r2dbc-pool | Connection Pooling for Reactive Relational Database | Database library

Answering my own question.

TLDR

• Having org.springframework.boot:spring-boot-starter-data-r2dbc:2.3.5.RELEASE is enough to have connection pooling enabled by default
• No need to add io.r2dbc:r2dbc-postgresql explicitly
• No need to put :pool: in the URL in this case

Some detailed findings. it seems there are two ways to enable connection pool:

1. Put :pool: driver chunk into the URL and then io.r2dbc.pool.PoolingConnectionFactoryProvider#create will take care of creating a Connection Pool. This is described at https://github.com/r2dbc/r2dbc-pool#getting-started
2. Do not have spring.r2dbc.pool.enabled=false in configs (meaning that its absence is interpreted as true by default). This way a Connection Pool will be created by the org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryConfigurations.Pool#connectionFactory. I am not sure, but it looks like a generalized Spring Boot configuration-style override over a library specific :pool: option.

This options are independent and partly overlap and the second one takes precedence.

The second component evaluates also presence of the :pool: in the URL (see org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryConfigurations.PooledConnectionFactoryCondition) and if found it delegates the creation of the Connection Pool to the first one.

There is also a peculiar conclusion - having explicit spring.r2dbc.pool.enabled=false leads to creation of a Connection Pool anyway if there is a :pool: in the URL. Therefore the only way to disable pooling is to have spring.r2dbc.pool.enabled=false and to omit :pool: in the URL at the same time.