szehon-ho commented on code in PR #11041: URL: https://github.com/apache/iceberg/pull/11041#discussion_r1868399418
########## 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 that precompute the data from the view query. +When queried, materialized views return the precomputed data, 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, known as the storage table, which stores the precomputed data. +The metadata for a materialized view extends the common view metadata, adding a pointer to the precomputed data and refresh information to determine if the data is still fresh. +The refresh information is composed of data about the so-called "source tables", which are the 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 don't match, indicating that a refresh operation needs to be performed to capture the latest source table changes. Review Comment: nit: suggestion to avoid the contraction 'don't' in format spec -- 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
