From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: parallel mode and parallel contexts |
Date: | 2015-01-07 13:11:12 |
Message-ID: | CA+TgmoYWbMmRX+1cr5HiwfMfndYD5WKcpK3wCQrJ4w_X=gjO1Q@mail.gmail.com |
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Lists: | pgsql-hackers |
On Tue, Jan 6, 2015 at 4:37 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> So when you say "Only the top frame of the transaction state stack is
> copied" you don't mean the top, you mean the bottom (the latest
> subxact)? Which then becomes the top in the parallel worker? OK...
The item most recently added to the stack is properly called the top,
but I guess it's confusing in this case because the item on the bottom
of the stack is referred to as the TopTransaction. I'll see if I can
rephrase that.
> Those comments really belong in a README, not the first visible
> comment in xact.c
OK.
> You need to start with the explanation that parallel workers have a
> faked-up xact stack to make it easier to copy and manage. That is
> valid because we never change xact state during a worker operation.
OK.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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