Some properly installed and fully functional
PostgreSQL installations can
“fail” some of these regression tests due to
platform-specific artifacts such as varying floating-point representation
and message wording. The tests are currently evaluated using a simple
diff
comparison against the outputs
generated on a reference system, so the results are sensitive to
small system differences. When a test is reported as
“failed”, always examine the differences between
expected and actual results; you may well find that the
differences are not significant. Nonetheless, we still strive to
maintain accurate reference files across all supported platforms,
so it can be expected that all tests pass.
The actual outputs of the regression tests are in files in the
src/test/regress/results
directory. The test
script uses diff
to compare each output
file against the reference outputs stored in the
src/test/regress/expected
directory. Any
differences are saved for your inspection in
src/test/regress/regression.diffs
. (Or you
can run diff
yourself, if you prefer.)
If for some reason a particular platform generates a “failure” for a given test, but inspection of the output convinces you that the result is valid, you can add a new comparison file to silence the failure report in future test runs. See Section 28.3, “Variant Comparison Files” for details.
Some of the regression tests involve intentional invalid input values. Error messages can come from either the PostgreSQL code or from the host platform system routines. In the latter case, the messages may vary between platforms, but should reflect similar information. These differences in messages will result in a “failed” regression test that can be validated by inspection.
If you run the tests against an already-installed server that was initialized with a collation-order locale other than C, then there may be differences due to sort order and follow-up failures. The regression test suite is set up to handle this problem by providing alternative result files that together are known to handle a large number of locales.
Most of the date and time results are dependent on the time zone
environment. The reference files are generated for time zone
PST8PDT
(Berkeley, California), and there will be
apparent failures if the tests are not run with that time zone setting.
The regression test driver sets environment variable
PGTZ
to PST8PDT
, which normally
ensures proper results.
Some of the tests involve computing 64-bit floating-point numbers (double
precision
) from table columns. Differences in
results involving mathematical functions of double
precision
columns have been observed. The float8
and
geometry
tests are particularly prone to small differences
across platforms, or even with different compiler optimization options.
Human eyeball comparison is needed to determine the real
significance of these differences which are usually 10 places to
the right of the decimal point.
Some systems display minus zero as -0
, while others
just show 0
.
Some systems signal errors from pow()
and
exp()
differently from the mechanism
expected by the current PostgreSQL
code.
You might see differences in which the same rows are output in a
different order than what appears in the expected file. In most cases
this is not, strictly speaking, a bug. Most of the regression test
scripts are not so pedantic as to use an ORDER BY
for every single
SELECT
, and so their result row orderings are not well-defined
according to the letter of the SQL specification. In practice, since we are
looking at the same queries being executed on the same data by the same
software, we usually get the same result ordering on all platforms, and
so the lack of ORDER BY
isn't a problem. Some queries do exhibit
cross-platform ordering differences, however. When testing against an
already-installed server, ordering differences can also be caused by
non-C locale settings or non-default parameter settings, such as custom values
of work_mem
or the planner cost parameters.
Therefore, if you see an ordering difference, it's not something to
worry about, unless the query does have an ORDER BY
that your
result is violating. But please report it anyway, so that we can add an
ORDER BY
to that particular query and thereby eliminate the bogus
“failure” in future releases.
You might wonder why we don't order all the regression test queries explicitly to get rid of this issue once and for all. The reason is that that would make the regression tests less useful, not more, since they'd tend to exercise query plan types that produce ordered results to the exclusion of those that don't.
If the errors
test results in a server crash
at the select infinite_recurse()
command, it means that
the platform's limit on process stack size is smaller than the
max_stack_depth
parameter indicates. This
can be fixed by running the server under a higher stack
size limit (4MB is recommended with the default value of
max_stack_depth
). If you are unable to do that, an
alternative is to reduce the value of max_stack_depth
.
The random
test script is intended to produce
random results. In rare cases, this causes the random regression
test to fail. Typing
diff results/random.out expected/random.out
should produce only one or a few lines of differences. You need not worry unless the random test fails repeatedly.