JanKaul commented on code in PR #11041: URL: https://github.com/apache/iceberg/pull/11041#discussion_r2797146438
########## format/view-spec.md: ########## @@ -160,6 +176,109 @@ Each entry in `version-log` is a struct with the following fields: | _required_ | `timestamp-ms` | Timestamp when the view's `current-version-id` was updated (ms from epoch) | | _required_ | `version-id` | ID that `current-version-id` was set to | +#### Storage Table Identifier + +The table identifier for the storage table that stores the precomputed results. + +| Requirement | Field name | Description | +|-------------|----------------|-------------| +| _required_ | `namespace` | A list of strings for namespace levels | +| _required_ | `name` | A string specifying the name of the table | + +### Storage table metadata + +This section describes additional metadata for the storage table that supplements the regular table metadata and is required for materialized views. +The property "refresh-state" is set on the [snapshot summary](https://iceberg.apache.org/spec/#snapshots) property of every storage table snapshot to determine the freshness of the precomputed data of the storage table. + +| Requirement | Field name | Description | +|-------------|-----------------|-------------| +| _required_ | `refresh-state` | A [refresh state](#refresh-state) record stored as a JSON-encoded string | + +#### Freshness + +A materialized view is "fresh" when the storage table adequately represents the logical query definition of the view. +Since different systems define freshness differently, it is left to the consumer to evaluate freshness based on its own policy. + +**Consumer behavior:** + +When evaluating freshness, consumers: +- May apply time-based freshness policies, such as allowing a staleness window based on `refresh-start-timestamp-ms`. +- May compare the `source-states` list against the states loaded from the catalog to verify the producer's freshness interpretation. +- May parse the view definition to implement more sophisticated policies. +- When a materialized view is considered stale, can fail, refresh inline, or treat the materialized view as a logical view. +- Should not consume the storage table as it is when the materialized view doesn't meet the freshness criteria. + +**Producer behavior:** + +Producers should provide the necessary information in the [refresh state](#refresh-state) such that consumers can verify the logical equivalence of the precomputed data with the query definition. +Different producers may have different freshness interpretations, based on how much of the dependency graph must be current. +Some require the entire query tree to be fully up to date, while others only require direct children or leaf nodes. + +When writing the refresh state, producers: +- Should provide a sufficient list of source states such that consumers can determine freshness according to the producer's interpretation. +- May leave the source states list empty if the source state cannot be determined for all objects (for example, for non-Iceberg tables). +- Must store the entry with the oldest snapshot-id or version-id when the same source object is reachable through multiple paths in the dependency graph (diamond dependency pattern). + +#### Refresh state + +The refresh state record captures the dependencies in the materialized view's dependency graph. +These dependencies include source Iceberg tables, views, and nested materialized views. + +The refresh state has the following fields: + +| Requirement | Field name | Description | +|-------------|----------------|-------------| +| _required_ | `view-version-id` | The `version-id` of the materialized view when the refresh operation was performed | +| _required_ | `source-states` | A list of [source states](#source-state) records | +| _required_ | `refresh-start-timestamp-ms` | A timestamp of when the refresh operation was started | + +#### Source state + +Source state records capture the state of objects referenced by a materialized view. +Each record has a `type` field that determines its form: + +| Type | Description | +|---------|-------------| +| `table` | An Iceberg table, including storage tables of nested materialized views | +| `view` | An Iceberg view, including nested materialized views | + +Source materialized views are represented by two source state entries: one for the view itself and one for its storage table. Review Comment: I think the binding is not strictly required as all entities have to be fetched from the catalog to get their snapshot-ids/version-ids. At that point the binding is clear. -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
