On 23.12.21 12:40, Fabien COELHO wrote:
In [0], it was reported that certain replication commands result in
infinite loops because of faulty error handling. This still happens.
I wrote a test for it, attached here. (I threw in a few more basic
tests, just to have some more coverage that was lacking, and to have a
file to put the new test in.)
Hmmm… For some unclear reason on errors on a PGRES_COPY_* state
PQgetResult keeps on returning an empty result. PQexec manually ignores
it, so I did the same with a comment, but for me the real bug is somehow
in PQgetResult behavior…
In [1], it was reported that server crashes produce duplicate error
messages. This also still happens. I didn't write a test for it,
maybe you have an idea. (Obviously, we could check whether the error
message is literally there twice in the output, but that doesn't seem
very general.) But it's easy to test manually: just have psql
connect, shut down the server, then run a query.
This is also a feature/bug of libpq which happens to be hidden by
PQexec: when one command crashes PQgetResult actually returns *2*
results. First one with the FATAL message, second one when libpq figures
out that the connection was lost with the second message appended to the
first. PQexec just happen to silently ignore the first result. I added a
manual reset of the error message when first shown so that it is not
shown twice. It is unclear to me whether the reset should be somewhere
in libpq instead. I added a voluntary crash at the end of the psql test.
I agree that these two behaviors in libpq are dubious, especially the
second one. I want to spend some time analyzing this more and see if
fixes in libpq might be appropriate.
