This series adds support for detecting collections that have too many items
and recording them in `system.large_cells`.
A configuration variable was added to db/config: `compaction_collection_items_count_warning_threshold` set by default to 10000.
Collections that have more items than this threshold will be warned about and will be recorded as a large cell in the `system.large_cells` table. Documentation has been updated respectively.
A new column was added to system.large_cells: `collection_items`.
Similar to the `rows` column in system.large_partition, `collection_items` holds the number of items in a collection when the large cell is a collection, or 0 if it isn't. Note that the collection may be recorded in system.large_cells either due to its size, like any other cell, and/or due to the number of items in it, if it cross the said threshold.
Note that #11449 called for a new system.large_collections table, but extending system.large_cells follows the logic of system.large_partitions is a smaller change overall, hence it was preferred.
Since the system keyspace schema is hard coded, the schema version of system.large_cells was bumped, and since the change is not backward compatible, we added a cluster feature - `LARGE_COLLECTION_DETECTION` - to enable using it.
The large_data_handler large cell detection record function will populate the new column only when the new cluster feature is enabled.
In addition, unit tests were added in sstable_3_x_test for testing large cells detection by cell size, and large_collection detection by the number of items.
Closes#11449Closes#11674
* github.com:scylladb/scylladb:
sstables: mx/writer: optimize large data stats members order
sstables: mx/writer: keep large data stats entry as members
db: large_data_handler: dynamically update config thresholds
utils/updateable_value: add transforming_value_updater
db/large_data_handler: cql_table_large_data_handler: record large_collections
db/large_data_handler: pass ref to feature_service to cql_table_large_data_handler
db/large_data_handler: cql_table_large_data_handler: move ctor out of line
docs: large-rows-large-cells-tables: fix typos
db/system_keyspace: add collection_elements column to system.large_cells
gms/feature_service: add large_collection_detection cluster feature
test: sstable_3_x_test: add test_sstable_too_many_collection_elements
test: lib: simple_schema: add support for optional collection column
test: lib: simple_schema: build schema in ctor body
test: lib: simple_schema: cql: define s1 as static only if built this way
db/large_data_handler: maybe_record_large_cells: consider collection_elements
db/large_data_handler: debug cql_table_large_data_handler::delete_large_data_entries
sstables: mx/writer: pass collection_elements to writer::maybe_record_large_cells
sstables: mx/writer: add large_data_type::elements_in_collection
db/large_data_handler: get the collection_elements_count_threshold
db/config: add compaction_collection_elements_count_warning_threshold
test: sstable_3_x_test: add test_sstable_write_large_cell
test: sstable_3_x_test: pass cell_threshold_bytes to large_data_handler
test: sstable_3_x_test: large_data_handler: prepare callback for testing large_cells
test: sstable_3_x_test: large_data tests: use BOOST_REQUIRE_[GL]T
test: sstable_3_x_test: test_sstable_log_too_many_rows: use tests::random
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