Re: WIP: WAL prefetch (another approach)

Thomas Munro escribió:

> @@ -1094,8 +1103,16 @@ WALRead(XLogReaderState *state,
> XLByteToSeg(recptr, nextSegNo, state->segcxt.ws_segsize);
> state->routine.segment_open(state, nextSegNo, &tli);
>
> - /* This shouldn't happen -- indicates a bug in segment_open */
> - Assert(state->seg.ws_file >= 0);
> + /* callback reported that there was no such file */
> + if (state->seg.ws_file < 0)
> + {
> + errinfo->wre_errno = errno;
> + errinfo->wre_req = 0;
> + errinfo->wre_read = 0;
> + errinfo->wre_off = startoff;
> + errinfo->wre_seg = state->seg;
> + return false;
> + }

Ah, this is what Michael was saying ... we need to fix WALRead so that
it doesn't depend on segment_open alway returning a good FD. This needs
a fix everywhere, not just here, and improve the error report interface.

Maybe it does make sense to get it fixed in pg13 and avoid a break
later.

--
Álvaro Herrera https://www.2ndQuadrant.com/
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