slow performance DB Reader



I am experiencing a slow DB Reader node. The SQL query when executed with SQL developer takes less than a second, but the same query in KNIME takes > 15 minutes. Something is wrong. Can someone help me? I tried changing the fetchsize from 1000 to 100000, but that doesn’t change the result. I have also read on forum that the .metadata folder’s content might be the issue.

Thanks, Frederik



Hi there @fstouten,

welcome to KNIME Community!

Can you share more information like what KNIME version are you using? What database are you talking about? What driver did you register?




The difference most likely is that in SQL developer only the first 50-200 rows are fetched (how many depends on your settings but I think 50 is default). If you scroll down in the resulst, more rows are fetched and the timer goes up.

In knime that query will fetch all data and depending on the number of rows and their content, it can take a while (especially LOB columns).

As a test you can limit your query to say 10’000 rows or such and then in SQL developer run it as a script instead of a query and then it will also fetch all rows. Then compare to run time of same query in KNIME. it will most likely be similar.



Thanks, that explains it of course.