Feature: Add Data Types to Support Postgres Migrations Better

[inviscid]

Support Common Datatypes as Aliases or Real

For the most part, migrating from Postgres based syntax to Databend has been pretty straightforward, however there are three data types that would be ideal to support.

UUID - This could be an Alias of STRING but it would be very helpful to have the dtype return as a UUID rather than STRING
DATE - This differs from TIMESTAMP in that all the time information is dropped
TIME - This also differs from TIMESTAMP by truncating the date information

Why separate DATE and TIME types when TIMESTAMP can hold the information? While we have been able to work around storing DATE and TIME information in a TIMESTAMP field, the problem arises when trying to perform operations (add, subtract, etc...) when the value stored contains extraneous information. Unless the user knows how the underlying data is stored they will get unexpected answers. This is obviously less than ideal.