jiayuasu commented on code in PR #10981: URL: https://github.com/apache/iceberg/pull/10981#discussion_r1725529939
########## format/spec.md: ########## @@ -1407,3 +1432,9 @@ Iceberg supports two types of histories for tables. A history of previous "curre might indicate different snapshot IDs for a specific timestamp. The discrepancies can be caused by a variety of table operations (e.g. updating the `current-snapshot-id` can be used to set the snapshot of a table to any arbitrary snapshot, which might have a lineage derived from a table branch or no lineage at all). When processing point in time queries implementations should use "snapshot-log" metadata to lookup the table state at the given point in time. This ensures time-travel queries reflect the state of the table at the provided timestamp. For example a SQL query like `SELECT * FROM prod.db.table TIMESTAMP AS OF '1986-10-26 01:21:00Z';` would find the snapshot of the Iceberg table just prior to '1986-10-26 01:21:00 UTC' in the snapshot logs and use the metadata from that snapshot to perform the scan of the table. If no snapshot exists prior to the timestamp given or "snapshot-log" is not populated (it is an optional field), then systems should raise an informative error message about the missing metadata. + +## Appendix G: Geospatial Notes + +The Geometry class hierarchy and WKB serialization is defined by [OpenGIS Implementation Specification for Geographic information – Simple feature access – Part 1: Common architecture, Version 1.2.1](https://portal.ogc.org/files/?artifact_id=25355), from [Open Geospatial Consortium](https://www.ogc.org/standard/sfa/). Review Comment: We can borrow a more formal definition from GeoParquet spec > The preferred option for maximum portability is "WKB", signifying [Well Known Binary](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary). This SHOULD be the ["OpenGIS® Implementation Specification for Geographic information - Simple feature access - Part 1: Common architecture"](https://portal.ogc.org/files/?artifact_id=18241) WKB representation (using codes for 3D geometry types in the [1001,1007] range). This encoding is also consistent with the one defined in the ["ISO/IEC 13249-3:2016 (Information technology - Database languages - SQL multimedia and application packages - Part 3: Spatial)"](https://www.iso.org/standard/60343.html) standard. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
