pgsql: In pgwin32_open, loop after ERROR_ACCESS_DENIED only if we can't - Mailing list pgsql-committers

From Tom Lane
Subject pgsql: In pgwin32_open, loop after ERROR_ACCESS_DENIED only if we can't
Date
Msg-id E1iinPg-0001av-J6@gemulon.postgresql.org
Whole thread Raw
List pgsql-committers
In pgwin32_open, loop after ERROR_ACCESS_DENIED only if we can't stat.

This fixes a performance problem introduced by commit 6d7547c21.
ERROR_ACCESS_DENIED is returned in some other cases besides the
delete-pending case considered by that commit; notably, if the
given path names a directory instead of a plain file.  In that
case we'll uselessly loop for 1 second before returning the
failure condition.  That slows down some usage scenarios enough
to cause test timeout failures on our Windows buildfarm critters.

To fix, try to stat() the file, and sleep/loop only if that fails.
It will fail in the delete-pending case, and also in the case where
the deletion completed before we could stat(), so we have the cases
where we want to loop covered.  In the directory case, the stat()
should succeed, letting us exit without a wait.

One case where we'll still wait uselessly is if the access-denied
problem pertains to a directory in the given pathname.  But we don't
expect that to happen in any performance-critical code path.

There might be room to refine this further, but I'll push it now
in hopes of making the buildfarm green again.

Back-patch, like the preceding commit.

Alexander Lakhin and Tom Lane

Discussion: https://postgr.es/m/23073.1576626626@sss.pgh.pa.us

Branch
------
REL_10_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/a69f5697ae13f92a3407647a5c419cccd541676a

Modified Files
--------------
src/port/open.c | 30 +++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)


pgsql-committers by date:

Previous
From: Bruce Momjian
Date:
Subject: pgsql: C comment: clarify why psql's help/exit/quit must alone
Next
From: Peter Eisentraut
Date:
Subject: pgsql: Fix compiler warning for ppoll() on Cygwin