as well.

Reproducible: Sometimes

Comment 20830

Date: 2015-04-22 21:21:50 +0200
From: @mlkersten

Putting the debugger on the server and attempting a new session gives the following trace.

0 0x000000378a035877 in raise () from /lib64/libc.so.6
1 0x000000378a036f68 in abort () from /lib64/libc.so.6
2 0x000000378a02e7d6 in __assert_fail_base () from /lib64/libc.so.6
3 0x000000378a02e882 in __assert_fail () from /lib64/libc.so.6
4 0x00007f7c5acd191c in schema_table_find (s=0x7f7c301106b0, ot=0x7f7c444916a0) at /export/scratch1/mk/default//package/sql/storage/store.c:2082
5 0x00007f7c5acd19c3 in table_find (tr=0x7f7c300016a0, flag=0, ot=0x7f7c444916a0, omt=0x7f7c30120460) at /export/scratch1/mk/default//package/sql/storage/store.c:2099
6 0x00007f7c5acd5062 in reset_changeset (tr=0x7f7c300016a0, fs=0x7f7c30120548, pfs=0x2b0b328, b=0x7f7c30120460, rf=0x0, fd=0x7f7c5acd1928 <table_find>) at /export/scratch1/mk/default//package/sql/storage/store.c:3056
7 0x00007f7c5acd55d1 in reset_table (tr=0x7f7c300016a0, ft=0x7f7c30120460, pft=0x2b0b240) at /export/scratch1/mk/default//package/sql/storage/store.c:3150
8 0x00007f7c5acd4e51 in reset_changeset (tr=0x7f7c300016a0, fs=0x7f7c301106e0, pfs=0x2aa1be0, b=0x7f7c301106b0, rf=0x7f7c5acd5494 <reset_table>, fd=0x7f7c5acd19de <table_dup>)
at /export/scratch1/mk/default//package/sql/storage/store.c:3028
9 0x00007f7c5acd5a96 in reset_schema (tr=0x7f7c300016a0, fs=0x7f7c301106b0, pfs=0x2aa1bb0) at /export/scratch1/mk/default//package/sql/storage/store.c:3224
10 0x00007f7c5acd4e51 in reset_changeset (tr=0x7f7c300016a0, fs=0x7f7c300016d0, pfs=0x298f910, b=0x298f8e0, rf=0x7f7c5acd57c7 <reset_schema>, fd=0x7f7c5acd24c4 <schema_dup>)
at /export/scratch1/mk/default//package/sql/storage/store.c:3028
11 0x00007f7c5acd5ba0 in reset_trans (tr=0x7f7c300016a0, ptr=0x298f8e0) at /export/scratch1/mk/default//package/sql/storage/store.c:3241
12 0x00007f7c5acddee7 in sql_trans_begin (s=0x7f7c48002f70) at /export/scratch1/mk/default//package/sql/storage/store.c:5142
13 0x00007f7c5ac41343 in mvc_trans (m=0x7f7c4810e980) at /export/scratch1/mk/default//package/sql/server/sql_mvc.c:169
14 0x00007f7c5ab885b1 in monet5_user_get_def_schema (m=0x7f7c4810e980, user=0) at /export/scratch1/mk/default//package/sql/backends/monet5/sql_user.c:424

Comment 20838

Date: 2015-04-24 09:42:25 +0200
From: @mlkersten

Fixed.

Comment 20839

Date: 2015-04-24 11:04:05 +0200
From: @njnes

fixed by a split of the reset_table code (ie first al tables then the table parts of a merge table).