Version info of my Cassandra:
[cqlsh 5.0.1 | Cassandra 2.2.5 | CQL spec 3.3.1 | Native protocol v4]
I am trying to move some huge tables (several million rows) to another keyspace. Besides "COPY to csv, and COPY from csv", is there any better solution?
Ok, I managed to get this to work on a single-node cluster running 2.2.8.
I experimented by moving my holidays
table from my presentation
keyspace over to my stackoverflow
keyspace.
Here are the steps I took:
Create the table inside the new keyspace.
This step is important, because each table has a UUID for a unique identifier, stored in the system.schema_columnfamilies
table in the cf_id
column. This id is attached to the directory names that hold the data. By copy/pasting the schema from one keyspace to another, you'll ensure that the same column names are used, but that a new unique identifier is generated.
Note: In 3.x, the identifier is stored in the system_schema.tables
table.
aploetz@cqlsh:stackoverflow> CREATE TABLE holidays (
type text,
eventtime timestamp,
beginend text,
name text,
PRIMARY KEY (type, eventtime, beginend)
) WITH CLUSTERING ORDER BY (eventtime DESC, beginend DESC);
aploetz@cqlsh:stackoverflow> SELECT * FROM stackoverflow.holidays ;
type | eventtime | beginend | name
------+-----------+----------+------
(0 rows)
Stop your node(s) properly (DISABLEGOSSIP, DRAIN, kill/stop, etc...).
Now, find the location of the old and new table on disk, and copy/move the files to the new location (from the old location):
$ ls -al /var/lib/cassandra/data22/stackoverflow/holidays-77a767e0a5f111e6a2bebd9d201c4c8f/
total 12
drwxrwxr-x 3 aploetz aploetz 4096 Nov 8 14:25 .
drwxrwxr-x 17 aploetz aploetz 4096 Nov 8 14:25 ..
drwxrwxr-x 2 aploetz aploetz 4096 Nov 8 14:25 backups
$ cp /var/lib/cassandra/data22/presentation/holidays-74bcfde0139011e6a67c2575e6398503/la* /var/lib/cassandra/data22/stackoverflow/holidays-77a767e0a5f111e6a2bebd9d201c4c8f/
$ ls -al /var/lib/cassandra/data22/stackoverflow/holidays-77a767e0a5f111e6a2bebd9d201c4c8f/
drwxrwxr-x 3 aploetz aploetz 4096 Nov 8 14:26 .
drwxrwxr-x 17 aploetz aploetz 4096 Nov 8 14:25 ..
drwxrwxr-x 2 aploetz aploetz 4096 Nov 8 14:25 backups
-rw-rw-r-- 1 aploetz aploetz 43 Nov 8 14:26 la-1-big-CompressionInfo.db
-rw-rw-r-- 1 aploetz aploetz 628 Nov 8 14:26 la-1-big-Data.db
-rw-rw-r-- 1 aploetz aploetz 9 Nov 8 14:26 la-1-big-Digest.adler32
-rw-rw-r-- 1 aploetz aploetz 16 Nov 8 14:26 la-1-big-Filter.db
-rw-rw-r-- 1 aploetz aploetz 57 Nov 8 14:26 la-1-big-Index.db
-rw-rw-r-- 1 aploetz aploetz 4468 Nov 8 14:26 la-1-big-Statistics.db
-rw-rw-r-- 1 aploetz aploetz 94 Nov 8 14:26 la-1-big-Summary.db
-rw-rw-r-- 1 aploetz aploetz 94 Nov 8 14:26 la-1-big-TOC.txt
-rw-rw-r-- 1 aploetz aploetz 43 Nov 8 14:26 la-2-big-CompressionInfo.db
-rw-rw-r-- 1 aploetz aploetz 164 Nov 8 14:26 la-2-big-Data.db
-rw-rw-r-- 1 aploetz aploetz 10 Nov 8 14:26 la-2-big-Digest.adler32
-rw-rw-r-- 1 aploetz aploetz 16 Nov 8 14:26 la-2-big-Filter.db
-rw-rw-r-- 1 aploetz aploetz 26 Nov 8 14:26 la-2-big-Index.db
-rw-rw-r-- 1 aploetz aploetz 4460 Nov 8 14:26 la-2-big-Statistics.db
-rw-rw-r-- 1 aploetz aploetz 108 Nov 8 14:26 la-2-big-Summary.db
-rw-rw-r-- 1 aploetz aploetz 94 Nov 8 14:26 la-2-big-TOC.txt
Restart your node(s).
Query via cqlsh:
Connected to SnakesAndArrows at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 2.2.8 | CQL spec 3.3.1 | Native protocol v4]
Use HELP for help.
aploetz@cqlsh> SELECT * FROM stackoverflow.holidays ;
type | eventtime | beginend | name
--------------+--------------------------+----------+------------------------
Religious | 2016-12-26 05:59:59+0000 | E | Christmas
Religious | 2016-12-25 06:00:00+0000 | B | Christmas
Religious | 2016-03-28 04:59:59+0000 | E | Easter
Religious | 2016-03-27 05:00:00+0000 | B | Easter
presentation | 2016-05-06 20:40:08+0000 | B | my presentation
presentation | 2016-05-06 20:40:03+0000 | B | my presentation
presentation | 2016-05-06 20:39:15+0000 | B | my presentation
presentation | 2016-05-06 20:38:10+0000 | B | my presentation
US | 2016-07-05 04:59:59+0000 | E | 4th of July
US | 2016-07-04 05:00:00+0000 | B | 4th of July
US | 2016-05-09 04:59:59+0000 | E | Mothers Day
US | 2016-05-08 05:00:00+0000 | B | Mothers Day
Nerd | 2016-12-22 05:59:59+0000 | E | 2112 Day
Nerd | 2016-12-21 06:00:00+0000 | B | 2112 Day
Nerd | 2016-09-26 04:59:59+0000 | E | Hobbit Day
Nerd | 2016-09-25 05:00:00+0000 | B | Hobbit Day
Nerd | 2016-09-20 04:59:59+0000 | E | Talk Like a Pirate Day
Nerd | 2016-09-19 05:00:00+0000 | B | Talk Like a Pirate Day
Nerd | 2016-05-07 04:59:59+0000 | E | Star Wars Week
Nerd | 2016-05-04 05:00:00+0000 | B | Star Wars Week
Nerd | 2016-03-14 05:00:00+0000 | E | Pi Day
Nerd | 2016-03-14 05:00:00+0000 | B | Pi Day
(22 rows)
The problem with this approach, is that you will need to stop the cluster, and move files around on each node. Whereas cqlsh COPY
would allow you to import and export on a single node, with the cluster still running.
And I know that COPY
has this reputation that limits it to smaller datasets. But 2.2.x has options that help throttle COPY to keep it from timing out on large datasets. I recently got it export/import 370 million rows without a timeout.
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