Fokko commented on code in PR #8982:
URL: https://github.com/apache/iceberg/pull/8982#discussion_r1673855957
##########
format/spec.md:
##########
@@ -1370,3 +1370,16 @@ Writing v2 metadata:
* `sort_columns` was removed
Note that these requirements apply when writing data to a v2 table. Tables
that are upgraded from v1 may contain metadata that does not follow these
requirements. Implementations should remain backward-compatible with v1
metadata requirements.
+
+## Appendix F: Implementation Notes
+
+This section covers topics not required by the specification but
recommendations for systems implementing the Iceberg specification
+to help maintain a uniform experience.
+
+### Point in Time Reads (Time Travel)
+
+Iceberg supports two types of histories for tables. A history of previous
"current snapshots" stored in ["snapshot-log" table
metadata](#table-metadata-fields) and [parent-child lineage stored in
"snapshots"](#table-metadata-fields). These two histories
+might indicate different snapshot IDs for a specific timestamp. The
discrepencies can be caused by a variety of table operations (e.g. branch-merge
table workflows or forcing the current state of table to specific snapshot ID).
Review Comment:
I think this explains it all (to me at least :), after reading the comment
https://github.com/apache/iceberg/pull/5364#issuecomment-1227902420:
```suggestion
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` of the table).
```
##########
format/spec.md:
##########
@@ -1370,3 +1370,16 @@ Writing v2 metadata:
* `sort_columns` was removed
Note that these requirements apply when writing data to a v2 table. Tables
that are upgraded from v1 may contain metadata that does not follow these
requirements. Implementations should remain backward-compatible with v1
metadata requirements.
+
+## Appendix F: Implementation Notes
+
+This section covers topics not required by the specification but
recommendations for systems implementing the Iceberg specification
+to help maintain a uniform experience.
+
+### Point in Time Reads (Time Travel)
+
+Iceberg supports two types of histories for tables. A history of previous
"current snapshots" stored in ["snapshot-log" table
metadata](#table-metadata-fields) and [parent-child lineage stored in
"snapshots"](#table-metadata-fields). These two histories
+might indicate different snapshot IDs for a specific timestamp. The
discrepencies can be caused by a variety of table operations (e.g. branch-merge
table workflows or forcing the current state of table to specific snapshot ID).
Review Comment:
I think this explains it all (to me at least :), after reading the comment
on PR https://github.com/apache/iceberg/pull/5364#issuecomment-1227902420:
```suggestion
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` of the table).
```
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