If a table is the right operand of a LEFT JOIN, then any column of that

table can be NULL even if that column as a NOT NULL constraint.
Fix for ticket [6f2222d550f5b0ee7ed].

FossilOrigin-Name: 6f6fcbe4736b9468a495c684d5eebc8bfe5c566a

src/expr.c

@@ -1414,7 +1414,8 @@ int sqlite3ExprCanBeNull(const Expr *p){
       return 0;
     case TK_COLUMN:
       assert( p->pTab!=0 );
-      return p->iColumn>=0 && p->pTab->aCol[p->iColumn].notNull==0;
+      return ExprHasProperty(p, EP_CanBeNull) ||
+             (p->iColumn>=0 && p->pTab->aCol[p->iColumn].notNull==0);
     default:
       return 1;
   }

src/resolve.c

@@ -320,6 +320,10 @@ static int lookupName(
       if( pMatch ){
         pExpr->iTable = pMatch->iCursor;
         pExpr->pTab = pMatch->pTab;
+        assert( (pMatch->jointype & JT_RIGHT)==0 ); /* RIGHT JOIN not (yet) supported */
+        if( (pMatch->jointype & JT_LEFT)!=0 ){
+          ExprSetProperty(pExpr, EP_CanBeNull);
+        }
         pSchema = pExpr->pTab->pSchema;
       }
     } /* if( pSrcList ) */

src/sqliteInt.h

@@ -2015,7 +2015,7 @@ struct Expr {
 /*
 ** The following are the meanings of bits in the Expr.flags field.
 */
-#define EP_FromJoin  0x000001 /* Originated in ON or USING clause of a join */
+#define EP_FromJoin  0x000001 /* Originates in ON/USING clause of outer join */
 #define EP_Agg       0x000002 /* Contains one or more aggregate functions */
 #define EP_Resolved  0x000004 /* IDs have been resolved to COLUMNs */
 #define EP_Error     0x000008 /* Expression contains one or more errors */
@@ -2035,6 +2035,7 @@ struct Expr {
 #define EP_NoReduce  0x020000 /* Cannot EXPRDUP_REDUCE this Expr */
 #define EP_Unlikely  0x040000 /* unlikely() or likelihood() function */
 #define EP_Constant  0x080000 /* Node is a constant */
+#define EP_CanBeNull 0x100000 /* Can be null despite NOT NULL constraint */
 
 /*
 ** These macros can be used to test, set, or clear bits in the