Best practices for schema management

Here are several best practices to follow. They'll help make your management commands work better, and have a lighter impact on the service resources.

Action	Use	Don't use	Notes
Create multiple tables	Use a single .create tables command	Don't issue many .create table commands
Rename multiple tables	Make a single call to .rename tables	Don't issue a separate call for each pair of tables
Show commands	Use the lowest-scoped .show command	Don't apply filters after a pipe (|)	Limit use as much as possible. When possible, cache the information they return.
Show extents	Use .show table T extents	Don't use .show cluster extents | where TableName == 'T'
Show database schema.	Use .show database DB schema	Don't use .show schema | where DatabaseName == 'DB'
Show schema on a cluster which a large schema	Use .show databases schema	Don't use .show schema	For example, use on cluster with more than 100 databases.
Check a table's existence or get the table's schema	Use .show table T schema as json	Don't use .show table T	Only use this command to get actual statistics on a single table.
Define the schema for a table that will include datetime values	Set the relevant columns to the datetime type	Don't convert string or numeric columns to datetime at query time for filtering, if that can be done before or during ingestion time
Add extent tag to metadata	Use sparingly	Avoid drop-by: tags, which limit the system's ability to do performance-oriented grooming processes in the background.	See performance notes.