Category Archives: Databases

How to choose a partition key for DynamoDB

Here’s an article about how to do it right: The main ideas — partition key should have a good cardinality, but at the same time it should be queried easily as all the queries to DynamoDB should start with PartitionKey=…, as they are hashes.

Checking restart problems with mysql on centos

You probable installed MySQL with a help of article like this — So your mysql is controlled by systemctl. Check current status — sudo systemctl status mysqld. Start service — sudo systemctl start mysqld Logs for systemctl are here — sudo journalctl -xe Logs for mysql can be found here — /var/log/mysqld.log. Configs are …

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DynamoDB videos list

AWS decided to start a series of videos on DynamoDB usage. First 5 episodes were published on Youtube, and I made a playlist for them:

Install postgresql 11 on CentOs7

Just what to do, no discussion.

Postgres in docker: random «unique violation» errors

While running postgres in docker (for development, of course), from time to time I just run into errors like «Duplicate Key Value Violates Unique Constraint». I found the solution (thanks to this answer, for sure — if you have a table called «[table]», just do this

Another cool article on using PostgreSQL+pgBouncer with go

Extremely interesting and very practical talk about problems occurring with go+pgBouncer (in Russian, sorry). And a video on that:

PgBouncer and prepared statements

In our system, we use connection pooler called PgBouncer as a proxy to PostgreSQL server. PgBouncer has two main modes Session pooling mode This mode is less performant (it’s a default mode). When a client connects, a server connection will be assigned to it for the whole duration it stays connected. So it does not …

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ORM for go Never used it as we always write SQL queries manually. But looks okay for ORM (well, actually a query-builder).

PostgreSQL: TOP slow queries

Golang, PostgreSQL and array_agg

If you have SQL like this: