Regression Tests
The regression tests are a comprehensive set of tests for the SQL
implementation in PostgreSQL. They test standard SQL operations as
well as the extended capabilities of PostgreSQL.
_________________________________________________________________
Running the Tests
The regression tests can be run against an already installed and
running server, or using a temporary installation within the build
tree. Furthermore, there is a "parallel" and a "sequential" mode for
running the tests. The sequential method runs each test script in
turn, whereas the parallel method starts up multiple server processes
to run groups of tests in parallel. Parallel testing gives confidence
that interprocess communication and locking are working correctly. For
historical reasons, the sequential test is usually run against an
existing installation and the parallel method against a temporary
installation, but there are no technical reasons for this.
To run the regression tests after building but before installation,
type
gmake check
in the top-level directory. (Or you can change to "src/test/regress"
and run the command there.) This will first build several auxiliary
files, such as some sample user-defined trigger functions, and then
run the test driver script. At the end you should see something like
======================
All 98 tests passed.
======================
or otherwise a note about which tests failed. See the section called
Test Evaluation below before assuming that a "failure" represents a
serious problem.
Because this test method runs a temporary server, it will not work
when you are the root user (since the server will not start as root).
If you already did the build as root, you do not have to start all
over. Instead, make the regression test directory writable by some
other user, log in as that user, and restart the tests. For example
root# chmod -R a+w src/test/regress
root# chmod -R a+w contrib/spi
root# su - joeuser
joeuser$ cd top-level build directory
joeuser$ gmake check
(The only possible "security risk" here is that other users might be
able to alter the regression test results behind your back. Use common
sense when managing user permissions.)
Alternatively, run the tests after installation.
If you have configured PostgreSQL to install into a location where an
older PostgreSQL installation already exists, and you perform gmake
check before installing the new version, you may find that the tests
fail because the new programs try to use the already-installed shared
libraries. (Typical symptoms are complaints about undefined symbols.)
If you wish to run the tests before overwriting the old installation,
you'll need to build with configure --disable-rpath. It is not
recommended that you use this option for the final installation,
however.
The parallel regression test starts quite a few processes under your
user ID. Presently, the maximum concurrency is twenty parallel test
scripts, which means sixty processes: there's a server process, a
psql, and usually a shell parent process for the psql for each test
script. So if your system enforces a per-user limit on the number of
processes, make sure this limit is at least seventy-five or so, else
you may get random-seeming failures in the parallel test. If you are
not in a position to raise the limit, you can cut down the degree of
parallelism by setting the MAX_CONNECTIONS parameter. For example,
gmake MAX_CONNECTIONS=10 check
runs no more than ten tests concurrently.
On some systems, the default Bourne-compatible shell ("/bin/sh") gets
confused when it has to manage too many child processes in parallel.
This may cause the parallel test run to lock up or fail. In such
cases, specify a different Bourne-compatible shell on the command
line, for example:
gmake SHELL=/bin/ksh check
If no non-broken shell is available, you may be able to work around
the problem by limiting the number of connections, as shown above.
To run the tests after installation, initialize a data area and start
the server, then type
gmake installcheck
or for a parallel test
gmake installcheck-parallel
The tests will expect to contact the server at the local host and the
default port number, unless directed otherwise by PGHOST and PGPORT
environment variables.
_________________________________________________________________
Test Evaluation
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 the section called Variant Comparison
Files for details.
_________________________________________________________________
Error message differences
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.
_________________________________________________________________
Locale differences
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.
_________________________________________________________________
Date and time differences
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.
_________________________________________________________________
Floating-point differences
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.
_________________________________________________________________
Row ordering differences
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.
_________________________________________________________________
The "random" test
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.
_________________________________________________________________
Variant Comparison Files
Since some of the tests inherently produce environment-dependent
results, we have provided ways to specify alternative "expected"
result files. Each regression test can have several comparison files
showing possible results on different platforms. There are two
independent mechanisms for determining which comparison file is used
for each test.
The first mechanism allows comparison files to be selected for
specific platforms. There is a mapping file,
"src/test/regress/resultmap", that defines which comparison file to
use for each platform. To eliminate bogus test "failures" for a
particular platform, you first choose or make a variant result file,
and then add a line to the "resultmap" file.
Each line in the mapping file is of the form
testname/platformpattern=comparisonfilename
The test name is just the name of the particular regression test
module. The platform pattern is a pattern in the style of the Unix
tool "expr" (that is, a regular expression with an implicit ^ anchor
at the start). It is matched against the platform name as printed by
"config.guess" followed by :gcc or :cc, depending on whether you use
the GNU compiler or the system's native compiler (on systems where
there is a difference). The comparison file name is the base name of
the substitute result comparison file.
For example: some systems interpret very small floating-point values
as zero, rather than reporting an underflow error. This causes a few
differences in the "float8" regression test. Therefore, we provide a
variant comparison file, "float8-small-is-zero.out", which includes
the results to be expected on these systems. To silence the bogus
"failure" message on OpenBSD platforms, "resultmap" includes
float8/i.86-.*-openbsd=float8-small-is-zero
which will trigger on any machine for which the output of
"config.guess" matches i.86-.*-openbsd. Other lines in "resultmap"
select the variant comparison file for other platforms where it's
appropriate.
The second selection mechanism for variant comparison files is much
more automatic: it simply uses the "best match" among several supplied
comparison files. The regression test driver script considers both the
standard comparison file for a test, testname.out, and variant files
named testname_digit.out (where the "digit" is any single digit 0-9).
If any such file is an exact match, the test is considered to pass;
otherwise, the one that generates the shortest diff is used to create
the failure report. (If "resultmap" includes an entry for the
particular test, then the base "testname" is the substitute name given
in "resultmap".)
For example, for the char test, the comparison file "char.out"
contains results that are expected in the C and POSIX locales, while
the file "char_1.out" contains results sorted as they appear in many
other locales.
The best-match mechanism was devised to cope with locale-dependent
results, but it can be used in any situation where the test results
cannot be predicted easily from the platform name alone. A limitation
of this mechanism is that the test driver cannot tell which variant is
actually "correct" for the current environment; it will just pick the
variant that seems to work best. Therefore it is safest to use this
mechanism only for variant results that you are willing to consider
equally valid in all contexts.
41cba49e95