[GitHub] [iceberg] kbendick commented on a diff in pull request #3432: Doc: add a page to explain row-level deletes

[GitBox <gi...@apache.org>]

kbendick commented on code in PR #3432:
URL: https://github.com/apache/iceberg/pull/3432#discussion_r857882769


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site/docs/row-level-deletes.md:
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+
+# Row-Level Deletes
+
+Iceberg supports metadata-based deletion through the `DeleteFiles` interface.
+It allows you to quickly delete a specific file or any file that might match a given expression without the need to read or write any data in the table.
+
+Row-level deletes target more complicated use cases such as general data protection regulation (GDPR).
+Copy-on-write and merge-on-read are two different approaches to handle row-level delete operations. Here are their definitions in Iceberg:
+
+- **copy-on-write**: a delete directly rewrites all the affected data files.
+- **merge-on-read**: delete information is encoded in the form of _delete files_. The table reader can apply all delete information at read time.
+
+Overall, copy-on-write is more efficient in reading data, whereas merge-on-read is more efficient in writing deletes, but requires more maintenance and tuning to be performant in reading data with deletes.
+Users can choose to use **both** copy-on-write and merge-on-read for the same Iceberg table based on different situations. 
+For example, a time-partitioned table can have newer partitions maintained with the merge-on-read approach through a streaming pipeline,
+and older partitions maintained with the copy-on-write approach to apply less frequent GDPR deletes from batch ETL jobs.
+
+There are use cases that could only be supported by one approach such as change data capture (CDC).

Review Comment:
   +1. Since this is the primary explainer we should be careful in how absolute of terms we explain things as many people might not read more than just this.



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