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Fix test_predtest's idea of what weak refutation means.

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I'd initially supposed that predicate_refuted_by(..., true) ought to
say that "A refutes B" means "non-falsity of A implies non-truth of B".
But it seems better to define it as "truth of A implies non-truth of B".
This is more useful in the current system, slightly easier to prove,
and in closer correspondence to the existing code behavior.

With this change, test_predtest no longer claims that any existing
test cases show false proof reports, though there still are cases
where we could prove something and fail to.

Discussion: https://postgr.es/m/5983.1520487191@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2018-03-08 19:44:14 -05:00
parent 960df2a971
commit a63c3274a6
2 changed files with 11 additions and 9 deletions
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12
src/test/modules/test_predtest/expected/test_predtest.out
View File

@ -119,7 +119,6 @@ select * from test_predtest($$
select x is not true, x
from booleans
$$);
WARNING: weak_refuted_by result is incorrect
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
@ -128,7 +127,7 @@ weak_refuted_by | t
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | f
w_r_holds | t
select * from test_predtest($$
select x, x is not true
@ -176,7 +175,6 @@ select * from test_predtest($$
select x is unknown, x
from booleans
$$);
WARNING: weak_refuted_by result is incorrect
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
@ -185,7 +183,7 @@ weak_refuted_by | t
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | f
w_r_holds | t
select * from test_predtest($$
select x, x is unknown
@ -214,7 +212,7 @@ weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | f
w_r_holds | t
select * from test_predtest($$
select x, x is null
@ -650,7 +648,7 @@ weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | f
w_r_holds | t
select * from test_predtest($$
select x is null, int4lt(x,8)
@ -664,7 +662,7 @@ weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | f
w_r_holds | t
select * from test_predtest($$
select x is not null, x < 'foo'

8
src/test/modules/test_predtest/test_predtest.c
View File

@ -104,14 +104,18 @@ test_predtest(PG_FUNCTION_ARGS)
c2 = 'f';
/* Check for violations of various proof conditions */
/* strong implication: truth of c2 implies truth of c1 */
if (c2 == 't' && c1 != 't')
s_i_holds = false;
/* weak implication: non-falsity of c2 implies non-falsity of c1 */
if (c2 != 'f' && c1 == 'f')
w_i_holds = false;
/* strong refutation: truth of c2 implies falsity of c1 */
if (c2 == 't' && c1 != 'f')
s_r_holds = false;
/* XXX is this the correct definition for weak refutation? */
if (c2 != 'f' && c1 == 't')
/* weak refutation: truth of c2 implies non-truth of c1 */
if (c2 == 't' && c1 == 't')
w_r_holds = false;
}