CODEWITHSUNDEEP
cassandra
KTBFFH
KTBFFH

Reputation: 65

Cassandra OperationTimedOut

select count (*) from my_table gives me OperationTimedOut: errors={}, last_host=127.0.0.1

I have already tried to change the values in request_timeout_in_ms in cassandra.yaml and request_timeout in cqlshrc.sample. (Both are in C:\Programs\DataStax-DDC\apache-cassandra\conf) But without success.

How can I increse timeout?

Upvotes: 0

Views: 276

Answers (1)

yurgis
yurgis

Reputation: 4067

select count (*) is not doing what you think. It is actually expensive as it counts the rows one by one. You can track number of records using a separate column family with a counter, which you will need to increment for every insert you do into your table. For example

CREATE TABLE IF NOT EXISTS my_table_counter (
  mykey text,
  count counter, 
  PRIMARY KEY (mykey)
);

Then for every insert into your table, do counter update:

INSERT into my_table (mykey, mydata) VALUES (?, ?);
UPDATE my_table_counter SET count = count + 1 WHERE mykey = ?;

To get the count:

SELECT count FROM my_table_counter WHERE mykey = ?

Note that counters are not idempotent, so in a rare event of a failure your data might be under or over-counted. Also the code above assumes that you only insert with a new key.

If you need a precise counting, Cassandra may be not a good fit for that. Also if you are not inserting with unique keys you may need to consider using light weight transaction with insert (IF NOT EXISTS) and update a counter only if transaction was applied.

Upvotes: 1

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