Re: Does TupleQueueReaderNext() really need to copy its result?

On Fri, Aug 23, 2019 at 10:22 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> Couldn't resist trying this, and it seems to work.  Based on the
> comment "the buffer size is a multiple of MAXIMUM_ALIGNOF, and each
> read and write is as well", it should always work (though I wish
> shm_mq_receive_bytes()'s documentation would discuss message alignment
> explicitly if that's true).  On the other hand, I doubt it makes a
> difference, so this is more of a question: is this the way it was
> supposed to work?

There's a comment in htup.h which says:

 * * Separately allocated tuple: t_data points to a palloc'd chunk that
 *       is not adjacent to the HeapTupleData.  (This case is deprecated since
 *       it's difficult to tell apart from case #1.  It should be used only in
 *       limited contexts where the code knows that case #1 will never apply.)

I got scared and ran away.

-- 
Robert Haas
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