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Merge issue about large data part with lightweight delete #56728
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@alexey-milovidov We plan to implement this feature. What are your thoughts on it? Do you think it's a good solution? |
Adding @alesapin as he also might have some thought about the topic. |
Yes, good idea - it will be appreciated. |
reverted #58097 |
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Use case
When a data part is larger than
max_bytes_to_merge_at_max_space_in_pool
, lightweight deleted data inside the data part will never be really deleted unlessOPTIMIZE FINAL
is executed.Describe the solution you'd like
When selecting parts to merge, use estimated existed rows size
(
bytes_on_disk * (rows_count - lwd_rows_count) / rows_count
) as the source part size instead ofbytes_on_disk
.We can enable this mode only when deleted rows ratio exceeds a certain value (maybe 25%).
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