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92d03be37b
Sometimes a single modification to a base partition requires updates to a large number of view rows. A common example is deletion of a base partition containing many rows. A large BATCH is also possible. To avoid large allocations, we split the large amount of work into batch of 100 (max_rows_for_view_updates) rows each. The existing code assumed an empty result from one of these batches meant that we are done. But this assumption was incorrect: There are several cases when a base-table update may not need a view update to be generated (see can_skip_view_updates()) so if all 100 rows in a batch were skipped, the view update stopped prematurely. This patch includes two tests showing when this bug can happen - one test using a partition deletion with a USING TIMESTAMP causing the deletion to not affect the first 100 rows, and a second test using a specially-crafed large BATCH. These use cases are fairly esoteric, but in fact hit a user in the wild, which led to the discovery of this bug. The fix is fairly simple: To detect when build_some() is done it is no longer enough to check if it returned zero view-update rows; Rather, it explicitly returns whether or not it is done as an std::optional. The patch includes several tests for this bug, which pass on Cassandra, failed on Scylla before this patch, and pass with this patch. Fixes #12297. Signed-off-by: Nadav Har'El <nyh@scylladb.com> Closes #12305