CheckColumns will return a non-nil error if one or more columns from cols is missing from the underlying struct.

Columns returns all the struct table columns according to the 'db' and 'json' meta tag values.

MissingColumns returns a list of columns from cols that were not found in the provided struct.

MySQL is a convenience initializer to obtain a MySQL DB connection.

NewBatchLoader will create a BatchLoader.

Postgres is a convenience initializer to obtain a Postgres DB connection.

Values prepares a row insert for struct v for the provided columns.

BatchLoader implementations should have an initializer that also pings the db to check the connection.