
                              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.
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                              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 100 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 forty processes: there's a server process and a
   psql process 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 fifty 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.

   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.

   The source distribution also contains regression tests for the optional
   procedural languages and for some of the "contrib" modules. At present,
   these tests can be used only against an already-installed server. To
   run the tests for all procedural languages that have been built and
   installed, change to the "src/pl" directory of the build tree and type
gmake installcheck

   You can also do this in any of the subdirectories of "src/pl" to run
   tests for just one procedural language. To run the tests for all
   "contrib" modules that have them, change to the "contrib" directory of
   the build tree and type
gmake installcheck

   The "contrib" modules must have been built and installed first. You can
   also do this in a subdirectory of "contrib" to run the tests for just
   one module.
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                               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.
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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.
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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.
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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.
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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.
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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.
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Insufficient stack depth

   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.
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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". 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.
