Split the OP_Last opcode into OP_Last and OP_SeekEnd. Use OP_SeekEnd to

position a cursor prior to appending.  Ticket [cb91bf4290c211d].

FossilOrigin-Name: 3e02474c7bbe16891a7cfc8771cf72f64cd2c0692779037982d7d307512a4f23

3 files changed, 31 insertions, 25 deletions

diff --git a/src/build.c b/src/build.c
index 8eab3823c..37ed309b3 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2836,7 +2836,7 @@ static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
     addr2 = sqlite3VdbeCurrentAddr(v);
   }
   sqlite3VdbeAddOp3(v, OP_SorterData, iSorter, regRecord, iIdx);
-  sqlite3VdbeAddOp3(v, OP_Last, iIdx, 0, -1);
+  sqlite3VdbeAddOp1(v, OP_SeekEnd, iIdx);
   sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
   sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
   sqlite3ReleaseTempReg(pParse, regRecord);
diff --git a/src/insert.c b/src/insert.c
index d51e64b8f..f8e9095ea 100644
--- a/src/insert.c
+++ b/src/insert.c
@@ -2180,7 +2180,7 @@ static int xferOptimization(
     }
     sqlite3VdbeAddOp3(v, OP_RowData, iSrc, regData, 1);
     if( db->mDbFlags & DBFLAG_Vacuum ){
-      sqlite3VdbeAddOp3(v, OP_Last, iDest, 0, -1);
+      sqlite3VdbeAddOp1(v, OP_SeekEnd, iDest);
       insFlags = OPFLAG_NCHANGE|OPFLAG_LASTROWID|
                            OPFLAG_APPEND|OPFLAG_USESEEKRESULT;
     }else{
@@ -2217,7 +2217,7 @@ static int xferOptimization(
       ** collation sequence BINARY, then it can also be assumed that the
       ** index will be populated by inserting keys in strictly sorted 
       ** order. In this case, instead of seeking within the b-tree as part
-      ** of every OP_IdxInsert opcode, an OP_Last is added before the
+      ** of every OP_IdxInsert opcode, an OP_SeekEnd is added before the
       ** OP_IdxInsert to seek to the point within the b-tree where each key 
       ** should be inserted. This is faster.
       **
@@ -2232,7 +2232,7 @@ static int xferOptimization(
       }
       if( i==pSrcIdx->nColumn ){
         idxInsFlags = OPFLAG_USESEEKRESULT;
-        sqlite3VdbeAddOp3(v, OP_Last, iDest, 0, -1);
+        sqlite3VdbeAddOp1(v, OP_SeekEnd, iDest);
       }
     }
     if( !HasRowid(pSrc) && pDestIdx->idxType==2 ){
diff --git a/src/vdbe.c b/src/vdbe.c
index d9900f383..8ce5f0c5d 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -4776,7 +4776,17 @@ case OP_NullRow: {
   break;
 }
 
-/* Opcode: Last P1 P2 P3 * *
+/* Opcode: SeekEnd P1 * * * *
+**
+** Position cursor P1 at the end of the btree for the purpose of
+** appending a new entry onto the btree.
+**
+** It is assumed that the cursor is used only for appending and so
+** if the cursor is valid, then the cursor must already be pointing
+** at the end of the btree and so no changes are made to
+** the cursor.
+*/
+/* Opcode: Last P1 P2 * * *
 **
 ** The next use of the Rowid or Column or Prev instruction for P1 
 ** will refer to the last entry in the database table or index.
@@ -4787,14 +4797,8 @@ case OP_NullRow: {
 ** This opcode leaves the cursor configured to move in reverse order,
 ** from the end toward the beginning.  In other words, the cursor is
 ** configured to use Prev, not Next.
-**
-** If P3 is -1, then the cursor is positioned at the end of the btree
-** for the purpose of appending a new entry onto the btree.  In that
-** case P2 must be 0.  It is assumed that the cursor is used only for
-** appending and so if the cursor is valid, then the cursor must already
-** be pointing at the end of the btree and so no changes are made to
-** the cursor.
 */
+case OP_SeekEnd:
 case OP_Last: {        /* jump */
   VdbeCursor *pC;
   BtCursor *pCrsr;
@@ -4807,22 +4811,24 @@ case OP_Last: {        /* jump */
   pCrsr = pC->uc.pCursor;
   res = 0;
   assert( pCrsr!=0 );
-  pC->seekResult = pOp->p3;
 #ifdef SQLITE_DEBUG
-  pC->seekOp = OP_Last;
+  pC->seekOp = pOp->opcode;
 #endif
-  if( pOp->p3==0 || !sqlite3BtreeCursorIsValidNN(pCrsr) ){
-    rc = sqlite3BtreeLast(pCrsr, &res);
-    pC->nullRow = (u8)res;
-    pC->deferredMoveto = 0;
-    pC->cacheStatus = CACHE_STALE;
-    if( rc ) goto abort_due_to_error;
-    if( pOp->p2>0 ){
-      VdbeBranchTaken(res!=0,2);
-      if( res ) goto jump_to_p2;
-    }
-  }else{
+  if( pOp->opcode==OP_SeekEnd ){
     assert( pOp->p2==0 );
+    pC->seekResult = -1;
+    if( sqlite3BtreeCursorIsValidNN(pCrsr) ){
+      break;
+    }
+  }
+  rc = sqlite3BtreeLast(pCrsr, &res);
+  pC->nullRow = (u8)res;
+  pC->deferredMoveto = 0;
+  pC->cacheStatus = CACHE_STALE;
+  if( rc ) goto abort_due_to_error;
+  if( pOp->p2>0 ){
+    VdbeBranchTaken(res!=0,2);
+    if( res ) goto jump_to_p2;
   }
   break;
 }