Include WHERE terms in the cursor-hint passed to a cursor opened for the rhs of a LEFT JOIN iff we can be sure that those terms will not evaluate to true if the LEFT JOIN generates a row of NULLs.

FossilOrigin-Name: 998095aba01b75f685ed981b377e1dfe650d9bbf

test/cursorhint2.test

@@ -94,7 +94,74 @@ do_extract_hints_test 1.6 {
 do_extract_hints_test 1.7 {
   SELECT * FROM t1 LEFT JOIN t2 ON (a=c AND d=e) LEFT JOIN t3 ON (d=f);
 } {
-  t2 {EQ(r[2],c0)} t3 {EQ(r[6],c1)}
+  t2 {EQ(r[2],c0)} t3 {AND(EQ(r[6],c0),EQ(r[7],c1))}
+}
+
+#-------------------------------------------------------------------------
+#
+do_execsql_test 2.0 {
+  CREATE TABLE x1(x, y);
+  CREATE TABLE x2(a, b);
+}
+
+do_extract_hints_test 2.1 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE b IS NULL;
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.2 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE b IS +NULL;
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.3 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 1 = (b IS NULL)
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.4 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 1 = coalesce(b, 1)
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.5 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 1 = coalesce(b, 1)
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.6 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 0 = (b IS NOT NULL)
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.7 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE 0 = (b IS NOT +NULL)
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.8 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE b IS NOT +NULL
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.9 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE CASE b WHEN 0 THEN 0 ELSE 1 END;
+} {
+  x2 {EQ(c0,r[2])}
+}
+
+do_extract_hints_test 2.10 {
+  SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b = 32+32
+} {
+  x2 {AND(EQ(c1,ADD(32,32)),EQ(c0,r[2]))}
 }
 
 finish_test