Why did a column suddenly become TIMESTAMP instead of STRING?

FAQs
1

The engine now supports true timestamp inference.

When inferDatesAsTimestamp = true:

  • Sampled values are tested against common date/time formats

  • If all valid samples match date patterns, the column becomes TIMESTAMP

Supported formats include:

  • yyyy-MM-dd

  • dd/MM/yyyy

  • MM/dd/yyyy

  • yyyy-MM-dd HH:mm:ss

  • ISO date formats

When it does NOT happen

  • Mixed date and text values

  • Unparseable formats

  • Partial matches

In these cases, the column remains STRING.

Recommendation

Enable timestamp inference for analytics.
Enforce schema for reporting pipelines.