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Doesn't seem to be much point in keeping this README up to date anymore,

Browse Source 
since it's completely redundant with regress.sgml.  I think we agreed to
remove it awhile back, actually, but no one got around to doing it.
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Tom Lane 2001-08-06 22:55:00 +00:00
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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. The test suite was
originally developed by Jolly Chen and Andrew Yu, and was extensively
revised and repackaged by Marc Fournier and Thomas Lockhart. From
PostgreSQL 6.1 onward the regression tests are current for every
official release.
The regression test 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 "stand-alone", but there
are 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 platform-dependent "expected" files and some sample
user-defined trigger functions, and then run the test driver
script. At the end you should see something like
======================
All 76 tests passed.
======================
or otherwise a note about what tests failed. See the section called
Test Evaluation below for more.
Note: Because this test method runs a temporary server, it will
not work when you are the root user (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# su - joeuser
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.
Tip: 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
To run the tests after installation, initialize a data area and start
the server, then type
$ gmake installcheck
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 time zone
support. 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.)
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 which can be validated by inspection.
Locale differences
The tests expect to run in plain "C" locale. This should not cause any
problems when you run the tests against a temporary installation, since
the regression test driver takes care to start the server in C locale.
However, if you run the tests against an already-installed server that
is using non-C locale settings, you may see differences caused by
varying rules for string sort order, formatting of numeric and monetary
values, and so forth.
In some locales the resulting differences are small and easily checked by
inspection. However, in a locale that changes the rules for formatting
of numeric values (typically by swapping the usage of commas and
decimal points), entry of some data values will fail, resulting in
extensive differences later in the tests where the missing data values
are supposed to be used.
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 to ensure proper
results. However, your system must provide library support for the
PST8PDT time zone, or the time zone-dependent tests will fail. To
verify that your machine does have this support, type the following:
$ env TZ=PST8PDT date
The command above should have returned the current system time in the
PST8PDT time zone. If the PST8PDT database is not available, then your
system may have returned the time in GMT. If the PST8PDT time zone is
not available, you can set the time zone rules explicitly:
PGTZ='PST8PDT7,M04.01.0,M10.05.03'; export PGTZ
There appear to be some systems which do not accept the recommended
syntax for explicitly setting the local time zone rules; you may need
to use a different PGTZ setting on such machines.
Some systems using older time zone libraries fail to apply
daylight-savings corrections to dates before 1970, causing pre-1970
PDT times to be displayed in PST instead. This will result in
localized differences in the test results.
Some of the queries in the "timestamp" test will fail if you run the
test on the day of a daylight-savings time changeover, or the day
before or after one. These queries assume that the intervals between
midnight yesterday, midnight today and midnight tomorrow are exactly
twenty-four hours -- which is wrong if daylight-savings time went into
or out of effect meanwhile.
Floating point differences
Some of the tests involve computing 64-bit (double precision) numbers
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 signal errors from pow() and exp() differently from the
mechanism expected by the current PostgreSQL code.
Polygon differences
Several of the tests involve operations on geographic data about the
Oakland/Berkeley, CA street map. The map data is expressed as polygons
whose vertices are represented as pairs of double precision numbers
(decimal latitude and longitude). Initially, some tables are created
and loaded with geographic data, then some views are created which
join two tables using the polygon intersection operator (##), then a
select is done on the view.
When comparing the results from different platforms, differences occur
in the 2nd or 3rd place to the right of the decimal point. The SQL
statements where these problems occur are the following:
SELECT * from street;
SELECT * from iexit;
Tuple ordering differences
You might see differences in which the same tuples 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 tuple orderings are not well-defined
according to the letter of the SQL spec. 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. (Ordering differences
can also be triggered by non-C locale settings.)
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 regress test SELECTs 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
There is at least one case in the "random" test script that is
intended to produce random results. This causes random to fail the
regression test once in a while (perhaps once in every five to ten
trials). 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 always fails in repeated attempts. (On
the other hand, if the random test is never reported to fail even in
many trials of the regress tests, you probably should worry.)
Platform-specific comparison files
Since some of the tests inherently produce platform-specific results,
we have provided a way to supply platform-specific result comparison
files. Frequently, the same variation applies to multiple platforms;
rather than supplying a separate comparison file for every platform,
there is a mapping file that defines which comparison file to use. So,
to eliminate bogus test "failures" for a particular platform, you must
choose or make a variant result file, and then add a line to the
mapping file, which is "resultmap".
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 expr(1)
(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 name of the substitute result comparison
file.
For example: the int2 regress test includes a deliberate entry of a
value that is too large to fit in int2. The specific error message
that is produced is platform-dependent; our reference platform emits
ERROR: pg_atoi: error reading "100000": Numerical result out of range
but a fair number of other Unix platforms emit
ERROR: pg_atoi: error reading "100000": Result too large
Therefore, we provide a variant comparison file, int2-too-large.out,
that includes this spelling of the error message. To silence the bogus
"failure" message on HPPA platforms, resultmap includes
int2/hppa=int2-too-large
which will trigger on any machine for which config.guess's output
begins with 'hppa'. Other lines in resultmap select the variant
comparison file for other platforms where it's appropriate.