Rewrite DELETE docs

[justindeguzman]

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[thomoco]

Very nice set of changes, thank you

I was wondering - should we perhaps be recommending wide parts in all use cases where many deletions are expected?

[evillique]

We should also compare it to the ALTER TABLE ... DELETE in ways that ALTER DELETE will actually delete the data, but it will recreate all the affected parts, which may take a lot of resources at the moment of deletion. At the same time, the DELETE query will not load ClickHouse as much because we only mark the rows as deleted, but it may take a lot of time for the data to be actually deleted.

[justindeguzman]

@evillique Thank you for reviewing. I believe I've addressed all of your feedback above in the most recent commit.

Please let me know if there are any more changes I should make.

[den-crane]

Very nice set of changes, thank you

I was wondering - should we perhaps be recommending wide parts in all use cases where many deletions are expected?

May be it has sense to put _row_exists into a separate file always, even if a part is compact. Compact parts are introduced to solve the overhead of small inserts, but delete happens when inserts already done (no overhead) and this column does not exists in the data.bin (no need to update data in the data.bin).

[evillique]

Looks perfect, thank you!

[nellicus]

thank you @evillique @justindeguzman ! 🙏