The same table name with two different CF IDs is not just "temporary
schema disagreements", it's much worse than that. This breaks the
eventual consistency guarantee, and leads to silent data corruption.
It's silently happening in the background, and you don't realise it
until you suddenly do, and then everything seems to blow up at the same
time. You need to sort this out ASAP.
On 05/12/2023 19:57, Sébastien Rebecchi wrote:
Hi Bowen,
Thanks for your answer.
I was thinking of extreme use cases, but as far as I am concerned I
can deal with creation and deletion of 2 tables every 6 hours for a
keyspace. So it lets around 8 folders of deleted tables per day -
sometimes more cause I can see sometimes 2 folders created for a same
table name, with 2 different ids, caused by temporary schema
disagreements I guess.
Basically it means 20 years before the KS folder has 65K subfolders,
so I would say I have time to think of redesigning the data model ^^
Nevertheless, does it sound too much in terms of thombstones in the
systems tables (with the default GC grace period of 10 days)?
Sébastien.
Le mar. 5 déc. 2023, 12:19, Bowen Song via user
<user@cassandra.apache.org> a écrit :
Please rethink your use case. Create and delete tables
concurrently often lead to schema disagreement. Even doing so on a
single node sequentially will lead to a large number of tombstones
in the system tables.
On 04/12/2023 19:55, Sébastien Rebecchi wrote:
Thank you Dipan.
Do you know if there is a good reason for Cassandra to let tables
folder even when there is no snapshot?
I'm thinking of use cases where there is the need to create and
delete small tables at a high rate. You could quickly end with
more than 65K (limit of ext4) subdirectories in the KS directory,
while 99.9.. % of them are residual of deleted tables.
That looks quite dirty from Cassandra to not clean its own
"garbage" by itself, and quite dangerous for the end user to have
to do it alone, don't you think so?
Thanks,
Sébastien.
Le lun. 4 déc. 2023, 11:28, Dipan Shah <dipan....@hotmail.com> a
écrit :
Hello Sebastien,
There are no inbuilt tools that will automatically remove
folders of deleted tables.
Thanks,
Dipan Shah
------------------------------------------------------------------------
*From:* Sébastien Rebecchi <srebec...@kameleoon.com>
*Sent:* 04 December 2023 13:54
*To:* user@cassandra.apache.org <user@cassandra.apache.org>
*Subject:* Remove folders of deleted tables
Hello,
When we delete a table with Cassandra, it lets the folder of
that table on file system, even if there is no snapshot (auto
snapshots disabled).
So we end with the empty folder {data folder}/{keyspace
name}/{table name-table id} containing only 1 subfolder,
backups, which is itself empty.
Is there a way to automatically remove folders of deleted tables?
Sébastien.
