One of the exciting things[1] about working on a storage engine in Drizzle is that you get to manage your own metadata. When the database engine you’re writing the storage engine interface for has a pretty complete data dictionary (e.g. Embedded InnoDB) you could just directly use it. At some point I plan to do this for the embedded_innodb engine for Drizzle so that you could just point Drizzle at an existing Embedded InnoDB database and run SQL queries on it.

The Drizzle table message does have some things in it that aren’t in the InnoDB data dictionary though (e.g. table and column comments). We want to preserve these (and also things like there may be several data types in Drizzle that map to the same data type in InnoDB). Since the Embedded InnoDB API allows us to do things within the DDL transaction (such …

If you’ve ever opened up drizzled/message/table.proto in the Drizzle source tree you will have seen what’s in the table message: the structure that describes a database table in Drizzle. Previously I’ve talked about the Table message more generally, giving a fair bit of history of the FRM file and how we’ve replaced it with both the Table protobuf message and an infrastructure inside Drizzle so that Storage Engines own their own metadata.

Yesterday I talked about the …