Adding upstream version 13.4.upstream/13.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/test/modules/test_predtest/README b/src/test/modules/test_predtest/README
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+test_predtest is a module for checking the correctness of the optimizer's
+predicate-proof logic, in src/backend/optimizer/util/predtest.c.
+
+The module provides a function that allows direct application of
+predtest.c's exposed functions, predicate_implied_by() and
+predicate_refuted_by(), to arbitrary boolean expressions, with direct
+inspection of the results.  This could be done indirectly by checking
+planner results, but it can be difficult to construct end-to-end test
+cases that prove that the expected results were obtained.
+
+In general, the use of this function is like
+	select * from test_predtest('query string')
+where the query string must be a SELECT returning two boolean
+columns, for example
+
+	select * from test_predtest($$
+	select x, not x
+	from (values (false), (true), (null)) as v(x)
+	$$);
+
+The function parses and plans the given query, and then applies the
+predtest.c code to the two boolean expressions in the SELECT list, to see
+if the first expression can be proven or refuted by the second.  It also
+executes the query, and checks the resulting rows to see whether any
+claimed implication or refutation relationship actually holds.  If the
+query is designed to exercise the expressions on a full set of possible
+input values, as in the example above, then this provides a mechanical
+cross-check as to whether the proof code has given a correct answer.