Archive for December, 2008

Tips: Bash Prompt and Oracle

Tuesday, December 30th, 2008 
export PS1=\u@\h:\w\$

I disagree with default bash prompt. Do you? It’s quote common to work with long paths:

ludovico@host:/u01/app/oracle/product/10.2.0/network/admin$ \
/nooo/this/command/line/is/really/long/and/offcourse -I \
-will -wrap -my -command -line

and, when working on multi-database environments I need to check my environment:

env | grep -i oracle
#or
echo $ORACLE_SID
echo $ORACLE_HOME

I currently use this prompt, instead:

export PS1=$'\\n# [ $LOGNAME@\h:$PWD [\\t] [`ohvers` SID:${ORACLE_SID:-"no sid"}] ]\\n# '
 
# [ ludovico@caldara_2k:/u01/app/oracle/product/10.2.0/db_1/network/admin [23:15:58] [10.2.0 SID:orcl] ]
#

What is `ohvers`?? I defined this function to get the version of oracle from my ORACLE_HOME variable:

ohvers ()
{
echo -n $ORACLE_HOME | sed -n 's/.*\/\([[:digit:].]\+\)\/.*/\1/p'
}

Pros:

  • I have a blank line that separate my prompt from previous output
  • I get the system clock (useful when saving my konsole history. Did I say konsole?)
  • I can see my Oracle Environment before launching dangerous commands
  • I have an empty line to start my endless commands
  • I have a lot of sharps “#” : they are fine against wrong copy&paste operations…

Suggestions?

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Posted in Linux, Oracle Database | 1 Comment »

JBoss Portal and MySQL scalability: What The…???

Wednesday, December 10th, 2008

I found several queries running on a MySQL 5.0 database like this one:

SELECT PATH, NAME FROM JBP_OBJECT_NODE  WHERE PK IN (
SELECT NODE_KEY FROM JBP_OBJECT_NODE_SEC WHERE ROLE IN (
SELECT jr.jbp_name FROM jbp_users ju, jbp_role_membership jrm,
jbp_roles jr
WHERE jrm.jbp_uid = ju.jbp_uid
AND jr.jbp_rid = jrm.jbp_rid
AND ju.jbp_uname = 'LUDOVICO'
AND ju.jbp_enabled = 1));

This query is related to JBoss Portal and does a full scan on table JBP_OBJECT_NODE.

It has bad performances (>0.8 sec) with just a few records:

mysql> select count(*) from JBP_OBJECT_NODE;
+———-+
| count(*) |
+———-+
|    33461 |
+———-+

If I rewrite the query using an inner join (à la Oracle, please forgive me) instead of a subquery I get an index scan:

SELECT DISTINCT a.PATH, a.NAME /* , b.NODE_KEY */ FROM  JBP_OBJECT_NODE
a, JBP_OBJECT_NODE_SEC b
WHERE a.pk=b.NODE_KEY
AND b.ROLE IN (
SELECT jr.jbp_name FROM jbp_users ju, jbp_role_membership jrm,
jbp_roles jr
WHERE jrm.jbp_uid = ju.jbp_uid
AND jr.jbp_rid = jrm.jbp_rid
AND ju.jbp_uname = 'UTDEMO'
AND ju.jbp_enabled = 1);

With 30k records the execution time falls down from 0.8 secs to 0.01 secs…
That’s NOT all! I found this open bug:

https://jira.jboss.org/jira/browse/JBPORTAL-2040

With many users registered in, the JBoss Portal Admin console tooks over a minute to show a single page…

I don’t like portals…

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Posted in JBoss, MySQL, Performance | 2 Comments »