Limits in Azure Database for PostgreSQL - Single Server

The following sections describe capacity and functional limits in the database service. If you'd like to learn about resource (compute, memory, storage) tiers, see the pricing tiers article.

Maximum connections

The maximum number of connections per pricing tier and vCores are shown below. The Azure system requires five connections to monitor the Azure Database for PostgreSQL server.

Pricing Tier vCore(s) Max Connections Max User Connections
Basic 1 55 50
Basic 2 105 100
General Purpose 2 150 145
General Purpose 4 250 245
General Purpose 8 480 475
General Purpose 16 950 945
General Purpose 32 1500 1495
General Purpose 64 1900 1895
Memory Optimized 2 300 295
Memory Optimized 4 500 495
Memory Optimized 8 960 955
Memory Optimized 16 1900 1895
Memory Optimized 32 1987 1982

When connections exceed the limit, you may receive the following error:

FATAL: sorry, too many clients already

Important

For best experience, we recommend that you use a connection pooler like pgBouncer to efficiently manage connections.

A PostgreSQL connection, even idle, can occupy about 10MB of memory. Also, creating new connections takes time. Most applications request many short-lived connections, which compounds this situation. The result is fewer resources available for your actual workload leading to decreased performance. A connection pooler that decreases idle connections and reuses existing connections will help avoid this. To learn more, visit our blog post.

Functional limitations

Scale operations

  • Dynamic scaling to and from the Basic pricing tiers is currently not supported.
  • Decreasing server storage size is currently not supported.

Server version upgrades

  • Automated migration between major database engine versions is currently not supported. If you would like to upgrade to the next major version, take a dump and restore it to a server that was created with the new engine version.

Note that prior to PostgreSQL version 10, the PostgreSQL versioning policy considered a major version upgrade to be an increase in the first or second number (for example, 9.5 to 9.6 was considered a major version upgrade). As of version 10, only a change in the first number is considered a major version upgrade (for example, 10.0 to 10.1 is a minor version upgrade, and 10 to 11 is a major version upgrade).

VNet service endpoints

  • Support for VNet service endpoints is only for General Purpose and Memory Optimized servers.

Restoring a server

  • When using the PITR feature, the new server is created with the same pricing tier configurations as the server it is based on.
  • The new server created during a restore does not have the firewall rules that existed on the original server. Firewall rules need to be set up separately for this new server.
  • Restoring a deleted server is not supported.

UTF-8 characters on Windows

  • In some scenarios, UTF-8 characters are not supported fully in open source PostgreSQL on Windows, which affects Azure Database for PostgreSQL. Please see the thread on Bug #15476 in the postgresql-archive for more information.

GSS error

If you see an error related to GSS, you are likely using a newer client/driver version which Azure Postgres Single Server does not yet fully support. This error is known to affect JDBC driver versions 42.2.15 and 42.2.16.

  • We plan to complete the update by the end of November. Consider using a working driver version in the meantime.
  • Or, consider disabling the GSS request. Use a connection parameter like gssEncMode=disable.

Next steps