Add the ability to use indices for the first few terms of an ORDER BY clause,

then sort in batches to handle the later terms. FossilOrigin-Name: fa06a6fed9f48322d9b89721799ba12c46efa898
2025-11-14 00:22:38 +03:00 · 2014-03-21 20:58:42 +00:00
parent 8e1ee88c88 cc08fa48b8
commit 9a4444778f
18 changed files with 549 additions and 204 deletions
--- a/41
+++ b/41
@@ -1,5 +1,5 @@
-C Change\sthe\snames\sof\sSRT_DistTable\sand\sSRT_Table\sused\sby\sCTE\sto\smore\nmeaningful\sSRT_DistFifo\sand\sSRT_Fifo,\srespectively.\s\sSimplify\sthe\nIgnorableOrderby()\smacro\sin\sthe\sprocess.
-D 2014-03-21T19:56:09.443
+C Add\sthe\sability\sto\suse\sindices\sfor\sthe\sfirst\sfew\sterms\sof\san\sORDER\sBY\sclause,\nthen\ssort\sin\sbatches\sto\shandle\sthe\slater\sterms.
+D 2014-03-21T20:58:42.176
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -164,8 +164,8 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c a729e63cf5cd1829507cb7b8e89f99b95141bb53
 F src/bitvec.c 19a4ba637bd85f8f63fc8c9bae5ade9fb05ec1cb
 F src/btmutex.c 976f45a12e37293e32cae0281b15a21d48a8aaa7
-F src/btree.c 2a0e73f26c329f49e426237e71a879ffd205d778
-F src/btree.h da1b69b441ecee21f8b34ba73f0ae339540c4025
+F src/btree.c 029cec7b98fe0a985922c03f101630391044c4ad
+F src/btree.h 232836cb51753f2e96aa8ce0f052c6df850f76ba
 F src/btreeInt.h 0be66063468a520e4d66b80c7a1dc26d04ee6ea4
 F src/build.c 0d50ef95aad63f4c4fc47f3fa2670d4557c45db0
 F src/callback.c 174e3c8656bc29f91d710ab61550d16eea34be98
@@ -173,7 +173,7 @@ F src/complete.c dc1d136c0feee03c2f7550bafc0d29075e36deac
 F src/ctime.c 0231df905e2c4abba4483ee18ffc05adc321df2a
 F src/date.c 593c744b2623971e45affd0bde347631bdfa4625
 F src/delete.c cdd57149543bb28304d8f717c243f2a86b1fc280
-F src/expr.c 6e1e8bca468753f06758db7835a85e5408351e7a
+F src/expr.c da2b3cb41081af6b56e95e7c9e95949564ce2e21
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c 5269ef07b100763134f71b889327c333bd0989cf
 F src/func.c 2945bb2c4cdc0ac43733046285a4434310be1811
@@ -211,18 +211,18 @@ F src/parse.y 22d6a074e5f5a7258947a1dc55a9bf946b765dd0
 F src/pcache.c d8eafac28290d4bb80332005435db44991d07fc2
 F src/pcache.h a5e4f5d9f5d592051d91212c5949517971ae6222
 F src/pcache1.c 102e6f5a2fbc646154463eb856d1fd716867b64c
-F src/pragma.c e78b4bf2a267de2c17ee09f90b6807cf8d40e6a3
+F src/pragma.c 10f169b9650f0930a7a6df67e1387a4c2c449f38
 F src/prepare.c 677521ab7132615a8a26107a1d1c3132f44ae337
 F src/printf.c e5a0005f8b3de21f85da6a709d2fbee76775bf4b
 F src/random.c d10c1f85b6709ca97278428fd5db5bbb9c74eece
 F src/resolve.c 273d5f47c4e2c05b2d3d2bffeda939551ab59e66
 F src/rowset.c 64655f1a627c9c212d9ab497899e7424a34222e0
-F src/select.c cbee644f795a5fa14fa79bd760c3c9c883a6b4d8
+F src/select.c 633c56adeb382173d01016bea9e04e4dac54dfbc
 F src/shell.c cee9f46f2688a261601b1fd3d7f4b3cddf9b5cdf
 F src/sqlite.h.in a2ef671f92747a5a1c8a47bad5c585a8dd9eca80
 F src/sqlite3.rc 11094cc6a157a028b301a9f06b3d03089ea37c3e
 F src/sqlite3ext.h 886f5a34de171002ad46fae8c36a7d8051c190fc
-F src/sqliteInt.h 76b1cf0836f0d022aec5045474f5c6c90f7b9730
+F src/sqliteInt.h 1e16bac177ce6396e59af867afb90c92949895de
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 7ac05a5c7017d0b9f0b4bcd701228b784f987158
 F src/table.c 2cd62736f845d82200acfa1287e33feb3c15d62e
@@ -278,21 +278,21 @@ F src/update.c 5b3e74a03b3811e586b4f2b4cbd7c49f01c93115
 F src/utf.c 6dc9ec9f1b3db43ae8ba0365377f11df1ee4c01c
 F src/util.c c46c90459ef9bdc0c6c73803cf4c55425b4771cf
 F src/vacuum.c 3728d74919d4fb1356f9e9a13e27773db60b7179
-F src/vdbe.c 5f0fffa9bf49a90c05dc3d46d8217603fd0ee00e
+F src/vdbe.c 37cfae03a0c40515304fb0a8a1a97ac3aa965e87
 F src/vdbe.h fb2c48c198300a7c632f09fc940011d2ad2fc2ae
-F src/vdbeInt.h e54fc4f289fce48e81b3371128446033d097733b
+F src/vdbeInt.h 2b9a6849166d0014c843ae3fd83a062be4efa325
 F src/vdbeapi.c 0ed6053f947edd0b30f64ce5aeb811872a3450a4
-F src/vdbeaux.c e45e3f9daf38c5be3fd39e9aacc1c9066af57a06
+F src/vdbeaux.c 5078ca7de4fd5ba4535bd17fe44d5b56c2d3294c
 F src/vdbeblob.c 15377abfb59251bccedd5a9c7d014a895f0c04aa
 F src/vdbemem.c 6fc77594c60f6155404f3f8d71bf36d1fdeb4447
-F src/vdbesort.c 0fef5fa890fda760f92f293a5b0f2ccfe5d2dc55
+F src/vdbesort.c 4abb7c0f8f19b7d7d82f4558d5da1a30fdf9ea38
 F src/vdbetrace.c 6f52bc0c51e144b7efdcfb2a8f771167a8816767
 F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 76e7fc6de229bea8b30bb2539110f03a494dc3a8
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 11edb74d587bc87b33ca96a5173e3ec1b8389e45
-F src/where.c eed0b83bd7ffef4ac2f7a2fcc9dcfa66b18b8b9e
-F src/whereInt.h 921f935af8b684ffb49705610bda7284db1db138
+F src/where.c f394453e4960462e62671158199f060ac956f8bc
+F src/whereInt.h 2564055b440e44ebec8b47f237bbccae6719b7af
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 45c0201e28045ad38a530b5a144b73cd4aa2cfd6
@@ -431,7 +431,7 @@ F test/descidx1.test 6d03b44c8538fe0eb4924e19fba10cdd8f3c9240
 F test/descidx2.test 9f1a0c83fd57f8667c82310ca21b30a350888b5d
 F test/descidx3.test 09ddbe3f5295f482d2f8b687cf6db8bad7acd9a2
 F test/diskfull.test 106391384780753ea6896b7b4f005d10e9866b6e
-F test/distinct.test c7b194ef95dbddb32d77acbbab2e023c6eed0cb2
+F test/distinct.test 086e70c765f172e8974e9f83b9ac5ca03c154e77
 F test/distinctagg.test 1a6ef9c87a58669438fc771450d7a72577417376
 F test/e_createtable.test ee95d48664503d40f6cc9ef4a7d03216188e2ada
 F test/e_delete.test d5186e2f5478b659f16a2c8b66c09892823e542a
@@ -722,7 +722,8 @@ F test/orderby1.test 9b524aff9147288da43a6d7ddfdcff47fa2303c6
 F test/orderby2.test bc11009f7cd99d96b1b11e57b199b00633eb5b04
 F test/orderby3.test 8619d06a3debdcd80a27c0fdea5c40b468854b99
 F test/orderby4.test 4d39bfbaaa3ae64d026ca2ff166353d2edca4ba4
-F test/orderby5.test 0eb82d5890c3f3d0563966560cfdc984ea69e30c
+F test/orderby5.test 2490183fef54417209d1df253633a605d46bd350
+F test/orderby6.test 8b38138ab0972588240b3fca0985d2e400432859
 F test/oserror.test 50417780d0e0d7cd23cf12a8277bb44024765df3
 F test/pager1.test 1acbdb14c5952a72dd43129cabdbf69aaa3ed1fa
 F test/pager2.test 67b8f40ae98112bcdba1f2b2d03ea83266418c71
@@ -1089,7 +1090,7 @@ F test/whereC.test d6f4ecd4fa2d9429681a5b22a25d2bda8e86ab8a
 F test/whereD.test 6c2feb79ef1f68381b07f39017fe5f9b96da8d62
 F test/whereE.test b3a055eef928c992b0a33198a7b8dc10eea5ad2f
 F test/whereF.test 5b2ba0dbe8074aa13e416b37c753991f0a2492d7
-F test/whereG.test 2a3d5181decc801b36600fa1c40b0dad2ccc267f
+F test/whereG.test eb3a46b3eaf38e25e3013433b2db8a25a866c215
 F test/wherelimit.test 5e9fd41e79bb2b2d588ed999d641d9c965619b31
 F test/wild001.test bca33f499866f04c24510d74baf1e578d4e44b1c
 F test/win32heap.test ea19770974795cff26e11575e12d422dbd16893c
@@ -1156,7 +1157,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P 1f413aca00015100224273480e1ce39a76bf93ab
-R 26118dcbaf585402aab527afe8f97345
+P 45d8cc678d128f1dda6469864215a8ed9de4366a 71e9ae72c272dc86720b2bfe719f57de437c400b
+R 3371108f475a5908c384cc490e83cfb1
 U drh
-Z d7e9ffdc5a42e976a5961e8287a0561b
+Z 76333cbbd5592a854905d3a7e7bd7626
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-45d8cc678d128f1dda6469864215a8ed9de4366a
+fa06a6fed9f48322d9b89721799ba12c46efa898
--- a/src/btree.c
+++ b/src/btree.c
@@ -7425,6 +7425,15 @@ int sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
  return rc;
 }

+/*
+** Delete all information from the single table that pCur is open on.
+**
+** This routine only work for pCur on an ephemeral table.
+*/
+int sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
+  return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
+}
+
 /*
 ** Erase all information in a table and add the root of the table to
 ** the freelist.  Except, the root of the principle table (the one on
--- a/src/btree.h
+++ b/src/btree.h
@@ -115,6 +115,7 @@ int sqlite3BtreeIncrVacuum(Btree *);

 int sqlite3BtreeDropTable(Btree*, int, int*);
 int sqlite3BtreeClearTable(Btree*, int, int*);
+int sqlite3BtreeClearTableOfCursor(BtCursor*);
 void sqlite3BtreeTripAllCursors(Btree*, int);

 void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
--- a/src/expr.c
+++ b/src/expr.c
@@ -955,7 +955,6 @@ ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
  if( p==0 ) return 0;
  pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );
  if( pNew==0 ) return 0;
-  pNew->iECursor = 0;
  pNew->nExpr = i = p->nExpr;
  if( (flags & EXPRDUP_REDUCE)==0 ) for(i=1; i<p->nExpr; i+=i){}
  pNew->a = pItem = sqlite3DbMallocRaw(db,  i*sizeof(p->a[0]) );
@@ -1068,7 +1067,6 @@ Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
  pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
-  pNew->addrOpenEphm[2] = -1;
  pNew->nSelectRow = p->nSelectRow;
  pNew->pWith = withDup(db, p->pWith);
  return pNew;
@@ -2340,7 +2338,7 @@ void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
  int i;
  struct yColCache *p;
  assert( iFrom>=iTo+nReg || iFrom+nReg<=iTo );
-  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg-1);
+  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int x = p->iReg;
    if( x>=iFrom && x<iFrom+nReg ){
@@ -2741,7 +2739,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
        }

        sqlite3ExprCachePush(pParse);     /* Ticket 2ea2425d34be */
-        sqlite3ExprCodeExprList(pParse, pFarg, r1, 
+        sqlite3ExprCodeExprList(pParse, pFarg, r1,
                                SQLITE_ECEL_DUP|SQLITE_ECEL_FACTOR);
        sqlite3ExprCachePop(pParse, 1);   /* Ticket 2ea2425d34be */
      }else{
--- a/src/pragma.c
+++ b/src/pragma.c
@@ -1875,7 +1875,7 @@ void sqlite3Pragma(
      sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
         sqlite3MPrintf(db, "*** in database %s ***\n", db->aDb[i].zName),
         P4_DYNAMIC);
-      sqlite3VdbeAddOp2(v, OP_Move, 2, 4);
+      sqlite3VdbeAddOp3(v, OP_Move, 2, 4, 1);
      sqlite3VdbeAddOp3(v, OP_Concat, 4, 3, 2);
      sqlite3VdbeAddOp2(v, OP_ResultRow, 2, 1);
      sqlite3VdbeJumpHere(v, addr);
--- a/src/select.c
+++ b/src/select.c
@@ -14,6 +14,34 @@
 */
 #include "sqliteInt.h"

+/*
+** An instance of the following object is used to record information about
+** how to process the DISTINCT keyword, to simplify passing that information
+** into the selectInnerLoop() routine.
+*/
+typedef struct DistinctCtx DistinctCtx;
+struct DistinctCtx {
+  u8 isTnct;      /* True if the DISTINCT keyword is present */
+  u8 eTnctType;   /* One of the WHERE_DISTINCT_* operators */
+  int tabTnct;    /* Ephemeral table used for DISTINCT processing */
+  int addrTnct;   /* Address of OP_OpenEphemeral opcode for tabTnct */
+};
+
+/*
+** An instance of the following object is used to record information about
+** the ORDER BY (or GROUP BY) clause of query is being coded.
+*/
+typedef struct SortCtx SortCtx;
+struct SortCtx {
+  ExprList *pOrderBy;   /* The ORDER BY (or GROUP BY clause) */
+  int nOBSat;           /* Number of ORDER BY terms satisfied by indices */
+  int iECursor;         /* Cursor number for the sorter */
+  int regReturn;        /* Register holding block-output return address */
+  int labelBkOut;       /* Start label for the block-output subroutine */
+  int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
+  u8 sortFlags;         /* Zero or more SORTFLAG_* bits */
+};
+#define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */

 /*
 ** Delete all the content of a Select structure but do not deallocate
@@ -87,7 +115,6 @@ Select *sqlite3SelectNew(
  assert( pOffset==0 || pLimit!=0 );
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
-  pNew->addrOpenEphm[2] = -1;
  if( db->mallocFailed ) {
    clearSelect(db, pNew);
    if( pNew!=&standin ) sqlite3DbFree(db, pNew);
@@ -419,34 +446,71 @@ static int sqliteProcessJoin(Parse *pParse, Select *p){
  return 0;
 }

+/* Forward reference */
+static KeyInfo *keyInfoFromExprList(
+  Parse *pParse,       /* Parsing context */
+  ExprList *pList,     /* Form the KeyInfo object from this ExprList */
+  int iStart,          /* Begin with this column of pList */
+  int nExtra           /* Add this many extra columns to the end */
+);
+
 /*
-** Insert code into "v" that will push the record on the top of the
-** stack into the sorter.
+** Insert code into "v" that will push the record in register regData
+** into the sorter.
 */
 static void pushOntoSorter(
  Parse *pParse,         /* Parser context */
-  ExprList *pOrderBy,    /* The ORDER BY clause */
+  SortCtx *pSort,        /* Information about the ORDER BY clause */
  Select *pSelect,       /* The whole SELECT statement */
  int regData            /* Register holding data to be sorted */
 ){
  Vdbe *v = pParse->pVdbe;
-  int nExpr = pOrderBy->nExpr;
+  int nExpr = pSort->pOrderBy->nExpr;
  int regBase = sqlite3GetTempRange(pParse, nExpr+2);
  int regRecord = sqlite3GetTempReg(pParse);
+  int nOBSat = pSort->nOBSat;
  int op;
  sqlite3ExprCacheClear(pParse);
-  sqlite3ExprCodeExprList(pParse, pOrderBy, regBase, 0);
-  sqlite3VdbeAddOp2(v, OP_Sequence, pOrderBy->iECursor, regBase+nExpr);
+  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, 0);
+  sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
  sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
-  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
-  if( pSelect->selFlags & SF_UseSorter ){
+  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nExpr+2-nOBSat, regRecord);
+  if( nOBSat>0 ){
+    int regPrevKey;   /* The first nOBSat columns of the previous row */
+    int addrFirst;    /* Address of the OP_IfNot opcode */
+    int addrJmp;      /* Address of the OP_Jump opcode */
+    VdbeOp *pOp;      /* Opcode that opens the sorter */
+    int nKey;         /* Number of sorting key columns, including OP_Sequence */
+
+    regPrevKey = pParse->nMem+1;
+    pParse->nMem += pSort->nOBSat;
+    nKey = nExpr - pSort->nOBSat + 1;
+    addrFirst = sqlite3VdbeAddOp1(v, OP_IfNot, regBase+nExpr); VdbeCoverage(v);
+    sqlite3VdbeAddOp3(v, OP_Compare, regPrevKey, regBase, pSort->nOBSat);
+    pOp = sqlite3VdbeGetOp(v, pSort->addrSortIndex);
+    pOp->p2 = nKey + 1;
+    sqlite3VdbeChangeP4(v, -1, (char*)pOp->p4.pKeyInfo, P4_KEYINFO);
+    pOp->p4.pKeyInfo = keyInfoFromExprList(pParse, pSort->pOrderBy, nOBSat, 1);
+    addrJmp = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp3(v, OP_Jump, addrJmp+1, 0, addrJmp+1); VdbeCoverage(v);
+    pSort->labelBkOut = sqlite3VdbeMakeLabel(v);
+    pSort->regReturn = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
+    sqlite3VdbeAddOp1(v, OP_ResetSorter, pSort->iECursor);
+    sqlite3VdbeJumpHere(v, addrFirst);
+    sqlite3VdbeAddOp3(v, OP_Move, regBase, regPrevKey, pSort->nOBSat);
+    sqlite3VdbeJumpHere(v, addrJmp);
+  }
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
-  sqlite3VdbeAddOp2(v, op, pOrderBy->iECursor, regRecord);
-  sqlite3ReleaseTempReg(pParse, regRecord);
-  sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
+  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
+  if( nOBSat==0 ){
+    sqlite3ReleaseTempReg(pParse, regRecord);
+    sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
+  }
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
@@ -459,8 +523,8 @@ static void pushOntoSorter(
    sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
    addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, addr1);
-    sqlite3VdbeAddOp1(v, OP_Last, pOrderBy->iECursor);
-    sqlite3VdbeAddOp1(v, OP_Delete, pOrderBy->iECursor);
+    sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
+    sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
    sqlite3VdbeJumpHere(v, addr2);
  }
 }
@@ -534,19 +598,6 @@ static int checkForMultiColumnSelectError(
 }
 #endif

-/*
-** An instance of the following object is used to record information about
-** how to process the DISTINCT keyword, to simplify passing that information
-** into the selectInnerLoop() routine.
-*/
-typedef struct DistinctCtx DistinctCtx;
-struct DistinctCtx {
-  u8 isTnct;      /* True if the DISTINCT keyword is present */
-  u8 eTnctType;   /* One of the WHERE_DISTINCT_* operators */
-  int tabTnct;    /* Ephemeral table used for DISTINCT processing */
-  int addrTnct;   /* Address of OP_OpenEphemeral opcode for tabTnct */
-};
-
 /*
 ** This routine generates the code for the inside of the inner loop
 ** of a SELECT.
@@ -561,7 +612,7 @@ static void selectInnerLoop(
  Select *p,              /* The complete select statement being coded */
  ExprList *pEList,       /* List of values being extracted */
  int srcTab,             /* Pull data from this table */
-  ExprList *pOrderBy,     /* If not NULL, sort results using this key */
+  SortCtx *pSort,         /* If not NULL, info on how to process ORDER BY */
  DistinctCtx *pDistinct, /* If not NULL, info on how to process DISTINCT */
  SelectDest *pDest,      /* How to dispose of the results */
  int iContinue,          /* Jump here to continue with next row */
@@ -578,7 +629,8 @@ static void selectInnerLoop(
  assert( v );
  assert( pEList!=0 );
  hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
-  if( pOrderBy==0 && !hasDistinct ){
+  if( pSort && pSort->pOrderBy==0 ) pSort = 0;
+  if( pSort==0 && !hasDistinct ){
    assert( iContinue!=0 );
    codeOffset(v, p->iOffset, iContinue);
  }
@@ -669,7 +721,7 @@ static void selectInnerLoop(
        break;
      }
    }
-    if( pOrderBy==0 ){
+    if( pSort==0 ){
      codeOffset(v, p->iOffset, iContinue);
    }
  }
@@ -718,11 +770,11 @@ static void selectInnerLoop(
        int addr = sqlite3VdbeCurrentAddr(v) + 4;
        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0); VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
-        assert( pOrderBy==0 );
+        assert( pSort==0 );
      }
 #endif
-      if( pOrderBy ){
-        pushOntoSorter(pParse, pOrderBy, p, r1);
+      if( pSort ){
+        pushOntoSorter(pParse, pSort, p, r1);
      }else{
        int r2 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
@@ -743,12 +795,12 @@ static void selectInnerLoop(
      assert( nResultCol==1 );
      pDest->affSdst =
                  sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affSdst);
-      if( pOrderBy ){
+      if( pSort ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
-        pushOntoSorter(pParse, pOrderBy, p, regResult);
+        pushOntoSorter(pParse, pSort, p, regResult);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult,1,r1, &pDest->affSdst, 1);
@@ -773,8 +825,8 @@ static void selectInnerLoop(
    */
    case SRT_Mem: {
      assert( nResultCol==1 );
-      if( pOrderBy ){
-        pushOntoSorter(pParse, pOrderBy, p, regResult);
+      if( pSort ){
+        pushOntoSorter(pParse, pSort, p, regResult);
      }else{
        sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
        /* The LIMIT clause will jump out of the loop for us */
@@ -787,10 +839,10 @@ static void selectInnerLoop(
    case SRT_Output: {        /* Return the results */
      testcase( eDest==SRT_Coroutine );
      testcase( eDest==SRT_Output );
-      if( pOrderBy ){
+      if( pSort ){
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1);
-        pushOntoSorter(pParse, pOrderBy, p, r1);
+        pushOntoSorter(pParse, pSort, p, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }else if( eDest==SRT_Coroutine ){
        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
@@ -867,7 +919,7 @@ static void selectInnerLoop(
  ** there is a sorter, in which case the sorter has already limited
  ** the output for us.
  */
-  if( pOrderBy==0 && p->iLimit ){
+  if( pSort==0 && p->iLimit ){
    sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1); VdbeCoverage(v);
  }
 }
@@ -938,7 +990,12 @@ int sqlite3KeyInfoIsWriteable(KeyInfo *p){ return p->nRef==1; }
 ** function is responsible for seeing that this structure is eventually
 ** freed.
 */
-static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList, int nExtra){
+static KeyInfo *keyInfoFromExprList(
+  Parse *pParse,       /* Parsing context */
+  ExprList *pList,     /* Form the KeyInfo object from this ExprList */
+  int iStart,          /* Begin with this column of pList */
+  int nExtra           /* Add this many extra columns to the end */
+){
  int nExpr;
  KeyInfo *pInfo;
  struct ExprList_item *pItem;
@@ -946,15 +1003,15 @@ static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList, int nExtra){
  int i;

  nExpr = pList->nExpr;
-  pInfo = sqlite3KeyInfoAlloc(db, nExpr+nExtra, 1);
+  pInfo = sqlite3KeyInfoAlloc(db, nExpr+nExtra-iStart, 1);
  if( pInfo ){
    assert( sqlite3KeyInfoIsWriteable(pInfo) );
-    for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
+    for(i=iStart, pItem=pList->a+iStart; i<nExpr; i++, pItem++){
      CollSeq *pColl;
      pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
      if( !pColl ) pColl = db->pDfltColl;
-      pInfo->aColl[i] = pColl;
-      pInfo->aSortOrder[i] = pItem->sortOrder;
+      pInfo->aColl[i-iStart] = pColl;
+      pInfo->aSortOrder[i-iStart] = pItem->sortOrder;
    }
  }
  return pInfo;
@@ -1056,24 +1113,31 @@ static void explainComposite(
 static void generateSortTail(
  Parse *pParse,    /* Parsing context */
  Select *p,        /* The SELECT statement */
-  Vdbe *v,          /* Generate code into this VDBE */
+  SortCtx *pSort,   /* Information on the ORDER BY clause */
  int nColumn,      /* Number of columns of data */
  SelectDest *pDest /* Write the sorted results here */
 ){
+  Vdbe *v = pParse->pVdbe;                     /* The prepared statement */
  int addrBreak = sqlite3VdbeMakeLabel(v);     /* Jump here to exit loop */
  int addrContinue = sqlite3VdbeMakeLabel(v);  /* Jump here for next cycle */
  int addr;
+  int addrOnce = 0;
  int iTab;
  int pseudoTab = 0;
-  ExprList *pOrderBy = p->pOrderBy;
-
+  ExprList *pOrderBy = pSort->pOrderBy;
  int eDest = pDest->eDest;
  int iParm = pDest->iSDParm;
-
  int regRow;
  int regRowid;
+  int nKey;

-  iTab = pOrderBy->iECursor;
+  if( pSort->labelBkOut ){
+    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrBreak);
+    sqlite3VdbeResolveLabel(v, pSort->labelBkOut);
+    addrOnce = sqlite3CodeOnce(pParse); VdbeCoverage(v);
+  }
+  iTab = pSort->iECursor;
  regRow = sqlite3GetTempReg(pParse);
  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
    pseudoTab = pParse->nTab++;
@@ -1082,20 +1146,23 @@ static void generateSortTail(
  }else{
    regRowid = sqlite3GetTempReg(pParse);
  }
-  if( p->selFlags & SF_UseSorter ){
+  nKey = pOrderBy->nExpr - pSort->nOBSat;
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    int regSortOut = ++pParse->nMem;
    int ptab2 = pParse->nTab++;
-    sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, pOrderBy->nExpr+2);
+    sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, nKey+2);
+    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
    addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
    VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
    sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
-    sqlite3VdbeAddOp3(v, OP_Column, ptab2, pOrderBy->nExpr+1, regRow);
+    sqlite3VdbeAddOp3(v, OP_Column, ptab2, nKey+1, regRow);
    sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
  }else{
+    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
    addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak); VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
-    sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr+1, regRow);
+    sqlite3VdbeAddOp3(v, OP_Column, iTab, nKey+1, regRow);
  }
  switch( eDest ){
    case SRT_Table:
@@ -1150,11 +1217,12 @@ static void generateSortTail(
  /* The bottom of the loop
  */
  sqlite3VdbeResolveLabel(v, addrContinue);
-  if( p->selFlags & SF_UseSorter ){
+  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    sqlite3VdbeAddOp2(v, OP_SorterNext, iTab, addr); VdbeCoverage(v);
  }else{
    sqlite3VdbeAddOp2(v, OP_Next, iTab, addr); VdbeCoverage(v);
  }
+  if( pSort->regReturn ) sqlite3VdbeAddOp1(v, OP_Return, pSort->regReturn);
  sqlite3VdbeResolveLabel(v, addrBreak);
  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
    sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
@@ -4312,7 +4380,7 @@ static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
           "argument");
        pFunc->iDistinct = -1;
      }else{
-        KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList, 0);
+        KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList, 0, 0);
        sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
                          (char*)pKeyInfo, P4_KEYINFO);
      }
@@ -4467,12 +4535,11 @@ int sqlite3Select(
  ExprList *pEList;      /* List of columns to extract. */
  SrcList *pTabList;     /* List of tables to select from */
  Expr *pWhere;          /* The WHERE clause.  May be NULL */
-  ExprList *pOrderBy;    /* The ORDER BY clause.  May be NULL */
  ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
  Expr *pHaving;         /* The HAVING clause.  May be NULL */
  int rc = 1;            /* Value to return from this function */
-  int addrSortIndex;     /* Address of an OP_OpenEphemeral instruction */
  DistinctCtx sDistinct; /* Info on how to code the DISTINCT keyword */
+  SortCtx sSort;         /* Info on how to code the ORDER BY clause */
  AggInfo sAggInfo;      /* Information used by aggregate queries */
  int iEnd;              /* Address of the end of the query */
  sqlite3 *db;           /* The database connection */
@@ -4505,7 +4572,8 @@ int sqlite3Select(
    p->selFlags &= ~SF_Distinct;
  }
  sqlite3SelectPrep(pParse, p, 0);
-  pOrderBy = p->pOrderBy;
+  memset(&sSort, 0, sizeof(sSort));
+  sSort.pOrderBy = p->pOrderBy;
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( pParse->nErr || db->mallocFailed ){
@@ -4627,7 +4695,7 @@ int sqlite3Select(
    pParse->nHeight -= sqlite3SelectExprHeight(p);
    pTabList = p->pSrc;
    if( !IgnorableOrderby(pDest) ){
-      pOrderBy = p->pOrderBy;
+      sSort.pOrderBy = p->pOrderBy;
    }
  }
  pEList = p->pEList;
@@ -4654,9 +4722,9 @@ int sqlite3Select(
  ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
  ** to disable this optimization for testing purposes.
  */
-  if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy, -1)==0
+  if( sqlite3ExprListCompare(p->pGroupBy, sSort.pOrderBy, -1)==0
         && OptimizationEnabled(db, SQLITE_GroupByOrder) ){
-    pOrderBy = 0;
+    sSort.pOrderBy = 0;
  }

  /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and 
@@ -4675,12 +4743,12 @@ int sqlite3Select(
  ** BY and DISTINCT, and an index or separate temp-table for the other.
  */
  if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct 
-   && sqlite3ExprListCompare(pOrderBy, p->pEList, -1)==0
+   && sqlite3ExprListCompare(sSort.pOrderBy, p->pEList, -1)==0
  ){
    p->selFlags &= ~SF_Distinct;
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
    pGroupBy = p->pGroupBy;
-    pOrderBy = 0;
+    sSort.pOrderBy = 0;
    /* Notice that even thought SF_Distinct has been cleared from p->selFlags,
    ** the sDistinct.isTnct is still set.  Hence, isTnct represents the
    ** original setting of the SF_Distinct flag, not the current setting */
@@ -4694,16 +4762,16 @@ int sqlite3Select(
  ** we figure out that the sorting index is not needed.  The addrSortIndex
  ** variable is used to facilitate that change.
  */
-  if( pOrderBy ){
+  if( sSort.pOrderBy ){
    KeyInfo *pKeyInfo;
-    pKeyInfo = keyInfoFromExprList(pParse, pOrderBy, 0);
-    pOrderBy->iECursor = pParse->nTab++;
-    p->addrOpenEphm[2] = addrSortIndex =
+    pKeyInfo = keyInfoFromExprList(pParse, sSort.pOrderBy, 0, 0);
+    sSort.iECursor = pParse->nTab++;
+    sSort.addrSortIndex =
      sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
-                           pOrderBy->iECursor, pOrderBy->nExpr+2, 0,
+                           sSort.iECursor, sSort.pOrderBy->nExpr+2, 0,
                           (char*)pKeyInfo, P4_KEYINFO);
  }else{
-    addrSortIndex = -1;
+    sSort.addrSortIndex = -1;
  }

  /* If the output is destined for a temporary table, open that table.
@@ -4717,9 +4785,9 @@ int sqlite3Select(
  iEnd = sqlite3VdbeMakeLabel(v);
  p->nSelectRow = LARGEST_INT64;
  computeLimitRegisters(pParse, p, iEnd);
-  if( p->iLimit==0 && addrSortIndex>=0 ){
-    sqlite3VdbeGetOp(v, addrSortIndex)->opcode = OP_SorterOpen;
-    p->selFlags |= SF_UseSorter;
+  if( p->iLimit==0 && sSort.addrSortIndex>=0 ){
+    sqlite3VdbeGetOp(v, sSort.addrSortIndex)->opcode = OP_SorterOpen;
+    sSort.sortFlags |= SORTFLAG_UseSorter;
  }

  /* Open a virtual index to use for the distinct set.
@@ -4728,7 +4796,7 @@ int sqlite3Select(
    sDistinct.tabTnct = pParse->nTab++;
    sDistinct.addrTnct = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
                                sDistinct.tabTnct, 0, 0,
-                                (char*)keyInfoFromExprList(pParse, p->pEList, 0),
+                                (char*)keyInfoFromExprList(pParse, p->pEList,0,0),
                                P4_KEYINFO);
    sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
    sDistinct.eTnctType = WHERE_DISTINCT_UNORDERED;
@@ -4741,8 +4809,8 @@ int sqlite3Select(
    u16 wctrlFlags = (sDistinct.isTnct ? WHERE_WANT_DISTINCT : 0);

    /* Begin the database scan. */
-    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pOrderBy, p->pEList,
-                               wctrlFlags, 0);
+    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, sSort.pOrderBy,
+                               p->pEList, wctrlFlags, 0);
    if( pWInfo==0 ) goto select_end;
    if( sqlite3WhereOutputRowCount(pWInfo) < p->nSelectRow ){
      p->nSelectRow = sqlite3WhereOutputRowCount(pWInfo);
@@ -4750,19 +4818,23 @@ int sqlite3Select(
    if( sDistinct.isTnct && sqlite3WhereIsDistinct(pWInfo) ){
      sDistinct.eTnctType = sqlite3WhereIsDistinct(pWInfo);
    }
-    if( pOrderBy && sqlite3WhereIsOrdered(pWInfo) ) pOrderBy = 0;
+    if( sSort.pOrderBy ){
+      sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);
+      if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
+        sSort.pOrderBy = 0;
+      }
+    }

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral
    ** into an OP_Noop.
    */
-    if( addrSortIndex>=0 && pOrderBy==0 ){
-      sqlite3VdbeChangeToNoop(v, addrSortIndex);
-      p->addrOpenEphm[2] = -1;
+    if( sSort.addrSortIndex>=0 && sSort.pOrderBy==0 ){
+      sqlite3VdbeChangeToNoop(v, sSort.addrSortIndex);
    }

    /* Use the standard inner loop. */
-    selectInnerLoop(pParse, p, pEList, -1, pOrderBy, &sDistinct, pDest,
+    selectInnerLoop(pParse, p, pEList, -1, &sSort, &sDistinct, pDest,
                    sqlite3WhereContinueLabel(pWInfo),
                    sqlite3WhereBreakLabel(pWInfo));

@@ -4818,7 +4890,7 @@ int sqlite3Select(
    sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
    sAggInfo.pGroupBy = pGroupBy;
    sqlite3ExprAnalyzeAggList(&sNC, pEList);
-    sqlite3ExprAnalyzeAggList(&sNC, pOrderBy);
+    sqlite3ExprAnalyzeAggList(&sNC, sSort.pOrderBy);
    if( pHaving ){
      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
    }
@@ -4852,7 +4924,7 @@ int sqlite3Select(
      ** will be converted into a Noop.  
      */
      sAggInfo.sortingIdx = pParse->nTab++;
-      pKeyInfo = keyInfoFromExprList(pParse, pGroupBy, 0);
+      pKeyInfo = keyInfoFromExprList(pParse, pGroupBy, 0, 0);
      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen, 
          sAggInfo.sortingIdx, sAggInfo.nSortingColumn, 
          0, (char*)pKeyInfo, P4_KEYINFO);
@@ -4881,10 +4953,10 @@ int sqlite3Select(
      ** in the right order to begin with.
      */
      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
-      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pGroupBy, 0, 
+      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pGroupBy, 0,
                                 WHERE_GROUPBY, 0);
      if( pWInfo==0 ) goto select_end;
-      if( sqlite3WhereIsOrdered(pWInfo) ){
+      if( sqlite3WhereIsOrdered(pWInfo)==pGroupBy->nExpr ){
        /* The optimizer is able to deliver rows in group by order so
        ** we do not have to sort.  The OP_OpenEphemeral table will be
        ** cancelled later because we still need to use the pKeyInfo
@@ -5035,7 +5107,7 @@ int sqlite3Select(
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      finalizeAggFunctions(pParse, &sAggInfo);
      sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
-      selectInnerLoop(pParse, p, p->pEList, -1, pOrderBy,
+      selectInnerLoop(pParse, p, p->pEList, -1, &sSort,
                      &sDistinct, pDest,
                      addrOutputRow+1, addrSetAbort);
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
@@ -5167,7 +5239,7 @@ int sqlite3Select(
        }
        updateAccumulator(pParse, &sAggInfo);
        assert( pMinMax==0 || pMinMax->nExpr==1 );
-        if( sqlite3WhereIsOrdered(pWInfo) ){
+        if( sqlite3WhereIsOrdered(pWInfo)>0 ){
          sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3WhereBreakLabel(pWInfo));
          VdbeComment((v, "%s() by index",
                (flag==WHERE_ORDERBY_MIN?"min":"max")));
@@ -5176,7 +5248,7 @@ int sqlite3Select(
        finalizeAggFunctions(pParse, &sAggInfo);
      }

-      pOrderBy = 0;
+      sSort.pOrderBy = 0;
      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
      selectInnerLoop(pParse, p, p->pEList, -1, 0, 0, 
                      pDest, addrEnd, addrEnd);
@@ -5193,9 +5265,9 @@ int sqlite3Select(
  /* If there is an ORDER BY clause, then we need to sort the results
  ** and send them to the callback one by one.
  */
-  if( pOrderBy ){
-    explainTempTable(pParse, "ORDER BY");
-    generateSortTail(pParse, p, v, pEList->nExpr, pDest);
+  if( sSort.pOrderBy ){
+    explainTempTable(pParse, sSort.nOBSat>0 ? "RIGHT PART OF ORDER BY":"ORDER BY");
+    generateSortTail(pParse, p, &sSort, pEList->nExpr, pDest);
  }

  /* Jump here to skip this query
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1958,7 +1958,6 @@ struct Expr {
 */
 struct ExprList {
  int nExpr;             /* Number of expressions on the list */
-  int iECursor;          /* VDBE Cursor associated with this ExprList */
  struct ExprList_item { /* For each expression in the list */
    Expr *pExpr;            /* The list of expressions */
    char *zName;            /* Token associated with this expression */
@@ -2182,7 +2181,7 @@ struct Select {
  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
  u16 selFlags;          /* Various SF_* values */
  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
-  int addrOpenEphm[3];   /* OP_OpenEphem opcodes related to this select */
+  int addrOpenEphm[2];   /* OP_OpenEphem opcodes related to this select */
  u64 nSelectRow;        /* Estimated number of result rows */
  SrcList *pSrc;         /* The FROM clause */
  Expr *pWhere;          /* The WHERE clause */
@@ -2206,9 +2205,9 @@ struct Select {
 #define SF_UsesEphemeral   0x0008  /* Uses the OpenEphemeral opcode */
 #define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
 #define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
-#define SF_UseSorter       0x0040  /* Sort using a sorter */
+                    /*     0x0040  NOT USED */
 #define SF_Values          0x0080  /* Synthesized from VALUES clause */
-#define SF_Materialize     0x0100  /* NOT USED */
+                    /*     0x0100  NOT USED */
 #define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
 #define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */
 #define SF_Recursive       0x0800  /* The recursive part of a recursive CTE */
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -1080,10 +1080,11 @@ case OP_Variable: {            /* out2-prerelease */
 /* Opcode: Move P1 P2 P3 * *
 ** Synopsis:  r[P2@P3]=r[P1@P3]
 **
-** Move the values in register P1..P1+P3 over into
-** registers P2..P2+P3.  Registers P1..P1+P3 are
+** Move the P3 values in register P1..P1+P3-1 over into
+** registers P2..P2+P3-1.  Registers P1..P1+P3-1 are
 ** left holding a NULL.  It is an error for register ranges
-** P1..P1+P3 and P2..P2+P3 to overlap.
+** P1..P1+P3-1 and P2..P2+P3-1 to overlap.  It is an error
+** for P3 to be less than 1.
 */
 case OP_Move: {
  char *zMalloc;   /* Holding variable for allocated memory */
@@ -1094,7 +1095,7 @@ case OP_Move: {
  n = pOp->p3;
  p1 = pOp->p1;
  p2 = pOp->p2;
-  assert( n>=0 && p1>0 && p2>0 );
+  assert( n>0 && p1>0 && p2>0 );
  assert( p1+n<=p2 || p2+n<=p1 );

  pIn1 = &aMem[p1];
@@ -1118,7 +1119,7 @@ case OP_Move: {
    REGISTER_TRACE(p2++, pOut);
    pIn1++;
    pOut++;
-  }while( n-- );
+  }while( --n );
  break;
 }

@@ -1995,6 +1996,7 @@ case OP_Permutation: {
 }

 /* Opcode: Compare P1 P2 P3 P4 P5
+** Synopsis: r[P1@P3] <-> r[P2@P3]
 **
 ** Compare two vectors of registers in reg(P1)..reg(P1+P3-1) (call this
 ** vector "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
@@ -3330,6 +3332,7 @@ case OP_OpenEphemeral: {
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
+  pCx->isEphemeral = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
@@ -3820,7 +3823,7 @@ case OP_NotExists: {        /* jump, in3 */
 }

 /* Opcode: Sequence P1 P2 * * *
-** Synopsis: r[P2]=rowid
+** Synopsis: r[P2]=cursor[P1].ctr++
 **
 ** Find the next available sequence number for cursor P1.
 ** Write the sequence number into register P2.
@@ -4869,6 +4872,29 @@ case OP_Clear: {
  break;
 }

+/* Opcode: ResetSorter P1 * * * *
+**
+** Delete all contents from the ephemeral table or sorter
+** that is open on cursor P1.
+**
+** This opcode only works for cursors used for sorting and
+** opened with OP_OpenEphemeral or OP_SorterOpen.
+*/
+case OP_ResetSorter: {
+  VdbeCursor *pC;
+ 
+  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  if( pC->pSorter ){
+    sqlite3VdbeSorterReset(db, pC->pSorter);
+  }else{
+    assert( pC->isEphemeral );
+    rc = sqlite3BtreeClearTableOfCursor(pC->pCursor);
+  }
+  break;
+}
+
 /* Opcode: CreateTable P1 P2 * * *
 ** Synopsis: r[P2]=root iDb=P1
 **
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -72,6 +72,7 @@ struct VdbeCursor {
  u8 nullRow;           /* True if pointing to a row with no data */
  u8 rowidIsValid;      /* True if lastRowid is valid */
  u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
+  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isTable:1;       /* True if a table requiring integer keys */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
@@ -437,6 +438,7 @@ int sqlite3VdbeFrameRestore(VdbeFrame *);
 int sqlite3VdbeTransferError(Vdbe *p);

 int sqlite3VdbeSorterInit(sqlite3 *, VdbeCursor *);
+void sqlite3VdbeSorterReset(sqlite3 *, VdbeSorter *);
 void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
 int sqlite3VdbeSorterRowkey(const VdbeCursor *, Mem *);
 int sqlite3VdbeSorterNext(sqlite3 *, const VdbeCursor *, int *);
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -783,7 +783,9 @@ void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
    addr = p->nOp - 1;
  }
  pOp = &p->aOp[addr];
-  assert( pOp->p4type==P4_NOTUSED || pOp->p4type==P4_INT32 );
+  assert( pOp->p4type==P4_NOTUSED
+       || pOp->p4type==P4_INT32
+       || pOp->p4type==P4_KEYINFO );
  freeP4(db, pOp->p4type, pOp->p4.p);
  pOp->p4.p = 0;
  if( n==P4_INT32 ){
--- a/src/vdbesort.c
+++ b/src/vdbesort.c
@@ -504,23 +504,40 @@ static void vdbeSorterRecordFree(sqlite3 *db, SorterRecord *pRecord){
  }
 }

+/*
+** Reset a sorting cursor back to its original empty state.
+*/
+void sqlite3VdbeSorterReset(sqlite3 *db, VdbeSorter *pSorter){
+  if( pSorter->aIter ){
+    int i;
+    for(i=0; i<pSorter->nTree; i++){
+      vdbeSorterIterZero(db, &pSorter->aIter[i]);
+    }
+    sqlite3DbFree(db, pSorter->aIter);
+    pSorter->aIter = 0;
+  }
+  if( pSorter->pTemp1 ){
+    sqlite3OsCloseFree(pSorter->pTemp1);
+    pSorter->pTemp1 = 0;
+  }
+  vdbeSorterRecordFree(db, pSorter->pRecord);
+  pSorter->pRecord = 0;
+  pSorter->iWriteOff = 0;
+  pSorter->iReadOff = 0;
+  pSorter->nInMemory = 0;
+  pSorter->nTree = 0;
+  pSorter->nPMA = 0;
+  pSorter->aTree = 0;
+}
+
+
 /*
 ** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
 */
 void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
  VdbeSorter *pSorter = pCsr->pSorter;
  if( pSorter ){
-    if( pSorter->aIter ){
-      int i;
-      for(i=0; i<pSorter->nTree; i++){
-        vdbeSorterIterZero(db, &pSorter->aIter[i]);
-      }
-      sqlite3DbFree(db, pSorter->aIter);
-    }
-    if( pSorter->pTemp1 ){
-      sqlite3OsCloseFree(pSorter->pTemp1);
-    }
-    vdbeSorterRecordFree(db, pSorter->pRecord);
+    sqlite3VdbeSorterReset(db, pSorter);
    sqlite3DbFree(db, pSorter->pUnpacked);
    sqlite3DbFree(db, pSorter);
    pCsr->pSorter = 0;
--- a/src/where.c
+++ b/src/where.c
@@ -39,7 +39,7 @@ int sqlite3WhereIsDistinct(WhereInfo *pWInfo){
 ** Return FALSE if the output needs to be sorted.
 */
 int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
-  return pWInfo->bOBSat!=0;
+  return pWInfo->nOBSat;
 }

 /*
@@ -3037,8 +3037,11 @@ static Bitmask codeOneLoopStart(
    ** the first one after the nEq equality constraints in the index,
    ** this requires some special handling.
    */
+    assert( pWInfo->pOrderBy==0
+         || pWInfo->pOrderBy->nExpr==1
+         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
-     && (pWInfo->bOBSat!=0)
+     && pWInfo->nOBSat>0
     && (pIdx->nKeyCol>nEq)
    ){
      assert( pLoop->u.btree.nSkip==0 );
@@ -4508,8 +4511,8 @@ static int whereLoopAddVirtual(
      pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
      pIdxInfo->needToFreeIdxStr = 0;
      pNew->u.vtab.idxStr = pIdxInfo->idxStr;
-      pNew->u.vtab.isOrdered = (u8)((pIdxInfo->nOrderBy!=0)
-                                     && pIdxInfo->orderByConsumed);
+      pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
+                                      pIdxInfo->nOrderBy : 0);
      pNew->rSetup = 0;
      pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
      pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);
@@ -4670,11 +4673,11 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
 /*
 ** Examine a WherePath (with the addition of the extra WhereLoop of the 5th
 ** parameters) to see if it outputs rows in the requested ORDER BY
-** (or GROUP BY) without requiring a separate sort operation.  Return:
+** (or GROUP BY) without requiring a separate sort operation.  Return N:
 ** 
-**    0:  ORDER BY is not satisfied.  Sorting required
-**    1:  ORDER BY is satisfied.      Omit sorting
-**   -1:  Unknown at this time
+**   N>0:   N terms of the ORDER BY clause are satisfied
+**   N==0:  No terms of the ORDER BY clause are satisfied
+**   N<0:   Unknown yet how many terms of ORDER BY might be satisfied.   
 **
 ** Note that processing for WHERE_GROUPBY and WHERE_DISTINCTBY is not as
 ** strict.  With GROUP BY and DISTINCT the only requirement is that
@@ -4684,7 +4687,7 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
 ** the pOrderBy terms can be matched in any order.  With ORDER BY, the 
 ** pOrderBy terms must be matched in strict left-to-right order.
 */
-static int wherePathSatisfiesOrderBy(
+static i8 wherePathSatisfiesOrderBy(
  WhereInfo *pWInfo,    /* The WHERE clause */
  ExprList *pOrderBy,   /* ORDER BY or GROUP BY or DISTINCT clause to check */
  WherePath *pPath,     /* The WherePath to check */
@@ -4917,8 +4920,14 @@ static int wherePathSatisfiesOrderBy(
      }
    }
  } /* End the loop over all WhereLoops from outer-most down to inner-most */
-  if( obSat==obDone ) return 1;
-  if( !isOrderDistinct ) return 0;
+  if( obSat==obDone ) return nOrderBy;
+  if( !isOrderDistinct ){
+    for(i=nOrderBy-1; i>0; i--){
+      Bitmask m = MASKBIT(i) - 1;
+      if( (obSat&m)==m ) return i;
+    }
+    return 0;
+  }
  return -1;
 }

@@ -4955,11 +4964,11 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
  int iLoop;                /* Loop counter over the terms of the join */
  int ii, jj;               /* Loop counters */
  int mxI = 0;              /* Index of next entry to replace */
+  int nOrderBy;             /* Number of ORDER BY clause terms */
  LogEst rCost;             /* Cost of a path */
  LogEst nOut;              /* Number of outputs */
  LogEst mxCost = 0;        /* Maximum cost of a set of paths */
  LogEst mxOut = 0;         /* Maximum nOut value on the set of paths */
-  LogEst rSortCost;         /* Cost to do a sort */
  int nTo, nFrom;           /* Number of valid entries in aTo[] and aFrom[] */
  WherePath *aFrom;         /* All nFrom paths at the previous level */
  WherePath *aTo;           /* The nTo best paths at the current level */
@@ -5001,16 +5010,12 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){

  /* Precompute the cost of sorting the final result set, if the caller
  ** to sqlite3WhereBegin() was concerned about sorting */
-  rSortCost = 0;
  if( pWInfo->pOrderBy==0 || nRowEst==0 ){
-    aFrom[0].isOrderedValid = 1;
+    aFrom[0].isOrdered = 0;
+    nOrderBy = 0;
  }else{
-    /* TUNING: Estimated cost of sorting is 48*N*log2(N) where N is the
-    ** number of output rows. The 48 is the expected size of a row to sort. 
-    ** FIXME:  compute a better estimate of the 48 multiplier based on the
-    ** result set expressions. */
-    rSortCost = nRowEst + estLog(nRowEst);
-    WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
+    aFrom[0].isOrdered = -1;
+    nOrderBy = pWInfo->pOrderBy->nExpr;
  }

  /* Compute successively longer WherePaths using the previous generation
@@ -5022,8 +5027,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
      for(pWLoop=pWInfo->pLoops; pWLoop; pWLoop=pWLoop->pNextLoop){
        Bitmask maskNew;
        Bitmask revMask = 0;
-        u8 isOrderedValid = pFrom->isOrderedValid;
-        u8 isOrdered = pFrom->isOrdered;
+        i8 isOrdered = pFrom->isOrdered;
        if( (pWLoop->prereq & ~pFrom->maskLoop)!=0 ) continue;
        if( (pWLoop->maskSelf & pFrom->maskLoop)!=0 ) continue;
        /* At this point, pWLoop is a candidate to be the next loop. 
@@ -5032,21 +5036,27 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
        rCost = sqlite3LogEstAdd(rCost, pFrom->rCost);
        nOut = pFrom->nRow + pWLoop->nOut;
        maskNew = pFrom->maskLoop | pWLoop->maskSelf;
-        if( !isOrderedValid ){
-          switch( wherePathSatisfiesOrderBy(pWInfo,
+        if( isOrdered<0 ){
+          isOrdered = wherePathSatisfiesOrderBy(pWInfo,
                       pWInfo->pOrderBy, pFrom, pWInfo->wctrlFlags,
-                       iLoop, pWLoop, &revMask) ){
-            case 1:  /* Yes.  pFrom+pWLoop does satisfy the ORDER BY clause */
-              isOrdered = 1;
-              isOrderedValid = 1;
-              break;
-            case 0:  /* No.  pFrom+pWLoop will require a separate sort */
-              isOrdered = 0;
-              isOrderedValid = 1;
-              rCost = sqlite3LogEstAdd(rCost, rSortCost);
-              break;
-            default: /* Cannot tell yet.  Try again on the next iteration */
-              break;
+                       iLoop, pWLoop, &revMask);
+          if( isOrdered>=0 && isOrdered<nOrderBy ){
+            /* TUNING: Estimated cost of sorting cost as roughly N*log(N).
+            ** If some but not all of the columns are in sorted order, then
+            ** scale down the log(N) term. */
+            LogEst rScale = sqlite3LogEst((nOrderBy-isOrdered)*100/nOrderBy);
+            LogEst rSortCost = nRowEst + estLog(nRowEst) + rScale - 66;
+            /* TUNING: The cost of implementing DISTINCT using a B-TREE is
+            ** also N*log(N) but it has a larger constant of proportionality.
+            ** Multiply by 3.0. */
+            if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
+              rSortCost += 16;
+            }
+            WHERETRACE(0x002,
+               ("---- sort cost=%-3d (%d/%d) increases cost %3d to %-3d\n",
+                rSortCost, (nOrderBy-isOrdered), nOrderBy, rCost,
+                sqlite3LogEstAdd(rCost,rSortCost)));
+            rCost = sqlite3LogEstAdd(rCost, rSortCost);
          }
        }else{
          revMask = pFrom->revLoop;
@@ -5054,7 +5064,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
        /* Check to see if pWLoop should be added to the mxChoice best so far */
        for(jj=0, pTo=aTo; jj<nTo; jj++, pTo++){
          if( pTo->maskLoop==maskNew
-           && pTo->isOrderedValid==isOrderedValid
+           && ((pTo->isOrdered^isOrdered)&80)==0
           && ((pTo->rCost<=rCost && pTo->nRow<=nOut) ||
                (pTo->rCost>=rCost && pTo->nRow>=nOut))
          ){
@@ -5068,7 +5078,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
            if( sqlite3WhereTrace&0x4 ){
              sqlite3DebugPrintf("Skip   %s cost=%-3d,%3d order=%c\n",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
-                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
+                  isOrdered>=0 ? isOrdered+'0' : '?');
            }
 #endif
            continue;
@@ -5086,7 +5096,7 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
          if( sqlite3WhereTrace&0x4 ){
            sqlite3DebugPrintf("New    %s cost=%-3d,%3d order=%c\n",
                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
-                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
+                isOrdered>=0 ? isOrdered+'0' : '?');
          }
 #endif
        }else{
@@ -5096,10 +5106,10 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
              sqlite3DebugPrintf(
                  "Skip   %s cost=%-3d,%3d order=%c",
                  wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
-                  isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
+                  isOrdered>=0 ? isOrdered+'0' : '?');
              sqlite3DebugPrintf("   vs %s cost=%-3d,%d order=%c\n",
                  wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
-                  pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
+                  pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
            }
 #endif
            testcase( pTo->rCost==rCost );
@@ -5112,10 +5122,10 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
            sqlite3DebugPrintf(
                "Update %s cost=%-3d,%3d order=%c",
                wherePathName(pFrom, iLoop, pWLoop), rCost, nOut,
-                isOrderedValid ? (isOrdered ? 'Y' : 'N') : '?');
+                isOrdered>=0 ? isOrdered+'0' : '?');
            sqlite3DebugPrintf("  was %s cost=%-3d,%3d order=%c\n",
                wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
-                pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
+                pTo->isOrdered>=0 ? pTo->isOrdered+'0' : '?');
          }
 #endif
        }
@@ -5124,7 +5134,6 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
        pTo->revLoop = revMask;
        pTo->nRow = nOut;
        pTo->rCost = rCost;
-        pTo->isOrderedValid = isOrderedValid;
        pTo->isOrdered = isOrdered;
        memcpy(pTo->aLoop, pFrom->aLoop, sizeof(WhereLoop*)*iLoop);
        pTo->aLoop[iLoop] = pWLoop;
@@ -5149,8 +5158,8 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
      for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
        sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
           wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
-           pTo->isOrderedValid ? (pTo->isOrdered ? 'Y' : 'N') : '?');
-        if( pTo->isOrderedValid && pTo->isOrdered ){
+           pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
+        if( pTo->isOrdered>0 ){
          sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);
        }else{
          sqlite3DebugPrintf("\n");
@@ -5193,13 +5202,18 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
    Bitmask notUsed;
    int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pResultSet, pFrom,
                 WHERE_DISTINCTBY, nLoop-1, pFrom->aLoop[nLoop-1], &notUsed);
-    if( rc==1 ) pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
-  }
-  if( pFrom->isOrdered ){
-    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
+    if( rc==pWInfo->pResultSet->nExpr ){
      pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
+    }
+  }
+  if( pWInfo->pOrderBy ){
+    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
+      if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
+        pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
+      }
    }else{
-      pWInfo->bOBSat = 1;
+      pWInfo->nOBSat = pFrom->isOrdered;
+      if( pWInfo->nOBSat<0 ) pWInfo->nOBSat = 0;
      pWInfo->revMask = pFrom->revLoop;
    }
  }
@@ -5284,7 +5298,7 @@ static int whereShortCut(WhereLoopBuilder *pBuilder){
    pLoop->maskSelf = getMask(&pWInfo->sMaskSet, iCur);
    pWInfo->a[0].iTabCur = iCur;
    pWInfo->nRowOut = 1;
-    if( pWInfo->pOrderBy ) pWInfo->bOBSat =  1;
+    if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
    if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }
@@ -5388,7 +5402,7 @@ WhereInfo *sqlite3WhereBegin(
  Parse *pParse,        /* The parser context */
  SrcList *pTabList,    /* FROM clause: A list of all tables to be scanned */
  Expr *pWhere,         /* The WHERE clause */
-  ExprList *pOrderBy,   /* An ORDER BY clause, or NULL */
+  ExprList *pOrderBy,   /* An ORDER BY (or GROUP BY) clause, or NULL */
  ExprList *pResultSet, /* Result set of the query */
  u16 wctrlFlags,       /* One of the WHERE_* flags defined in sqliteInt.h */
  int iIdxCur           /* If WHERE_ONETABLE_ONLY is set, index cursor number */
@@ -5410,6 +5424,10 @@ WhereInfo *sqlite3WhereBegin(
  /* Variable initialization */
  db = pParse->db;
  memset(&sWLB, 0, sizeof(sWLB));
+
+  /* An ORDER/GROUP BY clause of more than 63 terms cannot be optimized */
+  testcase( pOrderBy && pOrderBy->nExpr==BMS-1 );
+  if( pOrderBy && pOrderBy->nExpr>=BMS ) pOrderBy = 0;
  sWLB.pOrderBy = pOrderBy;

  /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
@@ -5488,7 +5506,7 @@ WhereInfo *sqlite3WhereBegin(
  /* Special case: No FROM clause
  */
  if( nTabList==0 ){
-    if( pOrderBy ) pWInfo->bOBSat = 1;
+    if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
    if( wctrlFlags & WHERE_WANT_DISTINCT ){
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }
@@ -5599,8 +5617,8 @@ WhereInfo *sqlite3WhereBegin(
  if( sqlite3WhereTrace ){
    int ii;
    sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
-    if( pWInfo->bOBSat ){
-      sqlite3DebugPrintf(" ORDERBY=0x%llx", pWInfo->revMask);
+    if( pWInfo->nOBSat>0 ){
+      sqlite3DebugPrintf(" ORDERBY=%d,0x%llx", pWInfo->nOBSat, pWInfo->revMask);
    }
    switch( pWInfo->eDistinct ){
      case WHERE_DISTINCT_UNIQUE: {
--- a/src/whereInt.h
+++ b/src/whereInt.h
@@ -121,7 +121,7 @@ struct WhereLoop {
    struct {               /* Information for virtual tables */
      int idxNum;            /* Index number */
      u8 needFree;           /* True if sqlite3_free(idxStr) is needed */
-      u8 isOrdered;          /* True if satisfies ORDER BY */
+      i8 isOrdered;          /* True if satisfies ORDER BY */
      u16 omitMask;          /* Terms that may be omitted */
      char *idxStr;          /* Index identifier string */
    } vtab;
@@ -183,8 +183,7 @@ struct WherePath {
  Bitmask revLoop;      /* aLoop[]s that should be reversed for ORDER BY */
  LogEst nRow;          /* Estimated number of rows generated by this path */
  LogEst rCost;         /* Total cost of this path */
-  u8 isOrdered;         /* True if this path satisfies ORDER BY */
-  u8 isOrderedValid;    /* True if the isOrdered field is valid */
+  i8 isOrdered;         /* No. of ORDER BY terms satisfied. -1 for unknown */
  WhereLoop **aLoop;    /* Array of WhereLoop objects implementing this path */
 };

@@ -398,7 +397,7 @@ struct WhereInfo {
  Bitmask revMask;          /* Mask of ORDER BY terms that need reversing */
  LogEst nRowOut;           /* Estimated number of output rows */
  u16 wctrlFlags;           /* Flags originally passed to sqlite3WhereBegin() */
-  u8 bOBSat;                /* ORDER BY satisfied by indices */
+  i8 nOBSat;                /* Number of ORDER BY terms satisfied by indices */
  u8 okOnePass;             /* Ok to use one-pass algorithm for UPDATE/DELETE */
  u8 untestedTerms;         /* Not all WHERE terms resolved by outer loop */
  u8 eDistinct;             /* One of the WHERE_DISTINCT_* values below */
--- a/test/distinct.test
+++ b/test/distinct.test
@@ -162,7 +162,7 @@ do_execsql_test 2.0 {
 foreach {tn sql temptables res} {
  1   "a, b FROM t1"                                       {}      {A B a b}
  2   "b, a FROM t1"                                       {}      {B A b a}
-  3   "a, b, c FROM t1"                                    {hash}  {a b c A B C}
+  3   "a, b, c FROM t1"                                    {hash}  {A B C a b c}
  4   "a, b, c FROM t1 ORDER BY a, b, c"                   {btree} {A B C a b c}
  5   "b FROM t1 WHERE a = 'a'"                            {}      {b}
  6   "b FROM t1 ORDER BY +b COLLATE binary"          {btree hash} {B b}
--- a/test/orderby5.test
+++ b/test/orderby5.test
@@ -64,10 +64,28 @@ do_execsql_test 1.7 {
  EXPLAIN QUERY PLAN
  SELECT DISTINCT c, b, a FROM t1 WHERE +a=0;
 } {/B-TREE/}
-do_execsql_test 2.1 {
+
+# In some cases, it is faster to do repeated index lookups than it is to
+# sort.  But in other cases, it is faster to sort than to do repeated index
+# lookups.
+#
+do_execsql_test 2.1a {
+  CREATE TABLE t2(a,b,c);
+  CREATE INDEX t2bc ON t2(b,c);
+  ANALYZE;
+  INSERT INTO sqlite_stat1 VALUES('t1','t1bc','1000000 10 9');
+  INSERT INTO sqlite_stat1 VALUES('t2','t2bc','100 10 5');
+  ANALYZE sqlite_master;
+
+  EXPLAIN QUERY PLAN
+  SELECT * FROM t2 WHERE a=0 ORDER BY a, b, c;
+} {~/B-TREE/}
+do_execsql_test 2.1b {
  EXPLAIN QUERY PLAN
  SELECT * FROM t1 WHERE a=0 ORDER BY a, b, c;
-} {~/B-TREE/}
+} {/B-TREE/}
+
+
 do_execsql_test 2.2 {
  EXPLAIN QUERY PLAN
  SELECT * FROM t1 WHERE +a=0 ORDER BY a, b, c;
--- a/test/orderby6.test
+++ b/test/orderby6.test
@@ -0,0 +1,183 @@
+# 2014-03-21
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is testing that the block-sort optimization.
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set ::testprefix orderby6
+
+# Run all tests twice.  Once with a normal table and a second time
+# with a WITHOUT ROWID table
+#
+foreach {tn rowidclause} {1 {} 2 {WITHOUT ROWID}} {
+
+  # Construct a table with 1000 rows and a split primary key
+  #
+  reset_db
+  do_test $tn.1 {
+    db eval "CREATE TABLE t1(a,b,c,PRIMARY KEY(b,c)) $rowidclause;"
+    db eval {
+      WITH RECURSIVE
+       cnt(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM cnt WHERE x<1000)
+     INSERT INTO t1 SELECT x, x%40, x/40 FROM cnt;
+    }
+  } {}
+
+  # Run various ORDER BY queries that can benefit from block-sort.
+  # Compare the output to the same output using a full-sort enforced
+  # by adding + to each term of the ORDER BY clause.
+  #
+  do_execsql_test $tn.2 {
+    SELECT b,a,c FROM t1 ORDER BY b,a,c;
+  } [db eval {SELECT b,a,c FROM t1 ORDER BY +b,+a,+c}]
+  do_execsql_test $tn.3 {
+    SELECT b,a,c FROM t1 ORDER BY b,c DESC,a;
+  } [db eval {SELECT b,a,c FROM t1 ORDER BY +b,+c DESC,+a}]
+  do_execsql_test $tn.4 {
+    SELECT b,a,c FROM t1 ORDER BY b DESC,c,a;
+  } [db eval {SELECT b,a,c FROM t1 ORDER BY +b DESC,+c,+a}]
+  do_execsql_test $tn.5 {
+    SELECT b,a,c FROM t1 ORDER BY b DESC,a,c;
+  } [db eval {SELECT b,a,c FROM t1 ORDER BY +b DESC,+a,+c}]
+
+  # LIMIT and OFFSET clauses on block-sort queries.
+  #
+  do_execsql_test $tn.11 {
+    SELECT a FROM t1 ORDER BY b, a LIMIT 10 OFFSET 20;
+  } {840 880 920 960 1000 1 41 81 121 161}
+  do_execsql_test $tn.11x {
+    SELECT a FROM t1 ORDER BY +b, a LIMIT 10 OFFSET 20;
+  } {840 880 920 960 1000 1 41 81 121 161}
+
+  do_execsql_test $tn.12 {
+    SELECT a FROM t1 ORDER BY b DESC, a LIMIT 10 OFFSET 20;
+  } {839 879 919 959 999 38 78 118 158 198}
+  do_execsql_test $tn.12 {
+    SELECT a FROM t1 ORDER BY +b DESC, a LIMIT 10 OFFSET 20;
+  } {839 879 919 959 999 38 78 118 158 198}
+
+  do_execsql_test $tn.13 {
+    SELECT a FROM t1 ORDER BY b, a DESC LIMIT 10 OFFSET 45;
+  } {161 121 81 41 1 962 922 882 842 802}
+  do_execsql_test $tn.13x {
+    SELECT a FROM t1 ORDER BY +b, a DESC LIMIT 10 OFFSET 45;
+  } {161 121 81 41 1 962 922 882 842 802}
+
+  do_execsql_test $tn.14 {
+    SELECT a FROM t1 ORDER BY b DESC, a LIMIT 10 OFFSET 45;
+  } {838 878 918 958 998 37 77 117 157 197}
+  do_execsql_test $tn.14x {
+    SELECT a FROM t1 ORDER BY +b DESC, a LIMIT 10 OFFSET 45;
+  } {838 878 918 958 998 37 77 117 157 197}
+
+  # Many test cases where the LIMIT+OFFSET window is in various
+  # alignments with block-sort boundaries.
+  #
+  foreach {tx limit offset orderby} {
+     1  10 24 {+b,+a}
+     2  10 25 {+b,+a}
+     3  10 26 {+b,+a}
+     4  10 39 {+b,+a}
+     5  10 40 {+b,+a}
+     6  10 41 {+b,+a}
+     7  27 24 {+b,+a}
+     8  27 49 {+b,+a}
+     11 10 24 {+b DESC,+a}
+     12 10 25 {+b DESC,+a}
+     13 10 26 {+b DESC,+a}
+     14 10 39 {+b DESC,+a}
+     15 10 40 {+b DESC,+a}
+     16 10 41 {+b DESC,+a}
+     17 27 24 {+b DESC,+a}
+     18 27 49 {+b DESC,+a}
+     21 10 24 {+b,+a DESC}
+     22 10 25 {+b,+a DESC}
+     23 10 26 {+b,+a DESC}
+     24 10 39 {+b,+a DESC}
+     25 10 40 {+b,+a DESC}
+     26 10 41 {+b,+a DESC}
+     27 27 24 {+b,+a DESC}
+     28 27 49 {+b,+a DESC}
+     31 10 24 {+b DESC,+a DESC}
+     32 10 25 {+b DESC,+a DESC}
+     33 10 26 {+b DESC,+a DESC}
+     34 10 39 {+b DESC,+a DESC}
+     35 10 40 {+b DESC,+a DESC}
+     36 10 41 {+b DESC,+a DESC}
+     37 27 24 {+b DESC,+a DESC}
+     38 27 49 {+b DESC,+a DESC}
+  } {
+    set sql1 "SELECT a FROM t1 ORDER BY $orderby LIMIT $limit OFFSET $offset;"
+    set sql2 [string map {+ {}} $sql1]
+    # puts $sql2\n$sql1\n[db eval $sql2]
+    do_test $tn.21.$tx {db eval $::sql2} [db eval $sql1]
+  }
+
+  ########################################################################
+  # A second test table, t2, has many columns open to sorting.
+  do_test $tn.31 {
+    db eval "CREATE TABLE t2(a,b,c,d,e,f,PRIMARY KEY(b,c,d,e,f)) $rowidclause;"
+    db eval {
+      WITH RECURSIVE
+       cnt(x) AS (VALUES(0) UNION ALL SELECT x+1 FROM cnt WHERE x<242)
+     INSERT INTO t2 SELECT x,  x%3, (x/3)%3, (x/9)%3, (x/27)%3, (x/81)%3
+                      FROM cnt;
+    }
+  } {}
+
+  do_execsql_test $tn.32 {
+    SELECT a FROM t2 ORDER BY b,c,d,e,f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f;}]
+  do_execsql_test $tn.33 {
+    SELECT a FROM t2 ORDER BY b,c,d,e,+f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f;}]
+  do_execsql_test $tn.34 {
+    SELECT a FROM t2 ORDER BY b,c,d,+e,+f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f;}]
+  do_execsql_test $tn.35 {
+    SELECT a FROM t2 ORDER BY b,c,+d,+e,+f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f;}]
+  do_execsql_test $tn.36 {
+    SELECT a FROM t2 ORDER BY b,+c,+d,+e,+f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f;}]
+
+  do_execsql_test $tn.37 {
+    SELECT a FROM t2 ORDER BY b,c,d,e,f DESC;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f DESC;}]
+  do_execsql_test $tn.38 {
+    SELECT a FROM t2 ORDER BY b,c,d,e DESC,f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e DESC,+f;}]
+  do_execsql_test $tn.39 {
+    SELECT a FROM t2 ORDER BY b,c,d DESC,e,f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d DESC,+e,+f;}]
+  do_execsql_test $tn.40 {
+    SELECT a FROM t2 ORDER BY b,c DESC,d,e,f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c DESC,+d,+e,+f;}]
+  do_execsql_test $tn.41 {
+    SELECT a FROM t2 ORDER BY b DESC,c,d,e,f;
+  } [db eval {SELECT a FROM t2 ORDER BY +b DESC,+c,+d,+e,+f;}]
+
+  do_execsql_test $tn.42 {
+    SELECT a FROM t2 ORDER BY b DESC,c DESC,d,e,f LIMIT 31;
+  } [db eval {SELECT a FROM t2 ORDER BY +b DESC,+c DESC,+d,+e,+f LIMIT 31}]
+  do_execsql_test $tn.43 {
+    SELECT a FROM t2 ORDER BY b,c,d,e,f DESC LIMIT 8 OFFSET 7;
+  } [db eval {SELECT a FROM t2 ORDER BY +b,+c,+d,+e,+f DESC LIMIT 8 OFFSET 7}]
+
+
+}
+
+
+
+finish_test
--- a/test/whereG.test
+++ b/test/whereG.test
@@ -95,7 +95,7 @@ do_eqp_test whereG-1.5 {
   WHERE cname LIKE '%bach%'
     AND composer.cid=track.cid
     AND album.aid=track.aid;
-} {/.*track.*composer.*album.*/}
+} {/.*track.*(composer.*album|album.*composer).*/}
 do_execsql_test whereG-1.6 {
  SELECT DISTINCT aname
    FROM album, composer, track
@@ -110,7 +110,7 @@ do_eqp_test whereG-1.7 {
   WHERE cname LIKE '%bach%'
     AND unlikely(composer.cid=track.cid)
     AND unlikely(album.aid=track.aid);
-} {/.*track.*composer.*album.*/}
+} {/.*track.*(composer.*album|album.*composer).*/}
 do_execsql_test whereG-1.8 {
  SELECT DISTINCT aname
    FROM album, composer, track