Understand Query Performance

Querying an erasure coded data might have an impact on the performance. If you notice performance degradation, you can troubleshoot it by running the PROFILE command. You can also use CM to quickly identify the cause.

[localhost:21000] functional> select * from functional.alltypes;
[localhost:21000] functional> profile;

The PROFILE statement gives you an outline of the logical steps that a query will perform. It will include erasure coding related information in the profile as BytesReadErasureCoded. In the PROFILE output, look for the excerpts ExecSummary and Query Timeline, and then drill down into the particular fragment details to understand the query performance.