I am only doing inserts to cassandra. While inserting , not nulls are only inserted to avoid tombstones. But few records are inserted with TTL. But then doing select count(*) from table gives following errors -
Read 76 live rows and 1324 tombstone cells for query SELECT * FROM xx.yy WHERE token(y) >= token(fc872571-1253-45a1-ada3-d6f5a96668e8) LIMIT 100 (see tombstone_warn_threshold)
Do TTL inserts lead to tombstones in cassandra 3.7 ? How can the warning be mitigated ?
There are no updates done only inserts , some records without TTL , others with TTL
From datastax documentation: https://docs.datastax.com/en/cql/3.1/cql/cql_using/use_expire_c.html
After the number of seconds since the column's creation exceeds the TTL value, TTL data is considered expired and is included in results. Expired data is marked with a tombstone after on the next read on the read path, but it remains for a maximum of gc_grace_seconds. After this amount of time, the tombstoned data is automatically removed during the normal compaction and repair processes.
These entries will be treated as tombstones until compaction or repair.
To add one more point for TTL and compaction. Even though, after gc_grace_seconds, the default setting for compaction only kicks off depending on tombstone_compaction_interval and tombstone_threshold
Previously, we were having read timeout issue due to high number of tombstones for tables having high number of records. Eventually, we need to reduce tombstone_threshold as well as enable unchecked_tombstone_compaction to make compaction process triggered more frequently.
You can refer to the below docs for more details
来源：https://stackoverflow.com/questions/47086869/ttl-in-cassandra-creating-tombstones