Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -125,10 +125,11 @@
 */
 void sqlite3FinishCoding(Parse *pParse){
   sqlite3 *db;
   Vdbe *v;
 
+  assert( pParse->pToplevel==0 );
   db = pParse->db;
   if( db->mallocFailed ) return;
   if( pParse->nested ) return;
   if( pParse->nErr ) return;
 
@@ -3587,10 +3588,19 @@
 ** early in the code, before we know if any database tables will be used.
 */
 void sqlite3CodeVerifySchema(Parse *pParse, int iDb){
   Parse *pToplevel = sqlite3ParseToplevel(pParse);
 
+#ifndef SQLITE_OMIT_TRIGGER
+  if( pToplevel!=pParse ){
+    /* This branch is taken if a trigger is currently being coded. In this
+    ** case, set cookieGoto to a non-zero value to show that this function
+    ** has been called. This is used by the sqlite3ExprCodeConstants()
+    ** function. */
+    pParse->cookieGoto = -1;
+  }
+#endif
   if( pToplevel->cookieGoto==0 ){
     Vdbe *v = sqlite3GetVdbe(pToplevel);
     if( v==0 ) return;  /* This only happens if there was a prior error */
     pToplevel->cookieGoto = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0)+1;
   }

Index: src/trigger.c
==================================================================
--- src/trigger.c
+++ src/trigger.c
@@ -726,10 +726,19 @@
     **
     **   INSERT INTO t1 ... ;            -- insert into t2 uses REPLACE policy
     **   INSERT OR IGNORE INTO t1 ... ;  -- insert into t2 uses IGNORE policy
     */
     pParse->eOrconf = (orconf==OE_Default)?pStep->orconf:(u8)orconf;
+
+    /* Clear the cookieGoto flag. When coding triggers, the cookieGoto 
+    ** variable is used as a flag to indicate to sqlite3ExprCodeConstants()
+    ** that it is not safe to refactor constants (this happens after the
+    ** start of the first loop in the SQL statement is coded - at that 
+    ** point code may be conditionally executed, so it is no longer safe to 
+    ** initialize constant register values).  */
+    assert( pParse->cookieGoto==0 || pParse->cookieGoto==-1 );
+    pParse->cookieGoto = 0;
 
     switch( pStep->op ){
       case TK_UPDATE: {
         sqlite3Update(pParse, 
           targetSrcList(pParse, pStep),

Index: test/triggerC.test
==================================================================
--- test/triggerC.test
+++ test/triggerC.test
@@ -947,8 +947,50 @@
 } {}
 do_catchsql_test triggerC-13.2 {
   UPDATE t12 SET a=a+1, b=b+1;
 } {1 {too many levels of trigger recursion}}
 
+#-------------------------------------------------------------------------
+# The following tests seek to verify that constant values (i.e. literals)
+# are not factored out of loops within trigger programs. SQLite does
+# not factor constants out of loops within trigger programs as it may only
+# do so in code generated before the first table or index is opened. And
+# by the time a trigger program is coded, at least one table or index has
+# always been opened.
+#
+# At one point, due to a bug allowing constant factoring within triggers,
+# the following SQL would produce the wrong result.
+#
+set SQL {
+  CREATE TABLE t1(a, b, c);
+  CREATE INDEX i1 ON t1(a, c);
+  CREATE INDEX i2 ON t1(b, c);
+  INSERT INTO t1 VALUES(1, 2, 3);
+
+  CREATE TABLE t2(e, f);
+  CREATE INDEX i3 ON t2(e);
+  INSERT INTO t2 VALUES(1234567, 3);
+
+  CREATE TABLE empty(x);
+  CREATE TABLE not_empty(x);
+  INSERT INTO not_empty VALUES(2);
+
+  CREATE TABLE t4(x);
+  CREATE TABLE t5(g, h, i);
+
+  CREATE TRIGGER trig BEFORE INSERT ON t4 BEGIN
+    INSERT INTO t5 SELECT * FROM t1 WHERE 
+        (a IN (SELECT x FROM empty) OR b IN (SELECT x FROM not_empty)) 
+        AND c IN (SELECT f FROM t2 WHERE e=1234567);
+  END;
+
+  INSERT INTO t4 VALUES(0);
+  SELECT * FROM t5;
+}
 
+reset_db
+do_execsql_test triggerC-14.1 $SQL {1 2 3}
+reset_db
+optimization_control db factor-constants 0
+do_execsql_test triggerC-14.2 $SQL {1 2 3}
 
 finish_test