What does this error mean?
This error means that the total size for the index summary has exceeded 2GB and no more entries will be added to the index summary.
Why does this error occur?
This error occurs when the number of sampled entries in an SSTable results in using more than the 2GB threshold for the Index Summary. The SSTable in question is too large to allow for a full sampling of entries from the SSTable. This is not an error of major concern, as Cassandra will still function as normal. The only downside is when retrieving data whose partition index is after the final index summary entry. This will result in scans of the remaining portion of an SSTable to get to the partition key if it is not already in the key cache.
How do you fix this error?
Increasing the min_index_interval will reduce the number of entries in the partition index, and will reduce the number of sample entries in the Index Summary, allowing a full sampling of the SSTable to occur. You can adjust this using CQL:
cqlsh> ALTER TABLE table_name WITH min_index_interval = 256;