![\"Cassandra\"](\"https:\/\/ikriv.com\/blog\/wp-content\/uploads\/2023\/07\/cassandra.png\")
<\/p>\n<\/p>\n
Last week I had an opportunity to experiment with Cassandra database in a semi-real environment.<\/p>\n
A few notes:<\/p>\n
CREATE TABLE IF NOT EXISTS test.data (\r\n channel text,\r\n subdomain text,\r\n data_center text,\r\n day date, \/\/ we need this to limit the partition size\r\n message_id timeuuid,\r\n tags map<text,text>,\r\n sender_id text,\r\n sequence_number bigint,\r\n sent_at timestamp,\r\n received_at timestamp,\r\n header blob,\r\n payload blob,\r\n \/\/ the stuff in the inner parens is the partition key; the rest is the clustering (sorting) key\r\n PRIMARY KEY ((channel, subdomain, data_center, day), sent_at, message_id)\r\n)\r\nWITH CLUSTERING ORDER BY (sent_at ASC, message_id ASC);<\/code><\/pre>\nContrast it with Amazon DynamoDB that insists that both partition key and clustering key be strings with all the parts squished together as in InvoiceNumber#121212#0<\/code>.<\/p>\nA few more things to note:<\/p>\n
\n- I was able to insert ~90,000 records per second using multiple processes, with the client and the server on the same machine, and each record being slightly over 1KB.<\/li>\n
- When creating a new index, Cassandra will return right away, but will not allow to query the table for a while, presumably until the index has been built.<\/li>\n
- Some queries that go cross partition are allowed, e.g.\n
\n- SELECT * FROM table [LIMIT N] or<\/li>\n
- SELECT COUNT(*) from table.<\/li>\n<\/ul>\n<\/li>\n
- The latter tends to time out when the table reaches a few million records.<\/li>\n<\/ul>\n
Generally, inability to find the size of the table is annoying. There is a tool called nodetool that would return statistics, but the number of records is not part of that statistics unfortunately.<\/p>\n
I operated with a single-node setup, and did not have an opportunity to explore replication, quorum and the like, this would be the subject of another excercise I suppose.<\/p>\n","protected":false},"excerpt":{"rendered":"