Release proposal: Nightly v0.5

[BohuTANG]

Hi All!

After about six months of development, it is time to release the nightly v0.5 🎉 , please leave any questions, comments, and concerns.

What's Databend release channels?

Databend release process following the 'release train' model used by e.g. Rust, Firefox and Chrome, as well as 'feature staging'.

But in the early stage Databend will upgrade the nightly version number only, and when a nightly version is ready for beta, we will leave a beta version getting off of the nightly version.

Ok, Let's start by understanding how Databend do the releases.
The following is mainly from the Rust documentation How Rust is Made and “Nightly Rust”.

There are three release channels for Databend(this is same as Rust):

• Nightly
• Beta
• Stable

So as time passes, our releases look like this, once a night:

nightly: * - - * - - *

Every six weeks, it’s time to prepare a new release! The beta branch of the Databend repository branches off from the main branch used by nightly. Now, there are two releases:

nightly: * - - * - - *
                     |
beta:                *

Six weeks after the first beta was created, it’s time for a stable release! The stable branch is produced from the beta branch:

nightly: * - - * - - * - - * - - * - - * - * - *
                     |
beta:                * - - - - - - - - *
                                       |
stable:                                *

This is called the “train model” because every six weeks, a release “leaves the station”, but still has to take a journey through the beta channel before it arrives as a stable release.

What Databend nightly v0.5 can do?

• You can deploy Databend locally with BendCtl (TODO: the guideline)
• You can experience queries with some dataset (like OnTime).

What Databend nightly v0.5 can NOT do?

• Not ready for performance benchmark
• Not ready for join query
• Not ready for cloud storage
• Not ready for production

What Databend nightly v0.6 can do?

• Checklist proposal: Nightly v0.6

Notes

Nightly v0.5 is part of our Roadmap 2021
Community website: https://databend.rs

[BohuTANG]

Update:
There are still some tasks that need to be done or improved before v0.5 released:
fuse table(#2355 )

[BohuTANG]

Genesis version is out:
https://github.com/datafuselabs/databend/releases/tag/v0.5.0-nightly