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ce00d61917
Replace the physical system.large_partitions, system.large_rows, and system.large_cells CQL tables with virtual tables that read from LargeDataRecords stored in SSTable scylla metadata (tag 13). The transition is gated by a new LARGE_DATA_VIRTUAL_TABLES cluster feature flag: - Before the feature is enabled: the old physical tables remain in all_tables(), CQL writes are active, no virtual tables are registered. This ensures safe rollback during rolling upgrades. - After the feature is enabled: old physical tables are dropped from disk via legacy_drop_table_on_all_shards(), virtual tables are registered on all shards, and CQL writes are skipped via skip_cql_writes() in cql_table_large_data_handler. Key implementation details: - Three virtual table classes (large_partitions_virtual_table, large_rows_virtual_table, large_cells_virtual_table) extend streaming_virtual_table with cross-shard record collection. - generate_legacy_id() gains a version parameter; virtual tables use version 1 to get different UUIDs than the old physical tables. - compaction_time is derived from SSTable generation UUID at display time via UUID_gen::unix_timestamp(). - Legacy SSTables without LargeDataRecords emit synthetic summary rows based on above_threshold > 0 in LargeDataStats. - The activation logic uses two paths: when the feature is already enabled (test env, restart), it runs as a coroutine; when not yet enabled, it registers a when_enabled callback that runs inside seastar::async from feature_service::enable(). - sstable_3_x_test updated to use a simplified large_data_test_handler and validate LargeDataRecords in SSTable metadata directly.