From: drh <drh@noemail.net>
Date: Tue, 23 Jun 2015 14:49:42 +0000 (+0000)
Subject: Improvements to the way balance_nonroot() constructs the b.apCell array of
X-Git-Tag: version-3.8.11~142^2~5
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4edfdd38fb16c75d03403e3da2ae1860bb44e0bc;p=thirdparty%2Fsqlite.git

Improvements to the way balance_nonroot() constructs the b.apCell array of
pointers to cells.

FossilOrigin-Name: ee44bb25b2a88e25ba2afe37cf03ba199692a3a0
---

diff --git a/manifest b/manifest
index ea07d936b3..44f122c617 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Merge\sthe\scompound\sSELECT\soperator\sfix\sfrom\strunk.
-D 2015-06-23T13:02:10.077
+C Improvements\sto\sthe\sway\sbalance_nonroot()\sconstructs\sthe\sb.apCell\sarray\sof\npointers\sto\scells.
+D 2015-06-23T14:49:42.852
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 1063c58075b7400d93326b0eb332b48a54f53025
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -192,7 +192,7 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c e6ac65de1742116fb5abbb106a26eb5bf48cd79e
+F src/btree.c 8d772673dc249aee6b6e65e4285291f7f2565ffd
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
 F src/btreeInt.h 6ece2dd9c8e2eac05f0a8ded8772a44e96486c65
 F src/build.c b3f15255d5b16e42dafeaa638fd4f8a47c94ed70
@@ -1286,7 +1286,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 43844537e8a372953386663f8177202901ba7566 4df852ce26c95d5d23c83dbe9c59d2c3435acddf
-R 5a31f6e2047c6b2a76413665b07fcf29
+P a7be554f4b8534fc237fa4c6defc38fcd4049707
+R 4ad5f5185dfc9700d38a61349b40bf79
 U drh
-Z ef941435462213fb596e80b11c30b19f
+Z 77f5541f0ad6043b85ab2e262249ce69
diff --git a/manifest.uuid b/manifest.uuid
index c792bcaca0..c1bc1337b1 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-a7be554f4b8534fc237fa4c6defc38fcd4049707
\ No newline at end of file
+ee44bb25b2a88e25ba2afe37cf03ba199692a3a0
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 9693b0d393..adba9ec45e 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -958,27 +958,25 @@ static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
   ((P)->aData + ((P)->maskPage & get2byte(&(P)->aCellIdx[2*(I)])))
 #define findCellv2(D,M,O,I) (D+(M&get2byte(D+(O+2*(I)))))
 
-
 /*
-** This a more complex version of findCell() that works for
-** pages that do contain overflow cells.
+** Sort the overflow cells of a page into index order.
+**
+** An O(N*N) algorithm is used.  But that should not be a problem
+** since N is only very rarely more than 1.
 */
-static u8 *findOverflowCell(MemPage *pPage, int iCell){
-  int i;
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  for(i=pPage->nOverflow-1; i>=0; i--){
-    int k;
-    k = pPage->aiOvfl[i];
-    if( k<=iCell ){
-      if( k==iCell ){
-        return pPage->apOvfl[i];
+static void btreeSortOverflow(MemPage *p){
+  int j, k;
+  for(j=0; j<p->nOverflow-1; j++){
+    for(k=j+1; k<p->nOverflow; k++){
+      if( p->aiOvfl[j]>p->aiOvfl[k] ){
+        SWAP(u16, p->aiOvfl[j], p->aiOvfl[k]);
+        SWAP(u8*, p->apOvfl[j], p->apOvfl[k]);
       }
-      iCell--;
     }
   }
-  return findCell(pPage, iCell);
 }
 
+
 /*
 ** This is common tail processing for btreeParseCellPtr() and
 ** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
@@ -7057,8 +7055,11 @@ static int balance_nonroot(
   leafCorrection = b.pRef->leaf*4;
   leafData = b.pRef->intKeyLeaf;
   for(i=0; i<nOld; i++){
-    int limit;
     MemPage *pOld = apOld[i];
+    int limit = pOld->nCell;
+    u8 *aData = pOld->aData;
+    u16 maskPage = pOld->maskPage;
+    u16 cellOffset = pOld->cellOffset;
 
     /* Verify that all sibling pages are of the same "type" (table-leaf,
     ** table-interior, index-leaf, or index-interior).
@@ -7068,24 +7069,38 @@ static int balance_nonroot(
       goto balance_cleanup;
     }
 
-    limit = pOld->nCell+pOld->nOverflow;
+    /* Load b.apCell[] with pointers to all cells in pOld.  Intersperse
+    ** overflow cells in the correct sequence.  
+    **
+    ** This must be done in advance.  Once the balance starts, the cell
+    ** offset section of the btree page will be overwritten and we will no
+    ** long be able to find the cells if a pointer to each cell is not saved
+    ** first.
+    */
     memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*limit);
+    j = 0;
     if( pOld->nOverflow>0 ){
-      for(j=0; j<limit; j++){
-        assert( b.nCell<nMaxCells );
-        b.apCell[b.nCell] = findOverflowCell(pOld, j);
-        b.nCell++;
-      }
-    }else{
-      u8 *aData = pOld->aData;
-      u16 maskPage = pOld->maskPage;
-      u16 cellOffset = pOld->cellOffset;
-      for(j=0; j<limit; j++){
-        assert( b.nCell<nMaxCells );
-        b.apCell[b.nCell] = findCellv2(aData, maskPage, cellOffset, j);
+      memset(&b.szCell[b.nCell+limit], 0, sizeof(b.szCell[0])*pOld->nOverflow);
+      btreeSortOverflow(pOld);
+      for(k=0; k<pOld->nOverflow; k++){
+        limit = pOld->aiOvfl[k] - k;
+        while( j<limit ){
+          b.apCell[b.nCell] = findCellv2(aData, maskPage, cellOffset, j);
+          b.nCell++;
+          j++;
+        }
+        b.apCell[b.nCell] = pOld->apOvfl[k];
         b.nCell++;
       }
+      limit = pOld->nCell;
     }
+    while( j<limit ){
+      assert( b.nCell<nMaxCells );
+      b.apCell[b.nCell] = findCellv2(aData, maskPage, cellOffset, j);
+      b.nCell++;
+      j++;
+    }
+
     cntOld[i] = b.nCell;
     if( i<nOld-1 && !leafData){
       u16 sz = (u16)szNew[i];