Bootstrap init store.

CheckStorage verifies scdb storage is valid.

NeedBootstrap checks if the store is empty.

NewMemoryStorage inits a in memory storage use it only for testing.

Get All view names in database `dbName`.

AllDBPrivs is all the privileges in database scope in scdb.

AllGlobalPrivs is all the privileges in global scope in scdb.

AllTablePrivs is all the privileges in table scope in scdb.

VisibilityPrivColName is the privilege to scdb.tables_priv and scdb.columns_priv table column name.

Column Table stores the columns of a table `CREATE TABLE` statement will add some rows in this table This table mimics `information_schema.columns` in MySQL.

ColumnPriv Table stores the metadata of a column level user privilege.

Database Table stores the metadata of a database.

DatabasePriv Table stores the metadata of a database level user privilege.

DDLHandler handles DDL.

Table Table stores the metadata of a table.

TablePriv Table stores the metadata of a table level user privilege.

User Table stores the metadata of a user.

DDL is responsible for updating schema in data store and maintaining in-memory InfoSchema cache.