Bugs item #2836863, was opened at 2009-08-13 13:47
Message generated for change (Comment added) made by stmane
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Category: SQL/Core
Group: SQL "stable"
Status: Open
Resolution: None
Priority: 6
Private: No
Submitted By: Stefan Manegold (stmane)
Assigned to: Niels Nes (nielsnes)
Summary: SQL: ORDER BY tests fail on 64-bit systems with 32-bit OIDs
Initial Comment:
Most probably since this checkin
===================================================================
2009/06/09 - nielsnes: sql/src/backends/monet5/sql_gencode.mx,1.319.2.4
sql/src/backends/monet5/sql_optimizer.mx,1.218.2.2
sql/src/server/rel_bin.mx,1.78.2.1
sql/src/server/sql_rel2bin.mx,1.132.2.1
sql/src/server/sql_statement.mx,1.184.2.1
ng problems with 'order' dependend statements (such as mkey xor and batcalc*
)
this solves problems with alter_table_drop_constraint as well as
SQL: test type_dump_test.SF-989257.SQL.sh fails since Feb 28
projection joins are now handled by leftjoins
===================================================================
order-by tests fail on 64-bit systems with 32-bit OIDs (the advised default
used with our 64-bit Windows installers); cf.
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/Int.64.32.d.1-Windows5.2/src_benchmarks_ATIS/select_group.out.00.html
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/GNU.64.32.d.1-Fedora10/src_test_ADT2006/slam.out.00.html
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/GNU.64.32.d.1-Fedora10/src_test_Dependencies/Dependencies.out.00.html
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/GNU.64.32.d.1-Fedora10/src_test_UserDump/create.out.00.html
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/GNU.64.32.d.1-Fedora10/src_test_bugs/subselect_multiple_unionall_where_1=1-bug-sf-1005596.out.00.html
The problem might be related to these comments in the above checkin in
sql/src/server/sql_rel2bin.mx
"
/* TODO the semijoin may break the order!! */
/* TODO semijoin may break order */
"
maybe, we need to introduce an order-preserving "left"-semijoin?
----------------------------------------------------------------------
>Comment By: Stefan Manegold (stmane)
Date: 2009-08-17 08:50
Message:
Unfortunately, the problem is even stranger:
Looking more detailed at the first failing test
http://monetdb.cwi.nl/testing/projects/monetdb/Stable/sql/.mTests103/Int.64
.32.d.1-Windows5.2/src_benchmarks_ATIS/select_group.out.00.html,
it appears that semijoin (BATsemijoin) is not even used; hence, what
seemed to be a fix (see my prev. comment) was rather by coincidence that
the test worked.
In fact, when run single-threaded (gdk_nr_threads=1), the test always
fails (only on 64-bit systems with 32-bit OIDs); however when run
multi-threaded (ghk_nr_thread>1) (on a multi-core system), the test seems
to work randomly in roughtly 50% of the attempts ...
... I'm afraid it will be a nasty task to debug and eventually fix this
one ... |-(
----------------------------------------------------------------------
Comment By: Stefan Manegold (stmane)
Date: 2009-08-16 23:27
Message:
A quick test indeed suggests that the kernel (GDK) seems to choose a
"reversed" and hence not order-preserving implementation of semijoin, and
this results in incorrect order --- at least disabling the reversed
semijoin implementation does yield the correct results.
Hence, introducing (and using) an order-preserving "left"semijoin
(basically a semijoin that is not allowed to internally use the "reversed"
implementation that loops over the right iso. the left input) should help.
Open question is, why the problems only occur on 64-bit systems with
32-bit OIDs ...
----------------------------------------------------------------------
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