I am trying to export data from cassandra using CQL client. A column family has about 100000 rows in it. when i am copying dta into csv file using COPY TO command i get following rpc_time out error.
copy mycolfamily to '/root/mycolfamily.csv'
Request did not complete within rpc_timeout.
I am running in:
[cqlsh 3.1.6 | Cassandra 1.2.8 | CQL spec 3.0.0 | Thrift protocol 19.36.0]
How can I increase RPC timeout limit?
I tried adding rpc_timeout_in_ms: 20000 (defalut is 10000) in my conf/cassandra.yaml file. but while restarting cassandra I get:
[root#user ~]# null; Can't construct a java object for tag:yaml.org,2002:org.apache.cassandra.config.Config; exception=Cannot create property=rpc_timeout_in_ms for JavaBean=org.apache.cassandra.config.Config#71bfc4fc; Unable to find property 'rpc_timeout_in_ms' on class: org.apache.cassandra.config.Config
Invalid yaml; unable to start server. See log for stacktrace.
The COPY command currently does the same thing with SELECT with LIMIT 99999999. So, it will eventually goes to timeout while your data is growing. Here's the export function;
https://github.com/apache/cassandra/blob/trunk/bin/cqlsh#L1524
I'm doing the same export on production. What I'm doing is the following;
make select * from table where timeuuid = someTimeuuid limit 10000
write the result set to a csv file w/ >> mode
make the next selects with respect to the last timeuuid
You can pipe command in cqlsh by the following cqlsh command
echo "{$cql}" | /usr/bin/cqlsh -u user -p password localhost 9160 > file.csv
You can use Auto pagination by specifying fetch size in Datastax Java driver.
Statement stmt = new SimpleStatement("SELECT id FROM mycolfamily;");
stmt.setFetchSize(500);
session.execute(stmt);
for (Row r:result.all()){
//write to file
}
I have encountered the same problem a few minutes ago then I have found CAPTURE and it worked:
First start capturing on cqlsh and then run your query with some limiting of your choice.
http://www.datastax.com/documentation/cql/3.0/cql/cql_reference/capture_r.html
The best way yo export the data is using nodetool snapshot option. This returns immediately and can be restored later on. The only issue is that this export is per node and for the entire cluster.
Example:
nodetool -h localhost -p 7199 snapshot
See reference:
http://docs.datastax.com/en/archived/cassandra/1.1/docs/backup_restore.html#taking-a-snapshot
Related
I try to load with dsbulk a huge amount of data into a table wit a set using:
dsbulk load test.json \
-h cassandra-db -u ... -p ... -k mykeyspace \
-query "update mykeyspace.mytable set value_s = value_s +{:value_s} where value_1=:value_1 and value_2=:value_2"
I get the following error:
Operation LOAD_20220629-122020-418911 failed: Invalid set literal for value_s: bind variables are not supported inside collection literals
If I use
-query "update mykeyspace.mytable set value_s = value_s +{'mystaticvalue'} where value_1=:value_1 and value_2=:value_2"
the load is executed as expected. Anyone an idea how I can parameterize my set svalue?
Alternatively, I can create individual update statements, which I then execute via the cqlsh. Unfortunately the processing time is really slow. I have > 1 billion records to insert.
Unfortunately, Cassandra does not allow the use of bind variables when updating CQL collections. As a result, you won't be able to do it with the Bulk Loader either. Cheers!
When i connect to my databse via phpmyadmin everything works fine and it shows me the data.
When i am on my server i can see all data and work with it.
But when i try to connect to my server i'm getting this error:
com.mysql.cj.jdbc.exceptions.PacketTooBigException: Packet for query is too large (4.739.923 > 65.535). You can change this value on the server by setting the 'max_allowed_packet' variable.
im getting the max allowed packet size here:
Database changed
MariaDB [selforder]> SELECT ##max_allowed_packet;
+----------------------+
| ##max_allowed_packet |
+----------------------+
| 536870912 |
+----------------------+
1 row in set (0.00 sec)
and i changed my file nano /root/.my.cnf to this:
[mysqld]
max_allowed_packet=536870912
but i still get this error;
not really an answer but my problem was, that i installed multiple versions of mysql, i completly reinstalled my system
I am trying to alter my cassandra tables starting with a specific name.
My table starts with sample_1,sample_2,sample_13567,sample_adgf and so on...
The table names are random but starting with same prefix.
I want to add a new column to all these tables.
Can some one suggest me the update query using the regex for table names.
If you are using linux You can this in two step :
First Generate all alter command into a file like below :
for i in {1..13567}; do echo "ALTER TABLE sample_$i ADD test text;"; done > alter.cql
The above command will create alter command to add test text column for table sample_1 to sample_13567 and store into a file alter.cql
Now you can just load the cql file into cqlsh like below :
cqlsh 127.0.0.1 -u cassandra -p cassandra -k ashraful_test -f alter.cql
Here
-u username
-p password
-k keyspace_name
-f file name to load
By the way having too much table is not a good idea.
Check this link https://stackoverflow.com/a/33389204/2320144
$describe = new Cassandra\SimpleStatement(<<<EOD
describe keyspace.tablename
EOD
);
$session->execute($describe);
i used above code but it is not working.
how can i fetch field name and it's data type from Cassandra table ?
Refer to CQL documentation. Describe expects a table/schema/keyspace.
describe table keyspace.tablename
Its also a cqlsh command, not an actual cql command. To get this information query the system tables. try
select * from system.schema_columns;
- or for more recent versions -
select * from system_schema.columns ;
if using php driver may want to check out http://datastax.github.io/php-driver/features/#schema-metadata
Try desc table keyspace.tablename;
I'm looking for a way to delete all of the rows from a given column family in cassandra.
This is the equivalent of TRUNCATE TABLE in SQL.
You can use the truncate thrift call, or the TRUNCATE <table> command in CQL.
http://www.datastax.com/docs/1.0/references/cql/TRUNCATE
You can also do this via Cassandra CQL.
$ cqlsh
Connected to Test Cluster at localhost:9160.
[cqlsh 4.1.1 | Cassandra 2.0.6 | CQL spec 3.1.1 | Thrift protocol 19.39.0]
Use HELP for help.
cqlsh> TRUNCATE my_keyspace.my_column_family;
Its very simple in Astyanax. Just a Single Line statement
/* keyspace variable is Keyspace Type */
keyspace.truncateColumnFamily(ColumnFamilyName);
If you are using Hector it is easy as well:
cluster.truncate("our keyspace name here", "your column family name here");
If you are using cqlsh, then you can either do it in 2 ways
use keyspace; and then truncate column_family;
truncate keyspace.column_family;
If you want to use DataStax Java driver, you can look at -
http://www.datastax.com/drivers/java/1.0/com/datastax/driver/core/querybuilder/QueryBuilder.html
or
http://www.datastax.com/drivers/java/2.0/com/datastax/driver/core/querybuilder/Truncate.html
depending on your version.
if you are working on cluster setup, truncate can only be used when all the nodes of the cluster are UP.
By using truncate, we will miss the data(we are not sure with the importance of the data)
So the very safe way as well a trick to delete data is to use COPY command,
1) backup data using copy cassandra cmd
copy tablename to 'path'
2) duplicate the file using linux cp cmd
cp 'src path' 'dst path'
3) edit duplicate file in dst path, delete all lines expect first line.
save the file.
4) use copy cassandra cmd to import
copy tablename from 'dst path'