questions about PG update performance

Dear,

I have a question about update performance of PG.

Because of the internal implementation of MVCC in PG
the update of a row is actually a insertion of a new version row.
So if the size of a row is huge, then it incurs some overhead compare to
in-place update strategy.

Let's assume that a table has 200 columns,
and a user updates one of the columns of one row in the table.
Then PG will rewrite the whole contents of the updated row
including the updated columns and not-updated columns.

I'm not sure about the implementation of Oracle's update.
But if the Oracle can overwrite only the updated column,
the performance difference between Oracle and PG in that case may be
significant.

I researched about this issues in mailing list and google.
But I've not found anything related to this issues.

Thank you.

Kisung Kim.

(C)Bitnine, Kisung Kim, Ph.D
https://sites.google.com/site/kisungresearch/
E-mail : kskim(at)bitnine(dot)co(dot)kr
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