Burst in WAL size when UUID is used as PK while full_page_writes are enabled

From: sanyam jain <sanyamjain22(at)live(dot)in>
To: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Burst in WAL size when UUID is used as PK while full_page_writes are enabled
Date: 2017-10-27 05:56:12
Message-ID: MAXPR01MB04921E5B05F67C25C2A895B8C05A0@MAXPR01MB0492.INDPRD01.PROD.OUTLOOK.COM
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Hi,

I was reading the blog https://blog.2ndquadrant.com/on-the-impact-of-full-page-writes .

My queries:

How randomness of UUID will likely to create new leaf page in btree index?
In my understanding as the size of UUID is 128 bits i.e. twice of BIGSERIAL , more number of pages will be required to store the same number of rows and hence there can be increase in WAL size due to FPW .
When compared the index size in local setup UUID index is ~2x greater in size.

Thanks,

Sanyam Jain

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