stevenzwu commented on code in PR #11041: URL: https://github.com/apache/iceberg/pull/11041#discussion_r2143429478
########## format/view-spec.md: ########## @@ -42,12 +42,28 @@ An atomic swap of one view metadata file for another provides the basis for maki Writers create view metadata files optimistically, assuming that the current metadata location will not be changed before the writer's commit. Once a writer has created an update, it commits by swapping the view's metadata file pointer from the base location to the new location. +### Materialized Views + +Materialized views are a type of view with precomputed results from the view query stored as a table. +When queried, engines may return the precomputed data for the materialized views, shifting the cost of query execution to the precomputation step. + +Iceberg materialized views are implemented as a combination of an Iceberg view and an underlying Iceberg table, the "storage-table", which stores the precomputed data. +Materialized View metadata is a superset of View metadata with an additional pointer to the storage table and refresh metadata. +Refresh metadata contains information about the "source tables", tables referenced in the query definition of the materialized view. +The storage table can be in the states of "fresh", "stale" or "invalid", which are determined from the following situations: +* **fresh** -- The `snapshot_id`s of the last refresh operation match the current `snapshot_id`s of the source tables. +* **stale** -- The `snapshot_id`s do not match, indicating that a refresh operation needs to be performed to capture the latest source table changes. +* **invalid** -- The current `version_id` of the materialized view does not match the `refresh-version-id` of the refresh state. + ## Specification ### Terms * **Schema** -- Names and types of fields in a view. * **Version** -- The state of a view at some point in time. +* **Storage table** -- Iceberg table that stores the precomputed data of the materialized view. +* **Source table** -- A table reference that occurs in the query definition of the materialized view. The materialized view depends on the data from the source tables. +* **Source view** -- A view reference that occurs in the query definition of the materialized view. The materialized view depends on the definitions from the source views. Review Comment: MV SQL can reference tables or views. They are called source tables or views. -- 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
