Performance improvements in moveToChild() by shifting some work over

to getAndInitPage().  Net improvement is about 800K cycles at cost of 30 bytes.

FossilOrigin-Name: 1956a4ce8eca650d98a7f68fd2d82eb8a3d6069f

manifest

@@ -1,5 +1,5 @@
-C Manually\sinline\sthe\scall\sfrom\sgetAndInitPage()\sto\sbtreeGetPage()\sfor\sa\nsavings\sof\s2.5\smillion\scycles\sat\sa\scost\sof\sless\sthan\s100\sbytes.
-D 2015-06-27T15:51:06.913
+C Performance\simprovements\sin\smoveToChild()\sby\sshifting\ssome\swork\sover\nto\sgetAndInitPage().\s\sNet\simprovement\sis\sabout\s800K\scycles\sat\scost\sof\s30\sbytes.
+D 2015-06-27T19:45:03.070
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 285a0a234ed7610d431d91671c136098c2bd86a9
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -269,9 +269,9 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c be03b25d28cf714e81a825e60f7abcd8825e9b4e
+F src/btree.c b1ba9f65eba193ecae9519be29cce63bc1daef4c
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
-F src/btreeInt.h 426d1e0d1a15d06b3ad2304f4bedc5bb71e5b4a2
+F src/btreeInt.h 30f611b87ff873f47a28ce0bf66dd778c3274d9a
 F src/build.c b3f15255d5b16e42dafeaa638fd4f8a47c94ed70
 F src/callback.c 7b44ce59674338ad48b0e84e7b72f935ea4f68b0
 F src/complete.c a5cf5b4b56390cfb7b8636e8f7ddef90258dd575
@@ -1364,7 +1364,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 9383a688701ac2c366a308efc287c9c0f8977d4e
-R 16848ebaab74906a500d4e5002f1b1ec
+P 7f65b96b4017413bd19624570efe8fb2b0f7b991
+R 4df1944eb9c633cad9fdc689344e2d7e
 U drh
-Z a8b43d2118aa53b4955ba2ebec95dffb
+Z 093d236679649777c7df295c5a4c84ba

manifest.uuid

@@ -1 +1 @@
-7f65b96b4017413bd19624570efe8fb2b0f7b991
+1956a4ce8eca650d98a7f68fd2d82eb8a3d6069f

src/btree.c

@@ -1909,40 +1909,63 @@ u32 sqlite3BtreeLastPage(Btree *p){
 }
 
 /*
-** Get a page from the pager and initialize it.  This routine is just a
-** convenience wrapper around separate calls to btreeGetPage() and 
-** btreeInitPage().
+** Get a page from the pager and initialize it.
 **
-** If an error occurs, then the value *ppPage is set to is undefined. It
+** If pCur!=0 then the page acquired will be added to that cursor.
+** If the fetch fails, this routine must decrement pCur->iPage.
+**
+** The page is fetched as read-write unless pCur is not NULL and is
+** a read-only cursor.
+**
+** If an error occurs, then *ppPage is undefined. It
 ** may remain unchanged, or it may be set to an invalid value.
 */
 static int getAndInitPage(
   BtShared *pBt,                  /* The database file */
   Pgno pgno,                      /* Number of the page to get */
   MemPage **ppPage,               /* Write the page pointer here */
-  int bReadonly                   /* PAGER_GET_READONLY or 0 */
+  BtCursor *pCur,                 /* Cursor to receive the page, or NULL */
+  int bReadOnly                   /* True for a read-only page */
 ){
   int rc;
+  DbPage *pDbPage;
   assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( bReadonly==PAGER_GET_READONLY || bReadonly==0 );
+  assert( pCur==0 || ppPage==&pCur->apPage[pCur->iPage] );
+  assert( pCur==0 || bReadOnly==pCur->curPagerFlags );
 
   if( pgno>btreePagecount(pBt) ){
     rc = SQLITE_CORRUPT_BKPT;
-  }else{
-    DbPage *pDbPage;
-    rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadonly);
-    if( rc ) return rc;
-    *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
-    if( (*ppPage)->isInit==0 ){
-      rc = btreeInitPage(*ppPage);
-      if( rc!=SQLITE_OK ){
-        releasePage(*ppPage);
-      }
+    goto getAndInitPage_error;
+  }
+  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
+  if( rc ){
+    goto getAndInitPage_error;
+  }
+  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
+  if( (*ppPage)->isInit==0 ){
+    rc = btreeInitPage(*ppPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(*ppPage);
+      goto getAndInitPage_error;
     }
   }
 
+  /* If obtaining a page for a cursor, we must verify that the page is
+  ** compatible with the cursor */
+  if( pCur && pCur->iPage>0
+   && ((*ppPage)->nCell<1 || (*ppPage)->intKey!=pCur->apPage[0]->intKey)
+  ){
+    rc = SQLITE_CORRUPT_BKPT;
+    releasePage(*ppPage);
+    goto getAndInitPage_error;
+  }
+
   testcase( pgno==0 );
   assert( pgno!=0 || rc==SQLITE_CORRUPT );
+  return SQLITE_OK;
+
+getAndInitPage_error:
+  if( pCur ) pCur->iPage--;
   return rc;
 }
 
@@ -4028,6 +4051,7 @@ static int btreeCursor(
   pCur->pBt = pBt;
   assert( wrFlag==0 || wrFlag==BTCF_WriteFlag );
   pCur->curFlags = wrFlag;
+  pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY;
   pCur->pNext = pBt->pCursor;
   if( pCur->pNext ){
     pCur->pNext->pPrev = pCur;
@@ -4641,9 +4665,6 @@ const void *sqlite3BtreeDataFetch(BtCursor *pCur, u32 *pAmt){
 ** vice-versa).
 */
 static int moveToChild(BtCursor *pCur, u32 newPgno){
-  int rc;
-  int i = pCur->iPage;
-  MemPage *pNewPage;
   BtShared *pBt = pCur->pBt;
 
   assert( cursorHoldsMutex(pCur) );
@@ -4653,19 +4674,12 @@ static int moveToChild(BtCursor *pCur, u32 newPgno){
   if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
     return SQLITE_CORRUPT_BKPT;
   }
-  rc = getAndInitPage(pBt, newPgno, &pNewPage,
-               (pCur->curFlags & BTCF_WriteFlag)==0 ? PAGER_GET_READONLY : 0);
-  if( rc ) return rc;
-  pCur->apPage[i+1] = pNewPage;
-  pCur->aiIdx[i+1] = 0;
-  pCur->iPage++;
-
   pCur->info.nSize = 0;
   pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  if( pNewPage->nCell<1 || pNewPage->intKey!=pCur->apPage[i]->intKey ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  return SQLITE_OK;
+  pCur->iPage++;
+  pCur->aiIdx[pCur->iPage] = 0;
+  return getAndInitPage(pBt, newPgno, &pCur->apPage[pCur->iPage],
+                        pCur, pCur->curPagerFlags);
 }
 
 #if SQLITE_DEBUG
@@ -4760,8 +4774,10 @@ static int moveToRoot(BtCursor *pCur){
     pCur->eState = CURSOR_INVALID;
     return SQLITE_OK;
   }else{
+    assert( pCur->iPage==(-1) );
+    pCur->iPage = 0;
     rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
-                 (pCur->curFlags & BTCF_WriteFlag)==0 ? PAGER_GET_READONLY : 0);
+                        pCur, pCur->curPagerFlags);
     if( rc!=SQLITE_OK ){
       pCur->eState = CURSOR_INVALID;
       return rc;
@@ -6963,7 +6979,7 @@ static int balance_nonroot(
   }
   pgno = get4byte(pRight);
   while( 1 ){
-    rc = getAndInitPage(pBt, pgno, &apOld[i], 0);
+    rc = getAndInitPage(pBt, pgno, &apOld[i], 0, 0);
     if( rc ){
       memset(apOld, 0, (i+1)*sizeof(MemPage*));
       goto balance_cleanup;
@@ -8280,7 +8296,7 @@ static int clearDatabasePage(
   if( pgno>btreePagecount(pBt) ){
     return SQLITE_CORRUPT_BKPT;
   }
-  rc = getAndInitPage(pBt, pgno, &pPage, 0);
+  rc = getAndInitPage(pBt, pgno, &pPage, 0, 0);
   if( rc ) return rc;
   if( pPage->bBusy ){
     rc = SQLITE_CORRUPT_BKPT;

src/btreeInt.h

@@ -518,6 +518,7 @@ struct BtCursor {
   int skipNext;    /* Prev() is noop if negative. Next() is noop if positive.
                    ** Error code if eState==CURSOR_FAULT */
   u8 curFlags;              /* zero or more BTCF_* flags defined below */
+  u8 curPagerFlags;         /* Flags to send to sqlite3PagerAcquire() */
   u8 eState;                /* One of the CURSOR_XXX constants (see below) */
   u8 hints;                             /* As configured by CursorSetHints() */
   i16 iPage;                            /* Index of current page in apPage */