[GitHub] [cassandra] blerer commented on a change in pull request #1276: CASSANDRA-17048: UUID based sstable generation numbers

[GitBox <gi...@apache.org>]

blerer commented on a change in pull request #1276:
URL: https://github.com/apache/cassandra/pull/1276#discussion_r826822604



##########
File path: src/java/org/apache/cassandra/db/SystemKeyspace.java
##########
@@ -255,6 +251,18 @@ private SystemKeyspace()
                 + "PRIMARY KEY ((keyspace_name, columnfamily_name, generation)))")
                 .build();
 
+    private static final TableMetadata SSTableActivity =
+        parse(SSTABLE_ACTIVITY_V2,
+                "historic sstable read rates",
+                "CREATE TABLE %s ("
+                + "keyspace_name text,"
+                + "columnfamily_name text,"
+                + "generation blob,"

Review comment:
       +1

##########
File path: conf/cassandra.yaml
##########
@@ -932,6 +932,13 @@ compaction_throughput_mb_per_sec: 64
 # between the sstables, reducing page cache churn and keeping hot rows hot
 sstable_preemptive_open_interval_in_mb: 50
 
+# Starting from 4.1 sstables support UUID based generation identifiers. They are disabled by default
+# because once enabled, there is no easy way to downgrade. When the node is restarted with this option
+# set to true, each newly created sstable will have UUID based generation identifier and such files are
+# not readable by previous Cassandra versions. At some point, this option will become true by default
+# and eventually get removed from the configuration.
+enable_uuid_generation_identifiers: false

Review comment:
       It is tricky because we cannot really say to people: "use that functionality it is experimental and by the way there is no going back".




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