Date: Mon, 17 Jan 2022 19:15:40 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Langote <amitlangote09@gmail.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	Ibrar Ahmed <ibrar.ahmad@gmail.com>,
	Arne Roland <A.Roland@index.de>,
	"David G. Johnston" <david.g.johnston@gmail.com>,
	Masahiko Sawada <sawada.mshk@gmail.com>,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Rahila Syed <rahilasyed90@gmail.com>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>
Subject: Re: a misbehavior of partition row movement (?)
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On 2022-Jan-17, Tom Lane wrote:

> But could we please do it in a way that is designed to keep the
> code readable, rather than to minimize the number of lines of diff?
> It makes zero sense to have the bits in AFTER_TRIGGER_TUP_BITS not
> be adjacent.  So what should happen here is to renumber the symbols
> in between to move their bits over one place.

Is it typical to enumerate bits starting from the right of each byte,
when doing it from the high bits of the word?  DONE and IN_PROGRESS have
been defined as 0x1 and 0x2 of that byte for a very long time and I
found that very strange.  I am inclined to count from the left, so I'd
pick 8 first, defining the set like this:

#define AFTER_TRIGGER_OFFSET			0x07FFFFFF	/* must be low-order bits */
#define AFTER_TRIGGER_DONE			0x80000000
#define AFTER_TRIGGER_IN_PROGRESS		0x40000000
/* bits describing the size and tuple sources of this event */
#define AFTER_TRIGGER_FDW_REUSE			0x00000000
#define AFTER_TRIGGER_FDW_FETCH			0x20000000
#define AFTER_TRIGGER_1CTID			0x10000000
#define AFTER_TRIGGER_2CTID			0x30000000
#define AFTER_TRIGGER_CP_UPDATE			0x08000000
#define AFTER_TRIGGER_TUP_BITS			0x38000000

(The fact that FDW_REUSE bits is actually an empty mask comes from
7cbe57c34dec, specifically [1])

Is this what you were thinking?

[1] https://postgr.es/m/20140306033644.GA3527902@tornado.leadboat.com

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/
"All rings of power are equal,
But some rings of power are more equal than others."
                                 (George Orwell's The Lord of the Rings)