Re: read() returns ERANGE in Mac OS X

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> We just came across a situation where a corrupted HFS+ filesystem
> appears to return ERANGE on a customer machine.  Our first reaction was
> to turn zero_damaged_pages on to allow taking a pg_dump backup of the
> database, but surprisingly this does not work.  A quick glance at the
> code shows the reason:
> ...
> Note that zero_damaged_pages only enters the picture if it's a short
> read, not if the read actually fails completely.

> Is this by design, or is this just an oversight?

It is by design, in that the only contemplated case was truncated-away
pages.  I'm pretty hesitant to consider allowing arbitrary kernel errors
to be ignored here ...
        regards, tom lane