Empty result sets may return for a query even when the qualified
data is not empty, or a hang may occur, if both the conditions
below are met:
1. The query is against a column-organized table
2. There are enough tables in the table's tablespace so that the
table's table_id is negative in SYSCAT.TABLES.
The problem will typically only manifest when there are > 12000
column-organized tables in a single tablespace. If there are a
mix of row-organized and column-organized tables in the same
tablespace, then the overall number of tables required to
trigger the problem will be higher (since the row-organized
tables do not involve the creation of the 'extra' synopsis
table, while for each column-organized table, there will
typically be a synopsis table created). Buf if there are
partition tables, the overall number of tables required to
trigger the problem will be lower because DB2 will create a
'extra' table for each partition.
This problem doesn't happen on AIX due to its characteristic.
An example:
db2 "create table test(a int,b varchar(10)) organize by column"
DB20000I The SQL command completed successfully.
db2 "insert into test values(1,'aa')"
DB20000I The SQL command completed successfully.
db2 "select * from test"
A B
----------- ----------
0 record(s) selected.
db2 "select substr(TABNAME,1,20) TABNAME, TABLEID,TBSPACEID
from SYSCAT.TABLES where TABNAME='TEST' "
TABNAME TABLEID TBSPACEID
-------------------- ------- ---------
TEST -27349 3
1 record(s) selected.
Example of the hang stack must have sqloWaitEDUWaitPost and
sqlrr_smp_router:
semtimedop
sqloWaitEDUWaitPost
sqlriCdeOpen
sqlriCdeQuery
sqlriSectInvoke
sqlrr_smp_router
sqlrr_subagent_router |
