Overview

Why do auto-increment columns not work in sharded Vitess?

Auto-increment columns do not work very well for sharded tables. Vitess sequences solve this problem. Sequence tables must be specified in the VSchema and then tied to table columns. At the time of insert, if no value is specified for such a column, VTGate ...more

What is resharding? How does it work?

Vitess supports resharding, in which the number of shards is changed on a live cluster. This can be either splitting one or more shards into smaller pieces, or merging neighboring shards into bigger pieces. During resharding, the data in the source shards ...more

How are shards named?

Shard names have the following characteristics: They represent a range, where the left number is included, but the right is not. Their notation is hexadecimal. They are left justified. A - prefix means: anything less than the RHS value. A - postfix means: ...more

What does “/0” or “/-”mean?

0 or - indicates that the keyspace in question is unsharded. This means that a single shard covers the entire keyrange. Note that while both 0 and - are supported for legacy reasons, you can’t merge into shard 0 only -. For this and other reasons, it is ...more