diff --git a/manifest b/manifest
index a1cf5d40b5..89c0690ce5 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Refactor\sthe\sfts3ColumnMethod()\sfunction\sso\sthat\sall\sbranches\scan\sbe\scovered.
-D 2017-04-18T05:49:23.863
+C Improved\soptimizations\sof\sviews\sas\sthe\sright\soperand\sof\sa\sLEFT\sJOIN.
+D 2017-04-18T11:20:19.836
 F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 6a8c838220f7c00820e1fc0ac1bccaaa8e5676067e1dbfa1bafa7a4ffecf8ae6
@@ -355,7 +355,7 @@ F src/ctime.c 47d91a25ad8f199a71a5b1b7b169d6dd0d6e98c5719eca801568798743d1161c
 F src/date.c ee676e7694dfadbdd2fde1a258a71be8360ba5ae
 F src/dbstat.c 19ee7a4e89979d4df8e44cfac7a8f905ec89b77d
 F src/delete.c 0d9d5549d42e79ce4d82ff1db1e6c81e36d2f67c
-F src/expr.c f6914d6d06c9a1e488f49cd51a0ef12d8073231e9c1a25c4c821262686cadcbf
+F src/expr.c f10e35dc50be4c8f82eb99bf5d8530229d1d60957cc3c9473ffe584d0444087c
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c db65492ae549c3b548c9ef1f279ce1684f1c473b116e1c56a90878cd5dcf968d
 F src/func.c 9d52522cc8ae7f5cdadfe14594262f1618bc1f86083c4cd6da861b4cf5af6174
@@ -391,7 +391,7 @@ F src/os_win.c 2a6c73eef01c51a048cc4ddccd57f981afbec18a
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c ff1232b3088a39806035ecfac4fffeb22717d80b
 F src/pager.h f2a99646c5533ffe11afa43e9e0bea74054e4efa
-F src/parse.y 48b03113704ee8bd78ee6996d81de7fbee22e105
+F src/parse.y 0513387ce02fea97897d8caef82d45f347818593f24f1bdc48e0c530a8af122d
 F src/pcache.c 62835bed959e2914edd26afadfecce29ece0e870
 F src/pcache.h 2cedcd8407eb23017d92790b112186886e179490
 F src/pcache1.c 1195a21fe28e223e024f900b2011e80df53793f0356a24caace4188b098540dc
@@ -402,7 +402,7 @@ F src/printf.c 8757834f1b54dae512fb25eb1acc8e94a0d15dd2290b58f2563f65973265adb2
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 3e518b962d932a997fae373366880fc028c75706
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
-F src/select.c 4588dcfb0fa430012247a209ba08e17904dd32ec7690e9cb6c85e0ef012b0518
+F src/select.c bf8ab605e49717c222136380453cfb7eda564f8e500d5ff6a01341ea59fefe80
 F src/shell.c 21b79c0e1b93f8e35fd7b4087d6ba438326c3d7e285d0dd51dfd741475f858a1
 F src/sqlite.h.in 40233103e3e4e10f8a63523498d0259d232e42aba478e2d3fb914799185aced6
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -463,13 +463,13 @@ F src/test_windirent.h 5d67483a55442e31e1bde0f4a230e6e932ad5906
 F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c 1003d6d90c6783206c711f0a9397656fa5b055209f4d092caa43bb3bf5215db5
-F src/treeview.c b92d57c1ac59f4a3f6b189506921a2b48098f6f4d6afd0b715bc2815ef6af092
+F src/treeview.c 6cf8d7fe9e63fae57dad1bb57f6615e14eac0c527e43d868e805042cae8ed1f7
 F src/trigger.c c9f0810043b265724fdb1bdd466894f984dfc182
 F src/update.c c443935c652af9365e033f756550b5032d02e1b06eb2cb890ed7511ae0c051dc
 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c
 F src/util.c ca8440ede81e155d15cff7c101654f60b55a9ae6
 F src/vacuum.c 1fe4555cd8c9b263afb85b5b4ee3a4a4181ad569
-F src/vdbe.c 11604e6c5d350a2c3b820130246c894de5a97d675a16f9825e88839fb9282eb3
+F src/vdbe.c 1eba07ffa0e4ff5e14ceca17e366c26f58c11d12cc56e55a9a13157a93533b7e
 F src/vdbe.h f7d1456e28875c2dcb964056589b5b7149ab7edf39edeca801596a39bb3d3848
 F src/vdbeInt.h c070bc5c8b913bda0ceaa995cd4d939ded5e4fc96cf7c3c1c602d41b871f8ade
 F src/vdbeapi.c 5b08d82592bcff4470601fe78aaabebd50837860
@@ -483,7 +483,7 @@ F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 40c543f0a2195d1b0dc88ef12142bea690009344
 F src/wal.h 06b2a0b599cc0f53ea97f497cf8c6b758c999f71
 F src/walker.c b71a992b413b3a022572eccf29ef4b4890223791
-F src/where.c 10ae856aa4bcf7c6be39b6b53422fc94e713ab8a19383b4cf525bc05ae70d872
+F src/where.c c6352f15be5031907c68bcbde96cad1a6da20e9f4051d10168a59235de9a8566
 F src/whereInt.h 2a4b634d63ce488b46d4b0da8f2eaa8f9aeab202bc25ef76f007de5e3fba1f20
 F src/wherecode.c 943e32e9dccd0af802e0683ae11071c8bd808364e5908a5fb66758bd404c8681
 F src/whereexpr.c e913aaa7b73ffcce66abcea5f197e2c538d48b5df78d0b7bba8ff4d73cc2e745
@@ -1487,7 +1487,7 @@ F test/zerodamage.test e59a56443d6298ecf7435f618f0b27654f0c849e
 F tool/GetFile.cs a15e08acb5dd7539b75ba23501581d7c2b462cb5
 F tool/GetTclKit.bat 6afa640edc7810725aec61c3076ac617c4aaf0b7
 F tool/Replace.cs 02c67258801c2fb5f63231e0ac0f220b4b36ba91
-F tool/addopcodes.tcl 10c889c4a65ec6c5604e4a47306fa77ff57ae189
+F tool/addopcodes.tcl edbd53806bf20e25af2373ad0c091be4385081c1aa1813b916bf093f94ed8380
 F tool/build-all-msvc.bat c12328d06c45fec8baada5949e3d5af54bf8c887 x
 F tool/build-shell.sh 950f47c6174f1eea171319438b93ba67ff5bf367
 F tool/cg_anno.tcl f95b0006c52cf7f0496b506343415b6ee3cdcdd3 x
@@ -1575,8 +1575,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5684525613961fed9db6a4d10dbe25521201b24f08e011df3a20ac895316957d
-Q +dd3217c38b507211d5102d00e3775e50e828762f6bcc97b1b087af11fd780f46
-R b7de56fa30910635d209a73e85c14a35
-U dan
-Z cc71176235299a67f61f3d9016204954
+P e47fdb493bd76d85f6f05771ee7a0b3ee31b1eb05839a60d2bdb47149ac692d8 3a5860d86fadcf924316707918bf283d26c53b1473e5e67f5cff59d18c2a7742
+R 78f4667b0ada8932854ad0b3e309cd92
+T +closed 3a5860d86fadcf924316707918bf283d26c53b1473e5e67f5cff59d18c2a7742
+U drh
+Z 119f88583d52d19e6e97c926524fc3c2
diff --git a/manifest.uuid b/manifest.uuid
index f16a0ec833..560bf633fe 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-e47fdb493bd76d85f6f05771ee7a0b3ee31b1eb05839a60d2bdb47149ac692d8
\ No newline at end of file
+41c27bc0ff1d3135cdb6273ede4595f5bb0c0e1e1d470ea1633cb525674cf431
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index ad17c5f229..873911633f 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -3889,6 +3889,17 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
       break;
     }
 
+    case TK_IF_NULL_ROW: {
+      int addrINR;
+      addrINR = sqlite3VdbeAddOp1(v, OP_IfNullRow, pExpr->iTable);
+      sqlite3ExprCachePush(pParse);
+      inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
+      sqlite3ExprCachePop(pParse);
+      sqlite3VdbeJumpHere(v, addrINR);
+      sqlite3VdbeChangeP3(v, addrINR, inReg);
+      break;
+    }
+
     /*
     ** Form A:
     **   CASE x WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
diff --git a/src/parse.y b/src/parse.y
index ef9d3dd0ec..522c805482 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -193,6 +193,23 @@ columnlist ::= columnlist COMMA columnname carglist.
 columnlist ::= columnname carglist.
 columnname(A) ::= nm(A) typetoken(Y). {sqlite3AddColumn(pParse,&A,&Y);}
 
+// The following directive causes tokens ABORT, AFTER, ASC, etc. to
+// fallback to ID if they will not parse as their original value.
+// This obviates the need for the "id" nonterminal.
+//
+%fallback ID
+  ABORT ACTION AFTER ANALYZE ASC ATTACH BEFORE BEGIN BY CASCADE CAST COLUMNKW
+  CONFLICT DATABASE DEFERRED DESC DETACH EACH END EXCLUSIVE EXPLAIN FAIL FOR
+  IGNORE IMMEDIATE INITIALLY INSTEAD LIKE_KW MATCH NO PLAN
+  QUERY KEY OF OFFSET PRAGMA RAISE RECURSIVE RELEASE REPLACE RESTRICT ROW
+  ROLLBACK SAVEPOINT TEMP TRIGGER VACUUM VIEW VIRTUAL WITH WITHOUT
+%ifdef SQLITE_OMIT_COMPOUND_SELECT
+  EXCEPT INTERSECT UNION
+%endif SQLITE_OMIT_COMPOUND_SELECT
+  REINDEX RENAME CTIME_KW IF
+  .
+%wildcard ANY.
+
 // Define operator precedence early so that this is the first occurrence
 // of the operator tokens in the grammer.  Keeping the operators together
 // causes them to be assigned integer values that are close together,
@@ -222,23 +239,6 @@ columnname(A) ::= nm(A) typetoken(Y). {sqlite3AddColumn(pParse,&A,&Y);}
 //
 %token_class id  ID|INDEXED.
 
-// The following directive causes tokens ABORT, AFTER, ASC, etc. to
-// fallback to ID if they will not parse as their original value.
-// This obviates the need for the "id" nonterminal.
-//
-%fallback ID
-  ABORT ACTION AFTER ANALYZE ASC ATTACH BEFORE BEGIN BY CASCADE CAST COLUMNKW
-  CONFLICT DATABASE DEFERRED DESC DETACH EACH END EXCLUSIVE EXPLAIN FAIL FOR
-  IGNORE IMMEDIATE INITIALLY INSTEAD LIKE_KW MATCH NO PLAN
-  QUERY KEY OF OFFSET PRAGMA RAISE RECURSIVE RELEASE REPLACE RESTRICT ROW
-  ROLLBACK SAVEPOINT TEMP TRIGGER VACUUM VIEW VIRTUAL WITH WITHOUT
-%ifdef SQLITE_OMIT_COMPOUND_SELECT
-  EXCEPT INTERSECT UNION
-%endif SQLITE_OMIT_COMPOUND_SELECT
-  REINDEX RENAME CTIME_KW IF
-  .
-%wildcard ANY.
-
 
 // And "ids" is an identifer-or-string.
 //
diff --git a/src/select.c b/src/select.c
index d7ba1f8068..3def13618e 100644
--- a/src/select.c
+++ b/src/select.c
@@ -3154,6 +3154,8 @@ static int multiSelectOrderBy(
 typedef struct SubstContext {
   Parse *pParse;            /* The parsing context */
   int iTable;               /* Replace references to this table */
+  int iNewTable;            /* New table number */
+  int isLeftJoin;           /* Add TK_IF_NULL_ROW opcodes on each replacement */
   ExprList *pEList;         /* Replacement expressions */
 } SubstContext;
 
@@ -3179,18 +3181,29 @@ static Expr *substExpr(
   Expr *pExpr            /* Expr in which substitution occurs */
 ){
   if( pExpr==0 ) return 0;
+  if( ExprHasProperty(pExpr, EP_FromJoin) && pExpr->iRightJoinTable==pSubst->iTable ){
+    pExpr->iRightJoinTable = pSubst->iNewTable;
+  }
   if( pExpr->op==TK_COLUMN && pExpr->iTable==pSubst->iTable ){
     if( pExpr->iColumn<0 ){
       pExpr->op = TK_NULL;
     }else{
       Expr *pNew;
       Expr *pCopy = pSubst->pEList->a[pExpr->iColumn].pExpr;
+      Expr ifNullRow;
       assert( pSubst->pEList!=0 && pExpr->iColumn<pSubst->pEList->nExpr );
       assert( pExpr->pLeft==0 && pExpr->pRight==0 );
       if( sqlite3ExprIsVector(pCopy) ){
         sqlite3VectorErrorMsg(pSubst->pParse, pCopy);
       }else{
         sqlite3 *db = pSubst->pParse->db;
+        if( pSubst->isLeftJoin && pCopy->op!=TK_COLUMN ){
+          memset(&ifNullRow, 0, sizeof(ifNullRow));
+          ifNullRow.op = TK_IF_NULL_ROW;
+          ifNullRow.pLeft = pCopy;
+          ifNullRow.iTable = pSubst->iNewTable;
+          pCopy = &ifNullRow;
+        }
         pNew = sqlite3ExprDup(db, pCopy, 0);
         if( pNew && (pExpr->flags & EP_FromJoin) ){
           pNew->iRightJoinTable = pExpr->iRightJoinTable;
@@ -3284,8 +3297,8 @@ static void substSelect(
 **        FROM-clause subquery that is a candidate for flattening.  (2b is
 **        due to ticket [2f7170d73bf9abf80] from 2015-02-09.)
 **
-**   (3)  The subquery is not the right operand of a left outer join
-**        (Originally ticket #306.  Strengthened by ticket #3300)
+**   (3)  The subquery is not the right operand of a LEFT JOIN
+**        or the subquery is not itself a join.
 **
 **   (4)  The subquery is not DISTINCT.
 **
@@ -3297,7 +3310,7 @@ static void substSelect(
 **        DISTINCT.
 **
 **   (7)  The subquery has a FROM clause.  TODO:  For subqueries without
-**        A FROM clause, consider adding a FROM close with the special
+**        A FROM clause, consider adding a FROM clause with the special
 **        table sqlite_once that consists of a single row containing a
 **        single NULL.
 **
@@ -3403,6 +3416,8 @@ static int flattenSubquery(
   SrcList *pSubSrc;   /* The FROM clause of the subquery */
   ExprList *pList;    /* The result set of the outer query */
   int iParent;        /* VDBE cursor number of the pSub result set temp table */
+  int iNewParent = -1;/* Replacement table for iParent */
+  int isLeftJoin = 0; /* True if pSub is the right side of a LEFT JOIN */    
   int i;              /* Loop counter */
   Expr *pWhere;                    /* The WHERE clause */
   struct SrcList_item *pSubitem;   /* The subquery */
@@ -3429,7 +3444,7 @@ static int flattenSubquery(
       return 0;                                          /* Restriction (2b)  */
     }
   }
-    
+
   pSubSrc = pSub->pSrc;
   assert( pSubSrc );
   /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
@@ -3467,10 +3482,9 @@ static int flattenSubquery(
     return 0; /* Restriction (23) */
   }
 
-  /* OBSOLETE COMMENT 1:
-  ** Restriction 3:  If the subquery is a join, make sure the subquery is 
-  ** not used as the right operand of an outer join.  Examples of why this
-  ** is not allowed:
+  /*
+  ** If the subquery is the right operand of a LEFT JOIN, then the
+  ** subquery may not be a join itself.  Example of why this is not allowed:
   **
   **         t1 LEFT OUTER JOIN (t2 JOIN t3)
   **
@@ -3480,27 +3494,13 @@ static int flattenSubquery(
   **
   ** which is not at all the same thing.
   **
-  ** OBSOLETE COMMENT 2:
-  ** Restriction 12:  If the subquery is the right operand of a left outer
-  ** join, make sure the subquery has no WHERE clause.
-  ** An examples of why this is not allowed:
-  **
-  **         t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
-  **
-  ** If we flatten the above, we would get
-  **
-  **         (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
-  **
-  ** But the t2.x>0 test will always fail on a NULL row of t2, which
-  ** effectively converts the OUTER JOIN into an INNER JOIN.
-  **
-  ** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
-  ** Ticket #3300 shows that flattening the right term of a LEFT JOIN
-  ** is fraught with danger.  Best to avoid the whole thing.  If the
-  ** subquery is the right term of a LEFT JOIN, then do not flatten.
+  ** See also tickets #306, #350, and #3300.
   */
   if( (pSubitem->fg.jointype & JT_OUTER)!=0 ){
-    return 0;
+    isLeftJoin = 1;
+    if( pSubSrc->nSrc>1 ){
+      return 0; /* Restriction (3) */
+    }
   }
 
   /* Restriction 17: If the sub-query is a compound SELECT, then it must
@@ -3709,6 +3709,7 @@ static int flattenSubquery(
       sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
       assert( pSrc->a[i+iFrom].fg.isTabFunc==0 );
       pSrc->a[i+iFrom] = pSubSrc->a[i];
+      iNewParent = pSubSrc->a[i].iCursor;
       memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
     }
     pSrc->a[iFrom].fg.jointype = jointype;
@@ -3754,6 +3755,9 @@ static int flattenSubquery(
       pSub->pOrderBy = 0;
     }
     pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
+    if( isLeftJoin ){
+      setJoinExpr(pWhere, iNewParent);
+    }
     if( subqueryIsAgg ){
       assert( pParent->pHaving==0 );
       pParent->pHaving = pParent->pWhere;
@@ -3770,6 +3774,8 @@ static int flattenSubquery(
       SubstContext x;
       x.pParse = pParse;
       x.iTable = iParent;
+      x.iNewTable = iNewParent;
+      x.isLeftJoin = isLeftJoin;
       x.pEList = pSub->pEList;
       substSelect(&x, pParent, 0);
     }
@@ -3878,6 +3884,8 @@ static int pushDownWhereTerms(
       pNew = sqlite3ExprDup(pParse->db, pWhere, 0);
       x.pParse = pParse;
       x.iTable = iCursor;
+      x.iNewTable = iCursor;
+      x.isLeftJoin = 0;
       x.pEList = pSubq->pEList;
       pNew = substExpr(&x, pNew);
       pSubq->pWhere = sqlite3ExprAnd(pParse->db, pSubq->pWhere, pNew);
diff --git a/src/treeview.c b/src/treeview.c
index e4f3d781ba..fc188256f9 100644
--- a/src/treeview.c
+++ b/src/treeview.c
@@ -470,6 +470,11 @@ void sqlite3TreeViewExpr(TreeView *pView, const Expr *pExpr, u8 moreToFollow){
       sqlite3TreeViewSelect(pView, pExpr->pLeft->x.pSelect, 0);
       break;
     }
+    case TK_IF_NULL_ROW: {
+      sqlite3TreeViewLine(pView, "IF-NULL-ROW %d", pExpr->iTable);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
     default: {
       sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
       break;
diff --git a/src/vdbe.c b/src/vdbe.c
index 8f0777e69d..5bed6f6f4e 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -2431,6 +2431,23 @@ case OP_NotNull: {            /* same as TK_NOTNULL, jump, in1 */
   break;
 }
 
+/* Opcode: IfNullRow P1 P2 P3 * *
+** Synopsis: if P1.nullRow then r[P3]=NULL, goto P2
+**
+** Check the cursor P1 to see if it is currently pointing at a NULL row.
+** If it is, then set register P3 to NULL and jump immediately to P2.
+** If P1 is not on a NULL row, then fall through without making any
+** changes.
+*/
+case OP_IfNullRow: {         /* jump */
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  if( p->apCsr[pOp->p1]->nullRow ){
+    sqlite3VdbeMemSetNull(aMem + pOp->p3);
+    goto jump_to_p2;
+  }
+  break;
+}
+
 /* Opcode: Column P1 P2 P3 P4 P5
 ** Synopsis: r[P3]=PX
 **
diff --git a/src/where.c b/src/where.c
index 50e4d7ce45..479e38d01c 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5009,6 +5009,8 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
         }else if( pOp->opcode==OP_Rowid ){
           pOp->p1 = pLevel->iIdxCur;
           pOp->opcode = OP_IdxRowid;
+        }else if( pOp->opcode==OP_IfNullRow ){
+          pOp->p1 = pLevel->iIdxCur;
         }
       }
     }
diff --git a/tool/addopcodes.tcl b/tool/addopcodes.tcl
index a6c58f1a25..308ddcb6bd 100644
--- a/tool/addopcodes.tcl
+++ b/tool/addopcodes.tcl
@@ -39,6 +39,7 @@ set extras {
   REGISTER
   VECTOR
   SELECT_COLUMN
+  IF_NULL_ROW
   ASTERISK
   SPAN
   SPACE