when are new tablename-UUID directories created? (in relation to incremental backups)

[Johann Tagle]

Hello.  Wondering when are new tablename-UUID directories are created?  One book (Cassandra: the Definitive Guide) mentioned it is related to change in table schema.  What kind of changes can actually trigger this?  I tried adding another field to a table and doing a flush but no new directory is created.

I'm asking this in relation to doing incremental backups - right now I'm working on a script that only checks table directories that contains the name of the last snapshot (e.g. if tablename-UUID/snapshots/SNAPSHOT_NAME is present, then check tablename-UUID/backups/ for incremental backup files).  I need to know if I need to watch out for newer tablename-UUID directories that contain incremental backups that are also applicable to the last snapshot.

Thanks

Johann

[Tomasz Grabiec]

On Tue, Aug 15, 2017 at 11:19 AM, Johann Tagle <johan...@gmail.com> wrote:

Hello.  Wondering when are new tablename-UUID directories are created?  One book (Cassandra: the Definitive Guide) mentioned it is related to change in table schema.  What kind of changes can actually trigger this?  I tried adding another field to a table and doing a flush but no new directory is created.

A table has a single UUID (and a single tablename-UUID directory) throughout its life time. The UUID is assigned on coordinator node when table creating statement is executed. The directories are created on replicas as they process schema change notifications.

You can get different tablename-UUID directories after you dropped a table and recreated with the same name. Only one table with given name is active at a time.

You can also end up with two directories if you try to create a table with given name concurrently on two different nodes. You shouldn't try to do that though (https://github.com/scylladb/scylla/issues/420).

 

I'm asking this in relation to doing incremental backups - right now I'm working on a script that only checks table directories that contains the name of the last snapshot (e.g. if tablename-UUID/snapshots/SNAPSHOT_NAME is present, then check tablename-UUID/backups/ for incremental backup files).  I need to know if I need to watch out for newer tablename-UUID directories that contain incremental backups that are also applicable to the last snapshot.

Thanks

Johann

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[Johann Tagle]

Thanks Tomasz!  

On Wednesday, August 16, 2017 at 6:09:15 PM UTC+8, Tomasz Grabiec wrote:

On Tue, Aug 15, 2017 at 11:19 AM, Johann Tagle <johan...@gmail.com> wrote:

Hello.  Wondering when are new tablename-UUID directories are created?  One book (Cassandra: the Definitive Guide) mentioned it is related to change in table schema.  What kind of changes can actually trigger this?  I tried adding another field to a table and doing a flush but no new directory is created.

A table has a single UUID (and a single tablename-UUID directory) throughout its life time. The UUID is assigned on coordinator node when table creating statement is executed. The directories are created on replicas as they process schema change notifications.

You can get different tablename-UUID directories after you dropped a table and recreated with the same name. Only one table with given name is active at a time.

You can also end up with two directories if you try to create a table with given name concurrently on two different nodes. You shouldn't try to do that though (https://github.com/scylladb/scylla/issues/420).

 

I'm asking this in relation to doing incremental backups - right now I'm working on a script that only checks table directories that contains the name of the last snapshot (e.g. if tablename-UUID/snapshots/SNAPSHOT_NAME is present, then check tablename-UUID/backups/ for incremental backup files).  I need to know if I need to watch out for newer tablename-UUID directories that contain incremental backups that are also applicable to the last snapshot.

Thanks

Johann

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