Re: Way to check whether a particular block is on the shared_buffer?

Kouhei Kaigai wrote:
> > On 1/31/16 7:38 PM, Kouhei Kaigai wrote:

> > To answer your direct question, I'm no expert, but I haven't seen any
> > functions that do exactly what you want. You'd have to pull relevant
> > bits from ReadBuffer_*. Or maybe a better method would just be to call
> > BufTableLookup() without any locks and if you get a result > -1 just
> > call the relevant ReadBuffer function. Sometimes you'll end up calling
> > ReadBuffer even though the buffer isn't in shared buffers, but I would
> > think that would be a rare occurrence.
> >
> Thanks, indeed, extension can call BufTableLookup(). PrefetchBuffer()
> has a good example for this.
> 
> If it returned a valid buf_id, we have nothing difficult; just call
> ReadBuffer() to pin the buffer.

Isn't this what (or very similar to)
ReadBufferExtended(RBM_ZERO_AND_LOCK) is already doing?

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services