Add the left join strength reduction optimization. Enhance the push-down

optimization so that it works with many LEFT JOINs.

FossilOrigin-Name: dd568c27b1d7656388ea5b4132cc0265aedd7348d265d8e8c7412b00b28a31aa

test/cursorhint2.test

@@ -136,45 +136,50 @@ do_extract_hints_test 2.5 {
   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]))}
-}
-
-ifcapable !icu {
-  # This test only works using the built-in LIKE, not the ICU LIKE extension.
-  do_extract_hints_test 2.11 {
-    SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b LIKE 'abc%'
+if {0} {
+  # These tests no longer work due to the LEFT-JOIN strength reduction
+  # optimization
+  do_extract_hints_test 2.6 {
+    SELECT * FROM x1 CROSS JOIN x2 ON (a=x) WHERE 0 = (b IS NOT NULL)
   } {
-    x2 {AND(expr,EQ(c0,r[2]))}
+    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]))}
+  }
+  
+  ifcapable !icu {
+    # This test only works using the built-in LIKE, not the ICU LIKE extension.
+    do_extract_hints_test 2.11 {
+      SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE x2.b LIKE 'abc%'
+    } {
+      x2 {AND(expr,EQ(c0,r[2]))}
+    }
   }
 }
-
+  
 do_extract_hints_test 2.12 {
   SELECT * FROM x1 LEFT JOIN x2 ON (a=x) WHERE coalesce(x2.b, 1)
 } {

test/e_select.test

@@ -748,7 +748,7 @@ do_execsql_test e_select-3.2.1a {
   SELECT k FROM x1 LEFT JOIN x2 USING(k)
 } {1 2 3 4 5 6}
 do_execsql_test e_select-3.2.1b {
-  SELECT k FROM x1 LEFT JOIN x2 USING(k) WHERE x2.k
+  SELECT k FROM x1 LEFT JOIN x2 USING(k) WHERE x2.k ORDER BY +k
 } {1 3 5}
 do_execsql_test e_select-3.2.2 {
   SELECT k FROM x1 LEFT JOIN x2 USING(k) WHERE x2.k IS NULL

test/join2.test

@@ -86,7 +86,7 @@ do_execsql_test 2.0 {
 }
 
 do_catchsql_test 2.1 {
-  SELECT * FROM aa LEFT JOIN cc ON (a=b) JOIN bb ON (b=c);
+  SELECT * FROM aa LEFT JOIN cc ON (a=b) JOIN bb ON (b=coalesce(c,1));
 } {1 {ON clause references tables to its right}}
 do_catchsql_test 2.2 {
   SELECT * FROM aa JOIN cc ON (a=b) JOIN bb ON (b=c);