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From Shawn Heisey <>
Subject Re: Database logins and active sessions
Date Thu, 08 Feb 2018 07:57:59 GMT
On 2/7/2018 11:40 PM, Srinivas Kashyap wrote:
> We have configured Solr index server on tomcat and fetch the data from database to index
the data. We have implemented delta query indexing based on modify_ts.

What version of Solr?  Just as an FYI:  Since version 5.0, running in 
user-provided containers (like Tomcat) is not a supported configuration.

> In our data-config.xml we have a parent entity and 17 child entity. We have 18 such solr
cores. When we call delta-import on a core, it executes 18 SQL query to query database.
> Each time delta-import is opening a new session onto database. Log-in and log-out though
happening at a split second, we are finding millions of login and logout at database.
> As per our DBA, login and logout are costly operation in terms of server resources.
> Is there a way to reduce the number of  logins and logouts and have a persistent DB connection
from solr?

Directly, with a JDBC driver configured in the dataimport handler? 
Probably not.  But it looks like there may be a workaround -- setting up 
a JNDI datasource in your servlet container, and letting that handle the 
connection pooling for you.

It is likely that your container can set up connection pooling with most 
JDBC drivers, not just MySQL.

The dataimport handler is a useful module, but it has limitations.  If 
you write your own indexing program that is fully aware of your source 
data, you're likely to get better results.

Something else to consider -- sometimes by clever use of SQL JOINs, you 
can put the information gathering done by child entities into the main 
query of the parent entity.  If you can do that and eliminate all your 
child entities, then Solr will make exactly ONE query to your database 
for any import operation, and you won't need to worry about reusing open 


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