Re: [HACKERS] large object regression tests

On Thu, 21 Sep 2006, Tom Lane wrote:

> Jeremy Drake <pgsql-patches(at)jdrake(dot)com> writes:
> > I put together a patch which adds a regression test for large objects,
> > hopefully attached to this message. I would like some critique of it, to
> > see if I have gone about it the right way. Also I would be happy to hear
> > any additional tests which should be added to it.
>
> I'd prefer it if we could arrange not to need any absolute paths
> embedded into the test, because maintaining tests that require such is
> a real PITA --- instead of just committing the actual test output, one
> has to reverse-convert it to a ".source" file.

I just copied how the test for COPY worked, since I perceived a similarity
in what I needed to do (use external files to load data).

> I suggest that instead of testing the server-side lo_import/lo_export
> functions, perhaps you could test the psql equivalents and write and
> read a file in psql's working directory.

I did not see any precedent for that when I was looking around in the
existing tests for an example of how to do things. I am not even sure
where the cwd of psql is, so I can put an input file there. Could you
provide an example of how this might look, by telling me where to put a
file in the src/test/regress tree and the path to give to \lo_import?
Besides which, shouldn't both the server-side and psql versions be tested?
When I was looking at the copy tests, it looked like the server-side ones
were tested, and then the psql ones were tested by exporting and then
importing data which was originally loaded from the server-side method.
Am I correctly interpreting the precedent, or are you suggesting that the
precedent be changed? I was trying to stay as close to the copy tests as
possible since the functionality is so similar (transferring data to/from
files in the filesystem, either via server-side functions which require
absolute paths or via psql \ commands (which I forgot about for the lo
funcs)).

> I think we could do without the Moby Dick extract too ...

I am open to suggestions. I saw one suggestion that I use an image of an
elephant, but I suspect that was tongue-in-cheek. I am not very fond of
the idea of generating repetitious data, as I think it would be more
difficult to determine whether or not the loseek/tell functions put me in
the right place in the middle of the file. Perhaps if there was a way to
generate deterministic pseudo-random data, that would work (has to be
deterministic so the diffs of the output come out right). Anyone have a
good example of seeding a random number generator and generating a bunch
of bytea which is deterministic cross-platform?

>
> regards, tom lane
>

In the mean time, I will alter the test to also test the psql backslash
commands based on how the copy equivalents are tested, since I had
forgotten them and they need to be tested also.

--
Any sufficiently advanced technology is indistinguishable from a rigged
demo.