Change the default precision of timestamp to micros (6) as specified by SQL standard.

[amoghmargoor]

The default precision for timestamp was chosen as 3 and it was decided to make it 6 in future as specified by SQL standard as specified by comment here: #1284 (comment). Code link:

trino/core/trino-spi/src/main/java/io/trino/spi/type/TimestampType.java

Line 36 in 75854f4

public static final int DEFAULT_PRECISION = 3; // TODO: should be 6 per SQL spec

.

[amoghmargoor]

PR: #20290

[jkylling]

The Delta Lake connector is looking to make a similar change: #20359

[Samrose-Ahmed]

Why was the PR closed, interested in this as well for Iceberg.

[mosabua]

We will need to break this work down. The support for higher precision varies across data sources, and for table formats also depends on the file format, metastore and other factors.

As such we might have to figure out how to enable this on a fine-grained basis. Maybe per catalog with a catalog configuration property. And if we do a global configuration .. what do we do - fail queries?

Essentially this requires more thought and work before we can ship this, but to be clear. We do want to proceed.