https://clickhouse.com/docs/en/updating-data
https://clickhouse.com/docs/en/guides/developer/lightweight-delete#lightweight-delete-internals

https://github.com/ClickHouse/ClickHouse/tree/master/src

https://github.com/ClickHouse/ClickHouse/tree/master/src/Functions
https://github.com/ClickHouse/ClickHouse/blob/master/src/Functions/DateTimeTransforms.h
https://github.com/ClickHouse/ClickHouse/blob/master/src/Functions/IFunctionDateOrDateTime.h

https://github.com/ClickHouse/ClickHouse/tree/master/src/Storages

Clickhouse - Internal Structure of p19
https://www.youtube.com/playlist?list=PL0Z2YDlm0b3jsHXli7yll7CGHI9qyALmK

mutations
https://clickhouse.com/docs/en/sql-reference/statements/alter#mutations
    alter ... update|delete
    set mutations_sync 1

https://clickhouse.com/docs/en/optimize/skipping-indexes
    ! no secondary indices, because data is not stored in rows
    skip inexes (skp_idx_)
    ... alter table <> materialize index <> ... to apply newly added index

2024
https://altinity.com/blog/learning-to-appreciate-monotonic-functions-in-clickhouse
    https://github.com/ClickHouse/ClickHouse/blob/master/src/Functions/toYear.cpp
    https://github.com/ClickHouse/ClickHouse/blob/6dd675579f0df1004ea3ab55e6a9793d176af2a5/src/Functions/IFunctionDateOrDateTime.h#L47
2023
https://clickhouse.com/blog/handling-updates-and-deletes-in-clickhouse
https://habr.com/ru/companies/oleg-bunin/articles/726570/
    ! perf-opt

system db
\c system
\d

query_log