Fix faulty asserts in the code generator.

Ticket [c52b09c7f38903b1]

src/select.c

@@ -5869,8 +5869,15 @@ int sqlite3Select(
     ** technically harmless for it to be generated multiple times. The
     ** following assert() will detect if something changes to cause
     ** the same subquery to be coded multiple times, as a signal to the
-    ** developers to try to optimize the situation. */
-    assert( pItem->addrFillSub==0 );
+    ** developers to try to optimize the situation.
+    **
+    ** Update 2019-07-24:
+    ** See ticket https://sqlite.org/src/tktview/c52b09c7f38903b1311cec40.
+    ** The dbsqlfuzz fuzzer found a case where the same subquery gets
+    ** coded twice.  So this assert() now becomes a testcase().  It should
+    ** be very rare, though.
+    */
+    testcase( pItem->addrFillSub!=0 );
 
     /* Increment Parse.nHeight by the height of the largest expression
     ** tree referred to by this, the parent select. The child select
@@ -5944,7 +5951,7 @@ int sqlite3Select(
       int retAddr;
       struct SrcList_item *pPrior;
 
-      assert( pItem->addrFillSub==0 );
+      testcase( pItem->addrFillSub==0 ); /* Ticket c52b09c7f38903b1311 */
       pItem->regReturn = ++pParse->nMem;
       topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
       pItem->addrFillSub = topAddr+1;

test/select1.test

@@ -1100,4 +1100,69 @@ do_execsql_test select1-17.3 {
          UNION ALL SELECT * FROM t2 WHERE y=3 ORDER BY y,z LIMIT 4);
 } {1 2 3}
 
+# 2019-07-24 Ticket https://sqlite.org/src/tktview/c52b09c7f38903b1311
+#
+do_execsql_test select1-18.1 {
+  DROP TABLE IF EXISTS t1;
+  DROP TABLE IF EXISTS t2;
+  CREATE TABLE t1(c);
+  CREATE TABLE t2(x PRIMARY KEY, y);
+  INSERT INTO t1(c) VALUES(123);
+  INSERT INTO t2(x) VALUES(123);
+  SELECT x FROM t2, t1 WHERE x BETWEEN c AND null OR x AND
+  x IN ((SELECT x FROM (SELECT x FROM t2, t1 
+  WHERE x BETWEEN (SELECT x FROM (SELECT x COLLATE rtrim 
+  FROM t2, t1 WHERE x BETWEEN c AND null
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND null
+  OR x AND x IN (c)) AND null
+  OR NOT EXISTS(SELECT -4.81 FROM t1, t2 WHERE x BETWEEN c AND null
+  OR x AND x IN ((SELECT x FROM (SELECT x FROM t2, t1
+  WHERE x BETWEEN (SELECT x FROM (SELECT x BETWEEN c AND null
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND null
+  OR x AND x IN (c)) AND null
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND null
+  OR x AND x IN (c)))) AND x IN (c)
+  ), t1 WHERE x BETWEEN c AND null
+  OR x AND x IN (c)));
+} {}
+do_execsql_test select1-18.2 {
+  DROP TABLE IF EXISTS t1;
+  DROP TABLE IF EXISTS t2;
+  CREATE TABLE t1(c);
+  CREATE TABLE t2(x PRIMARY KEY, y);
+  INSERT INTO t1(c) VALUES(123);
+  INSERT INTO t2(x) VALUES(123);
+  SELECT x FROM t2, t1 WHERE x BETWEEN c AND (c+1) OR x AND
+  x IN ((SELECT x FROM (SELECT x FROM t2, t1 
+  WHERE x BETWEEN (SELECT x FROM (SELECT x COLLATE rtrim 
+  FROM t2, t1 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN (c)) AND (c+1)
+  OR NOT EXISTS(SELECT -4.81 FROM t1, t2 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN ((SELECT x FROM (SELECT x FROM t2, t1
+  WHERE x BETWEEN (SELECT x FROM (SELECT x BETWEEN c AND (c+1)
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN (c)) AND (c+1)
+  OR x AND x IN (c)), t1 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN (c)))) AND x IN (c)
+  ), t1 WHERE x BETWEEN c AND (c+1)
+  OR x AND x IN (c)));
+} {123}
+do_execsql_test select1-18.3 {
+  SELECT 1 FROM t1 WHERE (
+    SELECT 2 FROM t2 WHERE (
+      SELECT 3 FROM (
+        SELECT x FROM t2 WHERE x=c OR x=(SELECT x FROM (VALUES(0)))
+      ) WHERE x>c OR x=c
+    )
+  );
+} {1}
+do_execsql_test select1-18.4 {
+  SELECT 1 FROM t1, t2 WHERE (
+    SELECT 3 FROM (
+      SELECT x FROM t2 WHERE x=c OR x=(SELECT x FROM (VALUES(0)))
+    ) WHERE x>c OR x=c
+  );
+} {1}
+
 finish_test