FrankChen021 opened a new issue #9899: URL: https://github.com/apache/druid/issues/9899
this issue is related to #9755 . At first I thought it was because there were too many rows in the `druid_segments` table. So we killed unused segments through API to reduce the records in that table. After that, the count of rows dropped from about 360,000 to about 50,000. But our DBA still reported that there were slow queries there, which pointed to statement `SELECT payload FROM druid_segments WHERE used=true`. So I ran this SQL from local mysql client, and it reported that it took more than 90 seconds to get the result. I ran another SQL `SELECT id FROM druid_segments WHERE used=true` from local, which reported that it took more than 12 seconds to complete. Since the `payload` field in database is a `LONGBLOB`, I guess the reason why the query is so slow is because the return set is too large in bytes, which takes a long time to transmit data from MySQL server to client in network. ### Affected Version the version we currently use is 0.16.0. since this issue is related to database, Ii think the latest version is still affected ### Description  ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
