Trino Iceberg Timestamp with Timezone Query Rendering/Display Enhancment about trino HOT 1 OPEN

In Trino, timestamp with time zone is rendered with it's stored time zone. This is intentional, as the insertion time zone is considered to have meaning. Readers can choose to render it in a different time zone via at time zone. The session time zone is used for conversions between timestamp and timestamp with time zone inside the query engine, as described by the SQL specification.

There are roughly three phases of processing when reading timestamp values that need to be considered:

• Internal representation after value is read from storage
• How the value is transported to the client
• Rendering the value to the user

Changing the representation after the value is read from storage is problematic. It makes it impossible to observe the value as it was stored, with its original time zone. Changing the representation when the value is transported to the client requires changes to the protocol to allow clients to express such preference. Adjusting the rendering in the client requires each client to be able to do so independently.

As an aside, Iceberg's timestamp with time zone type is stored in UTC, and the timezone information is lost. From the Iceberg spec (https://iceberg.apache.org/spec/#primitive-types):

Timestamp values with time zone represent a point in time: values are stored as UTC and do not retain a source time zone (2017-11-16 17:10:34 PST is stored/retrieved as 2017-11-17 01:10:34 UTC and these values are considered identical).

from trino.