In function moveToRoot(), use the MemPage.pParent pointers to find the root page if they are valid. This is slightly faster than requesting a new reference to the root page from the pager layer. (CVS 5725)

FossilOrigin-Name: 0c8b74e668b7462c5439c04993d1d7cd74210075

manifest

@@ -1,5 +1,5 @@
-C In\ssqlite3BtreeGetMeta(),\sif\sBtShared.pPage1\sis\savailable\suse\sit\sinstead\sof\srequesting\sa\snew\sreference\sfrom\sthe\spager\slayer.\s(CVS\s5724)
-D 2008-09-19T15:10:58
+C In\sfunction\smoveToRoot(),\suse\sthe\sMemPage.pParent\spointers\sto\sfind\sthe\sroot\spage\sif\sthey\sare\svalid.\sThis\sis\sslightly\sfaster\sthan\srequesting\sa\snew\sreference\sto\sthe\sroot\spage\sfrom\sthe\spager\slayer.\s(CVS\s5725)
+D 2008-09-19T16:39:38
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in d15a7ebfe5e057a72a49805ffb302dbb601c8329
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -99,7 +99,7 @@ F src/attach.c db3f4a60538733c1e4dcb9d0217a6e0d6ccd615b
 F src/auth.c c8b2ab5c8bad4bd90ed7c294694f48269162c627
 F src/bitvec.c 95c86bd18d8fedf0533f5af196192546e10a7e7d
 F src/btmutex.c 709cad2cdca0afd013f0f612363810e53f59ec53
-F src/btree.c cfe8dbbaa75f587653f33121c3e82999c65069ae
+F src/btree.c 4d642d23fc4507089f702eb24b506be2ce7e0efd
 F src/btree.h 6371c5e599fab391a150c96afbc10062b276d107
 F src/btreeInt.h e36f77e6621d671beb19ae581af1eba116cdfdc4
 F src/build.c 160c71acca8f643f436ed6c1ee2f684c88df4dfe
@@ -637,7 +637,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 1dbced29de5f59ba2ebf877edcadf171540374d1
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 75deaa442f3a363c4ea5b6f0e510306feeaa8915
-R 62a9176bcf4a5c57a6633d26293ede50
+P 59be34cfa4fe74f7e5b547c55d273ecba9d7796c
+R f3d27e1b16af35370468dd13d616f41c
 U danielk1977
-Z 89134c443f08e4715d35e3ebe96ef424
+Z c019239d82228e28c9df258ace82b690

manifest.uuid

@@ -1 +1 @@
-59be34cfa4fe74f7e5b547c55d273ecba9d7796c
+0c8b74e668b7462c5439c04993d1d7cd74210075

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.515 2008/09/19 15:10:58 danielk1977 Exp $
+** $Id: btree.c,v 1.516 2008/09/19 16:39:38 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -3564,8 +3564,22 @@ static int moveToRoot(BtCursor *pCur){
     clearCursorPosition(pCur);
   }
   pRoot = pCur->pPage;
-  if( pRoot && pRoot->pgno==pCur->pgnoRoot ){
+  if( pRoot && pRoot->isInit ){
+    /* If the page the cursor is currently pointing to is fully initialized,
+    ** then the root page can be found by following the MemPage.pParent
+    ** pointers. This is faster than requesting a reference to the root
+    ** page from the pager layer.
+    */
+    while( pRoot->pParent ){
+      assert( pRoot->isInit==PAGE_ISINIT_FULL );
+      pRoot = pRoot->pParent;
+    }
     assert( pRoot->isInit==PAGE_ISINIT_FULL );
+    if( pRoot!=pCur->pPage ){
+      sqlite3PagerRef(pRoot->pDbPage);
+      releasePage(pCur->pPage);
+      pCur->pPage = pRoot;
+    }
   }else{
     if( 
       SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0))
@@ -3576,6 +3590,7 @@ static int moveToRoot(BtCursor *pCur){
     releasePage(pCur->pPage);
     pCur->pPage = pRoot;
   }
+  assert( pCur->pPage->pgno==pCur->pgnoRoot );
   pCur->idx = 0;
   pCur->info.nSize = 0;
   pCur->atLast = 0;
@@ -3745,7 +3760,6 @@ int sqlite3BtreeMovetoUnpacked(
     }
   }
 
-
   rc = moveToRoot(pCur);
   if( rc ){
     return rc;
@@ -6472,18 +6486,29 @@ int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
   }
 
   assert( idx>=0 && idx<=15 );
-  if( !pBt->pPage1 ){
+  if( pBt->pPage1 ){
+    /* The b-tree is already holding a reference to page 1 of the database
+    ** file. In this case the required meta-data value can be read directly
+    ** from the page data of this reference. This is slightly faster than
+    ** requesting a new reference from the pager layer.
+    */
+    pP1 = (unsigned char *)pBt->pPage1->aData;
+  }else{
+    /* The b-tree does not have a reference to page 1 of the database file.
+    ** Obtain one from the pager layer.
+    */
     rc = sqlite3PagerGet(pBt->pPager, 1, &pDbPage);
     if( rc ){
       sqlite3BtreeLeave(p);
       return rc;
     }
     pP1 = (unsigned char *)sqlite3PagerGetData(pDbPage);
-  }else{
-    pP1 = (unsigned char *)pBt->pPage1->aData;
   }
   *pMeta = get4byte(&pP1[36 + idx*4]);
 
+  /* If the b-tree is not holding a reference to page 1, then one was 
+  ** requested from the pager layer in the above block. Release it now.
+  */
   if( !pBt->pPage1 ){
     sqlite3PagerUnref(pDbPage);
   }