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Teach optimizer's predtest.c more things about ScalarArrayOpExpr.

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In particular, make it possible to prove/refute "x IS NULL" and
"x IS NOT NULL" predicates from a clause involving a ScalarArrayOpExpr
even when we are unable or unwilling to deconstruct the expression
into an AND/OR tree.  This avoids a former unexpected degradation of
plan quality when the size of an ARRAY[] expression or array constant
exceeded the arbitrary MAX_SAOP_ARRAY_SIZE limit.  For IS-NULL proofs,
we don't really care about the values of the individual array elements;
at most, we care whether there are any, and for some common cases we
needn't even know that.

The main user-visible effect of this is to let the optimizer recognize
applicability of partial indexes with "x IS NOT NULL" predicates to
queries with "x IN (array)" clauses in some cases where it previously
failed to recognize that.  The structure of predtest.c is such that a
bunch of related proofs will now also succeed, but they're probably
much less useful in the wild.

James Coleman, reviewed by David Rowley

Discussion: https://postgr.es/m/CAAaqYe8yKSvzbyu8w-dThRs9aTFMwrFxn_BkTYeXgjqe3CbNjg@mail.gmail.com
This commit is contained in:
Tom Lane
2019-03-01 17:14:07 -05:00
parent aad21d4c3c
commit 65ce07e020
3 changed files with 478 additions and 20 deletions
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257
src/test/modules/test_predtest/expected/test_predtest.out
View File

@ -19,6 +19,9 @@ from generate_series(0, 11*11-1) i;
-- and a simple strict function that's opaque to the optimizer
create function strictf(bool, bool) returns bool
language plpgsql as $$begin return $1 and not $2; end$$ strict;
-- a simple function to make arrays opaque to the optimizer
create function opaque_array(int[]) returns int[]
language plpgsql as $$begin return $1; end$$ strict;
-- Basic proof rules for single boolean variables
select * from test_predtest($$
select x, x
@ -837,3 +840,257 @@ w_i_holds | f
s_r_holds | f
w_r_holds | f
-- In these tests, we want to prevent predtest.c from breaking down the
-- ScalarArrayOpExpr into an AND/OR tree, so as to exercise the logic
-- that handles ScalarArrayOpExpr directly. We use opaque_array() if
-- possible, otherwise an array longer than MAX_SAOP_ARRAY_SIZE.
-- ScalarArrayOpExpr implies scalar IS NOT NULL
select * from test_predtest($$
select x is not null, x = any(opaque_array(array[1]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | t
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | t
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- but for ALL, we have to be able to prove the array nonempty
select * from test_predtest($$
select x is not null, x <> all(opaque_array(array[1]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | t
w_i_holds | f
s_r_holds | f
w_r_holds | f
select * from test_predtest($$
select x is not null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101
])
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | t
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | t
w_i_holds | f
s_r_holds | f
w_r_holds | f
select * from test_predtest($$
select x is not null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,y
])
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | t
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | t
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- check empty-array cases
select * from test_predtest($$
select x is not null, x = any(opaque_array(array[]::int[]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | t
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | t
w_i_holds | t
s_r_holds | t
w_r_holds | t
select * from test_predtest($$
select x is not null, x <> all(opaque_array(array[]::int[]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- same thing under a strict function doesn't prove it
select * from test_predtest($$
select x is not null, strictf(true, x = any(opaque_array(array[]::int[])))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- ScalarArrayOpExpr refutes scalar IS NULL
select * from test_predtest($$
select x is null, x = any(opaque_array(array[1]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | t
weak_refuted_by | t
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | t
-- but for ALL, we have to be able to prove the array nonempty
select * from test_predtest($$
select x is null, x <> all(opaque_array(array[1]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | t
select * from test_predtest($$
select x is null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101
])
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | t
weak_refuted_by | t
s_i_holds | f
w_i_holds | f
s_r_holds | t
w_r_holds | t
-- check empty-array cases
select * from test_predtest($$
select x is null, x = any(opaque_array(array[]::int[]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | t
weak_refuted_by | t
s_i_holds | t
w_i_holds | t
s_r_holds | t
w_r_holds | t
select * from test_predtest($$
select x is null, x <> all(opaque_array(array[]::int[]))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- same thing under a strict function doesn't prove it
select * from test_predtest($$
select x is null, strictf(true, x = any(opaque_array(array[]::int[])))
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | f
s_r_holds | f
w_r_holds | f
-- Also, nullness of the scalar weakly refutes a SAOP
select * from test_predtest($$
select x = any(opaque_array(array[1])), x is null
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | t
s_i_holds | f
w_i_holds | t
s_r_holds | f
w_r_holds | t
-- as does nullness of the array
select * from test_predtest($$
select x = any(opaque_array(array[y])), array[y] is null
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | t
s_i_holds | t
w_i_holds | t
s_r_holds | t
w_r_holds | t
-- ... unless we need to prove array empty
select * from test_predtest($$
select x = all(opaque_array(array[1])), x is null
from integers
$$);
-[ RECORD 1 ]-----+--
strong_implied_by | f
weak_implied_by | f
strong_refuted_by | f
weak_refuted_by | f
s_i_holds | f
w_i_holds | t
s_r_holds | f
w_r_holds | t

115
src/test/modules/test_predtest/sql/test_predtest.sql
View File

@ -25,6 +25,10 @@ from generate_series(0, 11*11-1) i;
create function strictf(bool, bool) returns bool
language plpgsql as $$begin return $1 and not $2; end$$ strict;
-- a simple function to make arrays opaque to the optimizer
create function opaque_array(int[]) returns int[]
language plpgsql as $$begin return $1; end$$ strict;
-- Basic proof rules for single boolean variables
select * from test_predtest($$
@ -325,3 +329,114 @@ select * from test_predtest($$
select x <= y, x = any(array[1,3,y])
from integers
$$);
-- In these tests, we want to prevent predtest.c from breaking down the
-- ScalarArrayOpExpr into an AND/OR tree, so as to exercise the logic
-- that handles ScalarArrayOpExpr directly. We use opaque_array() if
-- possible, otherwise an array longer than MAX_SAOP_ARRAY_SIZE.
-- ScalarArrayOpExpr implies scalar IS NOT NULL
select * from test_predtest($$
select x is not null, x = any(opaque_array(array[1]))
from integers
$$);
-- but for ALL, we have to be able to prove the array nonempty
select * from test_predtest($$
select x is not null, x <> all(opaque_array(array[1]))
from integers
$$);
select * from test_predtest($$
select x is not null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101
])
from integers
$$);
select * from test_predtest($$
select x is not null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,y
])
from integers
$$);
-- check empty-array cases
select * from test_predtest($$
select x is not null, x = any(opaque_array(array[]::int[]))
from integers
$$);
select * from test_predtest($$
select x is not null, x <> all(opaque_array(array[]::int[]))
from integers
$$);
-- same thing under a strict function doesn't prove it
select * from test_predtest($$
select x is not null, strictf(true, x = any(opaque_array(array[]::int[])))
from integers
$$);
-- ScalarArrayOpExpr refutes scalar IS NULL
select * from test_predtest($$
select x is null, x = any(opaque_array(array[1]))
from integers
$$);
-- but for ALL, we have to be able to prove the array nonempty
select * from test_predtest($$
select x is null, x <> all(opaque_array(array[1]))
from integers
$$);
select * from test_predtest($$
select x is null, x <> all(array[
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,
29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,
79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101
])
from integers
$$);
-- check empty-array cases
select * from test_predtest($$
select x is null, x = any(opaque_array(array[]::int[]))
from integers
$$);
select * from test_predtest($$
select x is null, x <> all(opaque_array(array[]::int[]))
from integers
$$);
-- same thing under a strict function doesn't prove it
select * from test_predtest($$
select x is null, strictf(true, x = any(opaque_array(array[]::int[])))
from integers
$$);
-- Also, nullness of the scalar weakly refutes a SAOP
select * from test_predtest($$
select x = any(opaque_array(array[1])), x is null
from integers
$$);
-- as does nullness of the array
select * from test_predtest($$
select x = any(opaque_array(array[y])), array[y] is null
from integers
$$);
-- ... unless we need to prove array empty
select * from test_predtest($$
select x = all(opaque_array(array[1])), x is null
from integers
$$);