Micro-optimizations in sqlite3BtreeNext() and sqlite3BtreePrevious().

FossilOrigin-Name: 839c7996eecd5480152c514555b9aa1121a69ce0

manifest

@@ -1,5 +1,5 @@
-C Fix\sharmless\scompiler\swarnings\sfor\sMSVC.
+C Micro-optimizations\sin\ssqlite3BtreeNext()\sand\ssqlite3BtreePrevious().
-D 2014-09-01T01:16:49.641
+D 2014-09-01T13:29:32.250
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5eb79e334a5de69c87740edd56af6527dd219308
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -168,7 +168,7 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c a31809c65623cc41849b94d368917f8bb66e6a7e
 F src/bitvec.c 19a4ba637bd85f8f63fc8c9bae5ade9fb05ec1cb
 F src/btmutex.c ec9d3f1295dafeb278c3830211cc5584132468f4
-F src/btree.c 4737cb5bdb2eb8989cb292f6ff921f7ff45f0c46
+F src/btree.c 4d0427bab54229030fc5b8577d2e5ffdc8129030
 F src/btree.h a79aa6a71e7f1055f01052b7f821bd1c2dce95c8
 F src/btreeInt.h cf180d86b2e9e418f638d65baa425c4c69c0e0e3
 F src/build.c 058e3aadb1376521ff291735237edf4c10f438fb
@@ -1188,7 +1188,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P f61db04be4d7fb21b7f721647c37c45e283ffbea
+P 3ef3246120d72dffe469733bb21667a548af0a44
-R fb90b1156ce26645b130e94c9528a286
+R 8a87472d819e62a6d7e88f3d5e77ba23
-U mistachkin
+U drh
-Z ab89ed2842a9e03f7299dfc1fb42f5cb
+Z 5b0c8a527e1dec5d8cc1bbd203422489

manifest.uuid

@@ -1 +1 @@
-3ef3246120d72dffe469733bb21667a548af0a44
+839c7996eecd5480152c514555b9aa1121a69ce0

src/btree.c

@@ -4513,17 +4513,16 @@ static int moveToRightmost(BtCursor *pCur){
 
   assert( cursorHoldsMutex(pCur) );
   assert( pCur->eState==CURSOR_VALID );
-  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
+  while( !(pPage = pCur->apPage[pCur->iPage])->leaf ){
     pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
     pCur->aiIdx[pCur->iPage] = pPage->nCell;
     rc = moveToChild(pCur, pgno);
+    if( rc ) return rc;
   }
-  if( rc==SQLITE_OK ){
   pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
-    pCur->info.nSize = 0;
+  assert( pCur->info.nSize==0 );
-    pCur->curFlags &= ~BTCF_ValidNKey;
+  assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
-  }
+  return SQLITE_OK;
-  return rc;
 }
 
 /* Move the cursor to the first entry in the table.  Return SQLITE_OK
@@ -4843,6 +4842,12 @@ int sqlite3BtreeEof(BtCursor *pCur){
 ** was already pointing to the last entry in the database before
 ** this routine was called, then set *pRes=1.
 **
+** The main entry point is sqlite3BtreeNext().  That routine is optimized
+** for the common case of merely incrementing the cell counter BtCursor.aiIdx
+** to the next cell on the current page.  The (slower) btreeNext() helper
+** routine is called when it is necessary to move to a different page or
+** to restore the cursor.
+**
 ** The calling function will set *pRes to 0 or 1.  The initial *pRes value
 ** will be 1 if the cursor being stepped corresponds to an SQL index and
 ** if this routine could have been skipped if that SQL index had been
@@ -4852,20 +4857,18 @@ int sqlite3BtreeEof(BtCursor *pCur){
 ** SQLite btree implementation does not. (Note that the comdb2 btree
 ** implementation does use this hint, however.)
 */
-int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
+static SQLITE_NOINLINE int btreeNext(BtCursor *pCur, int *pRes){
   int rc;
   int idx;
   MemPage *pPage;
 
   assert( cursorHoldsMutex(pCur) );
-  assert( pRes!=0 );
-  assert( *pRes==0 || *pRes==1 );
   assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
+  assert( *pRes==0 );
   if( pCur->eState!=CURSOR_VALID ){
-    invalidateOverflowCache(pCur);
+    assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
     rc = restoreCursorPosition(pCur);
     if( rc!=SQLITE_OK ){
-      *pRes = 0;
       return rc;
     }
     if( CURSOR_INVALID==pCur->eState ){
@@ -4877,7 +4880,6 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
       pCur->eState = CURSOR_VALID;
       if( pCur->skipNext>0 ){
         pCur->skipNext = 0;
-        *pRes = 0;
         return SQLITE_OK;
       }
       pCur->skipNext = 0;
@@ -4895,18 +4897,11 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
   ** page into more than one b-tree structure. */
   testcase( idx>pPage->nCell );
 
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
   if( idx>=pPage->nCell ){
     if( !pPage->leaf ){
       rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
-      if( rc ){
+      if( rc ) return rc;
-        *pRes = 0;
+      return moveToLeftmost(pCur);
-        return rc;
-      }
-      rc = moveToLeftmost(pCur);
-      *pRes = 0;
-      return rc;
     }
     do{
       if( pCur->iPage==0 ){
@@ -4917,22 +4912,39 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
       moveToParent(pCur);
       pPage = pCur->apPage[pCur->iPage];
     }while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
-    *pRes = 0;
     if( pPage->intKey ){
-      rc = sqlite3BtreeNext(pCur, pRes);
+      return sqlite3BtreeNext(pCur, pRes);
     }else{
-      rc = SQLITE_OK;
-    }
-    return rc;
-  }
-  *pRes = 0;
-  if( pPage->leaf ){
       return SQLITE_OK;
     }
-  rc = moveToLeftmost(pCur);
+  }
-  return rc;
+  if( pPage->leaf ){
+    return SQLITE_OK;
+  }else{
+    return moveToLeftmost(pCur);
+  }
+}
+int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
+  MemPage *pPage;
+  assert( cursorHoldsMutex(pCur) );
+  assert( pRes!=0 );
+  assert( *pRes==0 || *pRes==1 );
+  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
+  pCur->info.nSize = 0;
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+  *pRes = 0;
+  if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur, pRes);
+  pPage = pCur->apPage[pCur->iPage];
+  if( (++pCur->aiIdx[pCur->iPage])>=pPage->nCell ){
+    pCur->aiIdx[pCur->iPage]--;
+    return btreeNext(pCur, pRes);
+  }
+  if( pPage->leaf ){
+    return SQLITE_OK;
+  }else{
+    return moveToLeftmost(pCur);
+  }
 }
-
 
 /*
 ** Step the cursor to the back to the previous entry in the database.  If
@@ -4940,6 +4952,12 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
 ** was already pointing to the first entry in the database before
 ** this routine was called, then set *pRes=1.
 **
+** The main entry point is sqlite3BtreePrevious().  That routine is optimized
+** for the common case of merely decrementing the cell counter BtCursor.aiIdx
+** to the previous cell on the current page.  The (slower) btreePrevious() helper
+** routine is called when it is necessary to move to a different page or
+** to restore the cursor.
+**
 ** The calling function will set *pRes to 0 or 1.  The initial *pRes value
 ** will be 1 if the cursor being stepped corresponds to an SQL index and
 ** if this routine could have been skipped if that SQL index had been
@@ -4949,23 +4967,22 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
 ** SQLite btree implementation does not. (Note that the comdb2 btree
 ** implementation does use this hint, however.)
 */
-int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
+static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur, int *pRes){
   int rc;
   MemPage *pPage;
 
   assert( cursorHoldsMutex(pCur) );
   assert( pRes!=0 );
-  assert( *pRes==0 || *pRes==1 );
+  assert( *pRes==0 );
   assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
-  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl);
+  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
+  assert( pCur->info.nSize==0 );
   if( pCur->eState!=CURSOR_VALID ){
-    if( ALWAYS(pCur->eState>=CURSOR_REQUIRESEEK) ){
+    assert( pCur->eState>=CURSOR_REQUIRESEEK );
     rc = btreeRestoreCursorPosition(pCur);
     if( rc!=SQLITE_OK ){
-        *pRes = 0;
       return rc;
     }
-    }
     if( CURSOR_INVALID==pCur->eState ){
       *pRes = 1;
       return SQLITE_OK;
@@ -4975,7 +4992,6 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
       pCur->eState = CURSOR_VALID;
       if( pCur->skipNext<0 ){
         pCur->skipNext = 0;
-        *pRes = 0;
         return SQLITE_OK;
       }
       pCur->skipNext = 0;
@@ -4987,10 +5003,7 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
   if( !pPage->leaf ){
     int idx = pCur->aiIdx[pCur->iPage];
     rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
-    if( rc ){
+    if( rc ) return rc;
-      *pRes = 0;
-      return rc;
-    }
     rc = moveToRightmost(pCur);
   }else{
     while( pCur->aiIdx[pCur->iPage]==0 ){
@@ -5001,8 +5014,8 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
       }
       moveToParent(pCur);
     }
-    pCur->info.nSize = 0;
+    assert( pCur->info.nSize==0 );
-    pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+    assert( (pCur->curFlags & (BTCF_ValidNKey|BTCF_ValidOvfl))==0 );
 
     pCur->aiIdx[pCur->iPage]--;
     pPage = pCur->apPage[pCur->iPage];
@@ -5012,9 +5025,25 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
       rc = SQLITE_OK;
     }
   }
-  *pRes = 0;
   return rc;
 }
+int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
+  assert( cursorHoldsMutex(pCur) );
+  assert( pRes!=0 );
+  assert( *pRes==0 || *pRes==1 );
+  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
+  *pRes = 0;
+  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
+  pCur->info.nSize = 0;
+  if( pCur->eState!=CURSOR_VALID
+   || pCur->aiIdx[pCur->iPage]==0
+   || pCur->apPage[pCur->iPage]->leaf==0
+  ){
+    return btreePrevious(pCur, pRes);
+  }
+  pCur->aiIdx[pCur->iPage]--;
+  return SQLITE_OK;
+}
 
 /*
 ** Allocate a new page from the database file.