The Schema protobuf message: Drizzle’s metadata on a schema

I’ve previously talked about table metadata in Drizzle and how we use the table protobuf message to describe a table (see Drizzle FRM Replacement and others). The model in Drizzle is that the engine is responsible for its metadata. For schemas (you may be thinking ‘database’ but we’re moving to the Schema terminology in Drizzle) we also have a small amount of metadata.

The protobuf message is specified in drizzled/message/schema.proto and is incredibly short. In fact, here it is in its entirety:

package drizzled.message;
option optimize_for = SPEED;
message Schema {
  required string name = 1;
  optional string collation = 2;

We don’t keep an awful lot of metadata about schemas. A Schema has a name and it has a default collation.

You can also read the db.opt file directly using the provided (and very simple) schema_reader utility.

In the near future, we could have CREATE DATABASE and CREATE SCHEMA replicated via this protobuf message. This would make it extremely easy to parse for utilities parsing the replication stream.

We’ll also (rather shortly) have key,value pairs for options to CREATE SCHEMA/CREATE DATABASE. More on that later :)

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