vinothchandar commented on code in PR #6612:
URL: https://github.com/apache/hudi/pull/6612#discussion_r1164843499


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+
+# RFC-58: A more effective HoodieMergeHandler for COW table with parquet
+
+## Proposers
+
+*   @loukey-lj
+
+## Approvers
+
+*   @<approver1 github username>
+
+*   @<approver2 github username>
+
+## Status
+
+JIRA: https://issues.apache.org/jira/browse/HUDI-4790
+
+> Please keep the status updated in `rfc/README.md`.
+
+## Abstract
+
+To provide a more effective HoodieMergeHandler for COW table with parquet. 
Hudi rewrite whole parquet file every COW, that costs a lot in De/serialization 
and De/compression.  To decrease this cost, a 'surgery' is introduced, which 
rebuilds a new parquet from an old one,  just copying unchanged rowGroups and 
overwriting changed rowGroups when updating parquet files.

Review Comment:
   Two questions:
   
   a) is there a way to copy over unchanged columns as well within each row 
group? or do this at the page level?  
   
   b) IIUC I think this helps in cases where the parquet file has multiple row 
groups and only few of them are changed? would you expect to see any 
performance improvements with the default 120 MB file size, with 120MB block 
size? i.e with just one row group in the parquet file



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