Meet SPQR 1.3.0

[Denchick]

It's been a long time since the last SPQR release, and a lot of work has been done. Here's a brief review of what we've been working on.

SPQR 2.0 news #431
In this release, we add new syntax to handle sharding configuration. To make all things work, you should create a distribution via CREATE DISTRIBUTION command. The next step is to specify a list of tables and columns via ATTACH RELATION command. At the end specify a list of ranges: which values to route to which shard via CREATE KEY RANGE command. You can see an example at Syntax.md. SHARDING RULE syntax is deprecated now.

Extended Protocol improvements
We continue to work on the extended protocol support in SPQR. A lot of work has already been done, and in most cases, the router works correctly.

Shards [re]balancing news
The essential part of our solution is smart shard rebalancing. We made the first version of this component (again). Data migration between shards aims to balance the workload across shards proportionally. The main idea is to minimize any locking impact during these migrations, which is accomplished by reducing the size of the data ranges being transferred.

We still have a lot of room for improvement. The full list of changes can be found in the release notes. Stay tuned!