
                              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 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.
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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.
     _________________________________________________________________

                         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.
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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" 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.
