From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Heikki Linnakangas <hlinnaka@iki.fi>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: BRIN page type identifier
In-reply-to: <8620.1425944081@sss.pgh.pa.us>
References: <546A16EF.9070005@vmware.com>
 <20150309223505.GT3291@alvh.no-ip.org> <8620.1425944081@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
 message dated "Mon, 09 Mar 2015 19:34:41 -0400"
Date: Mon, 09 Mar 2015 23:39:11 -0400
Message-ID: <14066.1425958751@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

I wrote:
> You could try something like
> typedef struct BrinSpecialSpace
> {
> 	uint16		vector[MAXALIGN(1) / sizeof(uint16)];
> } BrinSpecialSpace;
> and then some access macros to use the last and next-to-last
> elements of that array.

On second thought, consider

typedef struct BrinSpecialSpace
{
	uint16		flags;
	uint16		vector[MAXALIGN(1) / sizeof(uint16) - 1];
} BrinSpecialSpace;

This way, accesses to "flags" require no source code changes.
You still need a macro to map "type" onto the last element of
the vector, but there's probably about one reference to "type"
in the source code so it shouldn't be too painful.

			regards, tom lane


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