How (if at all) should I alter my table and change the compaction strategy to DTCS?

I have cassandra table defined as:

CREATE TABLE db.table (
    value text,
    time timestamp,
    sid text,
    PRIMARY KEY (sid, time)
) WITH CLUSTERING ORDER BY (time ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
    AND comment = ''
    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy'}
    AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99.0PERCENTILE';

Table is pretty big, here are data files:

```
root@server:/home# ls -l /var/lib/cassandra/data/db/table/*-Data.db -h
-rw-r--r-- 1 cassandra cassandra 8.7G Aug 16 00:14 /var/lib/cassandra/data/db/table/db-table-ka-200785-Data.db
-rw-r--r-- 1 cassandra cassandra 2.2G Nov 5 21:28 /var/lib/cassandra/data/db/table/db-table-ka-208079-Data.db
-rw-r--r-- 1 cassandra cassandra 20G Nov 20 20:55 /var/lib/cassandra/data/db/table/db-table-ka-208702-Data.db
-rw-r--r-- 1 cassandra cassandra 18G Dec 17 17:31 /var/lib/cassandra/data/db/table/db-table-ka-210089-Data.db
-rw-r--r-- 1 cassandra cassandra 455M Dec 18 14:15 /var/lib/cassandra/data/db/table/db-table-ka-210153-Data.db
-rw-r--r-- 1 cassandra cassandra 4.4G Dec 27 09:27 /var/lib/cassandra/data/db/table/db-table-ka-210477-Data.db
-rw-r--r-- 1 cassandra cassandra 3.9G Jan 7 14:50 /var/lib/cassandra/data/db/table/db-table-ka-210834-Data.db
-rw-r--r-- 1 cassandra cassandra 4.1G Jan 16 04:47 /var/lib/cassandra/data/db/table/db-table-ka-211203-Data.db
-rw-r--r-- 1 cassandra cassandra 997M Jan 19 08:56 /var/lib/cassandra/data/db/table/db-table-ka-211292-Data.db
-rw-r--r-- 1 cassandra cassandra 1.1G Jan 20 23:24 /var/lib/cassandra/data/db/table/db-

You can't, because that would require rewriting all your data on disk in a different order, while resorting at runtime until the rewrite was done, which would result in an unacceptable hit to performance. You'll need to create a new table and bulk-load it in.

StackExchange Database Administrators Q#161881, answer score: 3