RE: Parallel heap vacuum

Dear Sawda-san,

> 
> I've attached new version patches that fixes failures reported by
> cfbot. I hope these changes make cfbot happy.

Thanks for updating the patch and sorry for delaying the reply. I confirmed cfbot
for Linux/Windows said ok.
I'm still learning the feature so I can post only one comment :-(.

I wanted to know whether TidStoreBeginIterateShared() was needed. IIUC, pre-existing API,
TidStoreBeginIterate(), has already accepted the shared TidStore. The only difference
is whether elog(ERROR) exists, but I wonder if it benefits others. Is there another
reason that lazy_vacuum_heap_rel() uses TidStoreBeginIterateShared()?

Another approach is to restrict TidStoreBeginIterate() to support only the local one.
How do you think?

Best regards,
Hayato Kuroda
FUJITSU LIMITED