Re: [HACKERS] Setting pd_lower in GIN metapage

On Sun, Sep 24, 2017 at 2:25 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> Added and updated the comments for both btree and hash index patches.

I don't have real complaints about this patch, this looks fine to me.

+    * Currently, the advantage of setting pd_lower is in limited cases like
+    * during wal_consistency_checking or while logging for unlogged relation
+    * as for all other purposes, we initialize the metapage.  Note, it also
+    * helps in page masking by allowing to mask unused space.
I would have reworked this comment a bit, say like that:
Setting pd_lower is useful for two cases which make use of WAL
compressibility even if the meta page is initialized at replay:
- Logging of init forks for unlogged relations.
- wal_consistency_checking logs extra full-page writes, and this
allows masking of the unused space of the page.

Now I often get complains that I suck at this exercise ;)
-- 
Michael


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