Hi Ruben,
Always when I try to get some data from one especified table (it is
always the same table) top command shows postgres at 70%-80%
If you try to know witch SQLs is being executed in postgres, executing:
echo 'SELECT current_query FROM pg_stat_activity;' |
/usr/local/pgsql/bin/psql vacadb -p 5432
It shows:
- ------
SELECT def.adsrc FROM pg_catalog.pg_class c JOIN
pg_catalog.pg_attribute a ON (a.attrelid=c.oid) LEFT JOIN
pg_catalog.pg_attrdef def ON (a.attrelid=def.adrelid AND a.attnum =
def.adnum) WHERE c.oid = $1 and a.attnum = $2 AND def.adsrc LIKE
'%nextval(%'
SELECT current_query FROM pg_stat_activity;
- -------
If I am not mistaken this is a query issued by the Postgres JDBC driver
to retrieve the ResultSetMetaData. When you execute a query, Sequoia
fetches the ResultSet from the database but also the ResultSetMetaData
to get column names and other information in case you access the result
using rs.getString("column_name"). It turns out that ResultSetMetaData
fetching is very slow in Postgres. This is why we have implemented a
MetadataCache in Sequoia. The first query execution should fetch the
ResultSetMetadata but subsequent queries should get it from the cache.
If you get the controller log, you have a message that is repeating all
the time:
[...]
16:06:03,221 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:04,365 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:04,856 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:05,683 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:06,989 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:07,642 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:08,300 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:08,789 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
16:06:09,277 WARN virtualdatabase.VirtualDatabaseWorkerThread.vvacadb
Client (login:vaca,host:192.168.12.8 closed connection with server)
[...]
... and go on, until I disable backend.
This looks like this is a separate issue. A client is dropping
connections without calling Connection.close(). I cannot tell why this
is happening but at least this is the diagnosis! This usually happens
when you kill a client application or threads that had a private
connection are terminated and garbage collected.
I have no idea what's going on. Any advise would be really appreciated.
Let me know if that helps,
Emmanuel
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--
Emmanuel Cecchet
FTO @ Frog Thinker
Open Source Development & Consulting
--
Web: http://www.frogthinker.org
email: [email protected]
Skype: emmanuel_cecchet
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