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Bug fix in the LEFT JOIN strength reduction optimization of

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check-in [dd568c27b1d76563].  The sqlite3ExprImpliesNotNull() routine was
mistakenly assuming that a CASE expression must always be NULL if contained
any reference to a variable that was NULL.

FossilOrigin-Name: cf171abe954a5f25262161dd69f2e8cecdbf9446c3f6b298201507dbc743567e
This commit is contained in:
drh
2018-03-24 13:24:02 +00:00
parent b873f4e404
commit 2c492061ce
4 changed files with 58 additions and 8 deletions
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49
test/join.test
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@ -780,4 +780,53 @@ do_execsql_test join-14.20 {
LEFT JOIN t3 AS x3 ON x2.id=x3.c3;
} {456 {} {}}
# 2018-03-24.
# E.Pasma discovered that the LEFT JOIN strength reduction optimization
# was misbehaving. The problem turned out to be that the
# sqlite3ExprImpliesNotNull() routine was saying that CASE expressions
# like
#
# CASE WHEN true THEN true ELSE x=0 END
#
# could never be true if x is NULL. The following test cases verify
# that this error has been resolved.
#
db close
sqlite3 db :memory:
do_execsql_test join-15.100 {
CREATE TABLE t1(a INT, b INT);
INSERT INTO t1 VALUES(1,2),(3,4);
CREATE TABLE t2(x INT, y INT);
SELECT *, 'x'
FROM t1 LEFT JOIN t2
WHERE CASE WHEN FALSE THEN a=x ELSE 1 END;
} {1 2 {} {} x 3 4 {} {} x}
do_execsql_test join-15.110 {
DROP TABLE t1;
DROP TABLE t2;
CREATE TABLE t1(a INTEGER PRIMARY KEY, b INTEGER);
INSERT INTO t1(a,b) VALUES(1,0),(11,1),(12,1),(13,1),(121,12);
CREATE INDEX t1b ON t1(b);
CREATE TABLE t2(x INTEGER PRIMARY KEY);
INSERT INTO t2(x) VALUES(0),(1);
SELECT a1, a2, a3, a4, a5
FROM (SELECT a AS a1 FROM t1 WHERE b=0)
JOIN (SELECT x AS x1 FROM t2)
LEFT JOIN (SELECT a AS a2, b AS b2 FROM t1)
ON x1 IS TRUE AND b2=a1
JOIN (SELECT x AS x2 FROM t2)
ON x2<=CASE WHEN x1 THEN CASE WHEN a2 THEN 1 ELSE -1 END ELSE 0 END
LEFT JOIN (SELECT a AS a3, b AS b3 FROM t1)
ON x2 IS TRUE AND b3=a2
JOIN (SELECT x AS x3 FROM t2)
ON x3<=CASE WHEN x2 THEN CASE WHEN a3 THEN 1 ELSE -1 END ELSE 0 END
LEFT JOIN (SELECT a AS a4, b AS b4 FROM t1)
ON x3 IS TRUE AND b4=a3
JOIN (SELECT x AS x4 FROM t2)
ON x4<=CASE WHEN x3 THEN CASE WHEN a4 THEN 1 ELSE -1 END ELSE 0 END
LEFT JOIN (SELECT a AS a5, b AS b5 FROM t1)
ON x4 IS TRUE AND b5=a4
ORDER BY a1, a2, a3, a4, a5;
} {1 {} {} {} {} 1 11 {} {} {} 1 12 {} {} {} 1 12 121 {} {} 1 13 {} {} {}}
finish_test