More simplifications and performance improvements to cell allocation

logic associated with allocateSpace().

FossilOrigin-Name: 78da0f69cb3289e332018864004f319f2764a5c8

diff --git a/manifest b/manifest
index fbf418370ded35744238140ced63b285862d03dd..848f3d66c676735954daa15d0438a28df5958418 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Reorder\sthe\sterms\sof\sa\sconditional\sfor\sa\ssmall\sperformance\sgain.
-D 2015-06-25T16:01:44.112
+C More\ssimplifications\sand\sperformance\simprovements\sto\scell\sallocation\nlogic\sassociated\swith\sallocateSpace().
+D 2015-06-25T18:36:13.826
 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 85679f63ebc2c67593479cf22f88539f71f2af70
+F src/btree.c 960a641306010ed25690af8e05d599fe4b9a005d
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
 F src/btreeInt.h fdd1aff02fb2a63812bd95716e7f579fc3759107
 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 f824e66b0dc120bed227c7446e2663fcad7cc4f6
-R 8aa067d659e72dd17b19d63682b0eebd
+P d67b0ed1054cbb7ea2cdd74720d4d6e0227cec14
+R 4a51cc2794802bb6f018a7f1798d3a79
 U drh
-Z c674ba4fda0e43aa32d59f882342a9d7
+Z 2ec930a14eaee4b6a3bd2ab311de6bca

diff --git a/manifest.uuid b/manifest.uuid
index 67e0ce0f605e62229ba65b8e265067aa09d10b5a..6e77614794bfababa7415039ed499a11d1aa1bb6 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-d67b0ed1054cbb7ea2cdd74720d4d6e0227cec14
\ No newline at end of file
+78da0f69cb3289e332018864004f319f2764a5c8
\ No newline at end of file

diff --git a/src/btree.c b/src/btree.c
index 646367c2e0af32ba8d609daa804304a981b80961..9dbdab9b74c07fd8e6fcf5cdf73b05f71e7e1fec 100644 (file)
--- a/src/btree.c
+++ b/src/btree.c
@@ -1351,18 +1351,20 @@ static int defragmentPage(MemPage *pPage){
 ** This function may detect corruption within pPg.  If corruption is
 ** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
 **
-** If a slot of at least nByte bytes is found but cannot be used because 
-** there are already at least 60 fragmented bytes on the page, return NULL.
-** In this case, if pbDefrag parameter is not NULL, set *pbDefrag to true.
+** Slots on the free list that are between 1 and 3 bytes larger than nByte
+** will be ignored if adding the extra space to the fragmentation count
+** causes the fragmentation count to exceed 60.
 */
-static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
+static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
   const int hdr = pPg->hdrOffset;
   u8 * const aData = pPg->aData;
-  int iAddr;
-  int pc;
+  int iAddr = hdr + 1;
+  int pc = get2byte(&aData[iAddr]);
+  int x;
   int usableSize = pPg->pBt->usableSize;
 
-  for(iAddr=hdr+1; (pc = get2byte(&aData[iAddr]))>0; iAddr=pc){
+  assert( pc>0 );
+  do{
     int size;            /* Size of the free slot */
     /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
     ** increasing offset. */
@@ -1374,8 +1376,7 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
     ** freeblock form a big-endian integer which is the size of the freeblock
     ** in bytes, including the 4-byte header. */
     size = get2byte(&aData[pc+2]);
-    if( size>=nByte ){
-      int x = size - nByte;
+    if( (x = size - nByte)>=0 ){
       testcase( x==4 );
       testcase( x==3 );
       if( pc < pPg->cellOffset+2*pPg->nCell || size+pc > usableSize ){
@@ -1384,10 +1385,8 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
       }else if( x<4 ){
         /* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
         ** number of bytes in fragments may not exceed 60. */
-        if( aData[hdr+7]>=60 ){
-          if( pbDefrag ) *pbDefrag = 1;
-          return 0;
-        }
+        if( aData[hdr+7]>57 ) return 0;
+
         /* Remove the slot from the free-list. Update the number of
         ** fragmented bytes within the page. */
         memcpy(&aData[iAddr], &aData[pc], 2);
@@ -1399,7 +1398,9 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
       }
       return &aData[pc + x];
     }
-  }
+    iAddr = pc;
+    pc = get2byte(&aData[pc]);
+  }while( pc );
 
   return 0;
 }
@@ -1458,14 +1459,13 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   testcase( gap+1==top );
   testcase( gap==top );
   if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
-    int bDefrag = 0;
-    u8 *pSpace = pageFindSlot(pPage, nByte, &rc, &bDefrag);
-    if( rc ) return rc;
-    if( bDefrag ) goto defragment_page;
+    u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
     if( pSpace ){
       assert( pSpace>=data && (pSpace - data)<65536 );
       *pIdx = (int)(pSpace - data);
       return SQLITE_OK;
+    }else if( rc ){
+      return rc;
     }
   }
 
@@ -1474,7 +1474,6 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   */
   testcase( gap+2+nByte==top );
   if( gap+2+nByte>top ){
- defragment_page:
     assert( pPage->nCell>0 || CORRUPT_DB );
     rc = defragmentPage(pPage);
     if( rc ) return rc;
@@ -6414,14 +6413,13 @@ static int pageInsertArray(
   int i;
   u8 *aData = pPg->aData;
   u8 *pData = *ppData;
-  const int bFreelist = aData[1] || aData[2];
   int iEnd = iFirst + nCell;
   assert( CORRUPT_DB || pPg->hdrOffset==0 );    /* Never called on page 1 */
   for(i=iFirst; i<iEnd; i++){
     int sz, rc;
     u8 *pSlot;
     sz = cachedCellSize(pCArray, i);
-    if( bFreelist==0 || (pSlot = pageFindSlot(pPg, sz, &rc, 0))==0 ){
+    if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
       pData -= sz;
       if( pData<pBegin ) return 1;
       pSlot = pData;