From: drh <>
Date: Thu, 7 Jul 2022 21:04:03 +0000 (+0000)
Subject: Size reduction and performance increase in defragementPage() of btree.c.
X-Git-Tag: version-3.40.0~330
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f15b77b7cfdad810bdac026d13ff6aef31022f21;p=thirdparty%2Fsqlite.git

Size reduction and performance increase in defragementPage() of btree.c.

FossilOrigin-Name: 1b03f197b5572084177012a58990f8dba7ff10382ff5657fda62867a4d0b1af9
---

diff --git a/manifest b/manifest
index 06040bca47..833eb98008 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Size\sreduction\sand\sperformance\sincrease\sin\sthe\spageFindSlot()\sroutine\sof\nbtree.c.
-D 2022-07-07T20:29:49.982
+C Size\sreduction\sand\sperformance\sincrease\sin\sdefragementPage()\sof\sbtree.c.
+D 2022-07-07T21:04:03.223
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -510,7 +510,7 @@ F src/auth.c f4fa91b6a90bbc8e0d0f738aa284551739c9543a367071f55574681e0f24f8cf
 F src/backup.c a2891172438e385fdbe97c11c9745676bec54f518d4447090af97189fd8e52d7
 F src/bitvec.c 7c849aac407230278445cb069bebc5f89bf2ddd87c5ed9459b070a9175707b3d
 F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
-F src/btree.c 6599d972b674cbbcb76e9a9db0e206d3bf9b60186464c08ef82ab6fda0622d44
+F src/btree.c 85e73fcdad6ca71caf083427d7a84ee31bce23a844f0ca3dd41f176f905090c9
 F src/btree.h 74d64b8f28cfa4a894d14d4ed64fa432cd697b98b61708d4351482ae15913e22
 F src/btreeInt.h 8ce1332edd89dfd2461d561ac10a0ab5601c8e06200cb5230596c3caaf54482e
 F src/build.c 23f874642825d7eaaeeb7a3281b2b1a75e1d4c4dd9ae4dceddcd908266634214
@@ -1979,8 +1979,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 7d7aed053f600659c63d8bac6d5da77879936c3fc57bfd058a4943b3bc530575
-R 573750a14fc9838f7267df2add226c79
+P 5d247e38560b97975568e8a48324acaca1002ec2ef7fa3efc9c8aa7d83412aad
+R a83c6075a9fd94646d9131a381899d86
 U drh
-Z 6e9989a326ed7411def6db942d22ad53
+Z fd00ac09a5e7246ba9e920ca18028a40
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 5f4865c9bd..a69143fe3c 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-5d247e38560b97975568e8a48324acaca1002ec2ef7fa3efc9c8aa7d83412aad
\ No newline at end of file
+1b03f197b5572084177012a58990f8dba7ff10382ff5657fda62867a4d0b1af9
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 2d2a20cd52..bdcf5b1478 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -1513,7 +1513,6 @@ static int defragmentPage(MemPage *pPage, int nMaxFrag){
   assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
   assert( pPage->nOverflow==0 );
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  temp = 0;
   src = data = pPage->aData;
   hdr = pPage->hdrOffset;
   cellOffset = pPage->cellOffset;
@@ -1568,39 +1567,38 @@ static int defragmentPage(MemPage *pPage, int nMaxFrag){
   cbrk = usableSize;
   iCellLast = usableSize - 4;
   iCellStart = get2byte(&data[hdr+5]);
-  for(i=0; i<nCell; i++){
-    u8 *pAddr;     /* The i-th cell pointer */
-    pAddr = &data[cellOffset + i*2];
-    pc = get2byte(pAddr);
-    testcase( pc==iCellFirst );
-    testcase( pc==iCellLast );
-    /* These conditions have already been verified in btreeInitPage()
-    ** if PRAGMA cell_size_check=ON.
-    */
-    if( pc<iCellStart || pc>iCellLast ){
-      return SQLITE_CORRUPT_PAGE(pPage);
-    }
-    assert( pc>=iCellStart && pc<=iCellLast );
-    size = pPage->xCellSize(pPage, &src[pc]);
-    cbrk -= size;
-    if( cbrk<iCellStart || pc+size>usableSize ){
-      return SQLITE_CORRUPT_PAGE(pPage);
-    }
-    assert( cbrk+size<=usableSize && cbrk>=iCellStart );
-    testcase( cbrk+size==usableSize );
-    testcase( pc+size==usableSize );
-    put2byte(pAddr, cbrk);
-    if( temp==0 ){
-      if( cbrk==pc ) continue;
-      temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
-      memcpy(&temp[iCellStart], &data[iCellStart], usableSize - iCellStart);
-      src = temp;
+  if( nCell>0 ){
+    temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
+    memcpy(&temp[iCellStart], &data[iCellStart], usableSize - iCellStart);
+    src = temp;
+    for(i=0; i<nCell; i++){
+      u8 *pAddr;     /* The i-th cell pointer */
+      pAddr = &data[cellOffset + i*2];
+      pc = get2byte(pAddr);
+      testcase( pc==iCellFirst );
+      testcase( pc==iCellLast );
+      /* These conditions have already been verified in btreeInitPage()
+      ** if PRAGMA cell_size_check=ON.
+      */
+      if( pc<iCellStart || pc>iCellLast ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      assert( pc>=iCellStart && pc<=iCellLast );
+      size = pPage->xCellSize(pPage, &src[pc]);
+      cbrk -= size;
+      if( cbrk<iCellStart || pc+size>usableSize ){
+        return SQLITE_CORRUPT_PAGE(pPage);
+      }
+      assert( cbrk+size<=usableSize && cbrk>=iCellStart );
+      testcase( cbrk+size==usableSize );
+      testcase( pc+size==usableSize );
+      put2byte(pAddr, cbrk);
+      memcpy(&data[cbrk], &src[pc], size);
     }
-    memcpy(&data[cbrk], &src[pc], size);
   }
   data[hdr+7] = 0;
 
- defragment_out:
+defragment_out:
   assert( pPage->nFree>=0 );
   if( data[hdr+7]+cbrk-iCellFirst!=pPage->nFree ){
     return SQLITE_CORRUPT_PAGE(pPage);