About Can Sayn
Can Sayın is experienced Database Administrator in open source relational and NoSql databases, working in complicated infrastructures. Over 5 years industry experience, he gain managing database systems. He is working at ChistaDATA Inc. His areas of interest are generally on open source systems.
Contact: Website

Migration From MySql To ClickHouse

Transfer the data from MySQL into ClickHouse   Recommended solution – MinervaDB ClickHouse MySQL Data Reader (forked from Alitinity/clickhouse-mysql-data-reader ) GitHub – https://github.com/MinervaDB/MinervaDB-ClickHouse-MySQL-Data-Reader Installation and configuration   ** Prerequisites – we have to install pip3 […]

ClickHouse ATTACH Statement

Attaches a table or a dictionary, for example, when moving a database to another server. The query does not create data on the disk, but assumes that data is already in the appropriate places, and […]

Examining Errors Generated By ClickHouse

Log of query execution Controlled by session level setting send_logs_level Possible values: ‘trace’, ‘debug’, ‘information’, ‘warning’, ‘error’, ‘fatal’, ‘none’ Can be used with clickhouse-client in both interactive and non-interactive mode. clickhouse-client -mn –send_logs_level=’trace’ –query “SELECT sum(number) FROM numbers(1000)” Result; […]

Ingesting Data From MongoDB

In this article, you will learn how to read your data from ClickHouse which is stored in MongoDB. MongoDB engine is read-only table engine which allows to read data (SELECT queries) from remote MongoDB collection. Engine […]

Finding The Queries That Resulted In An Error

  In ClickHouse, there is a table called query_log which is located in system database. query_log table gives you information about all the queries running on the database. This is an useful option for troubleshooting […]

Materialised Views In ClickHouse

What is Materialized View | What should it mean to us? While normal views only store the queries and fetch the data from the related tables according to the specified criteria when requested, materialized views […]

ClickHouse KILL Statement

There are two kinds of kill statements: to kill a query and to kill a mutation. KILL QUERY Attempts to forcibly terminate the currently running queries. The queries to terminate are selected from the system.processes […]

ClickHouse Recommended Troubleshooting Metrics

Alert Name Shell or SQL command Severity ClickHouse status $ curl ‘http://localhost:8123/’ Ok. Critical Too many simultaneous queries. Maximum: 100 (by default) select value from system.metrics where metric=’Query’ Critical Replication status $ curl ‘http://localhost:8123/replicas_status’ Ok. […]

1 2 3 4