Re: standby recovery fails (tablespace related) (tentative patch and discussion)

Here's a couple of fixups. 0001 is the same as before. In 0002 I think
CheckTablespaceDirectory ends up easier to read if we split out the test
for validity of the link. Looking at that again, I think we don't need
to piggyback on ignore_invalid_pages, which is already a stretch, so
let's not -- instead we can use allow_in_place_tablespaces if users need
a workaround. So that's 0003 (this bit needs more than zero docs,
however.)

0004 is straightforward: let's check for bad directories before logging
about consistent state.

After all this, I'm not sure what to think of dbase_redo. At line 3102,
is the directory supposed to exist or not? I'm confused as to what is
the expected state at that point. I rewrote this, but now I think my
rewrite continues to be confusing, so I'll have to think more about it.

Another aspect are the tests. Robert described a scenario where the
previously committed version of this patch created trouble. Do we have
a test case to cover that problematic case? I think we should strive to
cover it, if possible.

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"The eagle never lost so much time, as
when he submitted to learn of the crow." (William Blake)