From: drh <>
Date: Sun, 2 Jan 2022 14:55:43 +0000 (+0000)
Subject: Small performance optimization and size reduction in sqlite3BtreeDelete().
X-Git-Tag: version-3.38.0~133
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7e17a3abbe7f1b644661c7e5ededd4679dd1b409;p=thirdparty%2Fsqlite.git

Small performance optimization and size reduction in sqlite3BtreeDelete().

FossilOrigin-Name: da0af4dd9ba4180a16543fac1549fd4ccecdc66dcf6d275f77de21fd80708882
---

diff --git a/manifest b/manifest
index 28d5395d04..fee691766c 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Clear\sthe\scache\sof\striggers\sused\sto\simplement\sCASCADE\sforeign\skey\sconstraints\nwhenever\sthe\sschema\schanges.\s\sFix\sfor\sthe\sproblem\sidentified\sby\n[forum:/forumpost/2831335356|forum\spost\s2831335356].
-D 2022-01-02T12:01:03.636
+C Small\sperformance\soptimization\sand\ssize\sreduction\sin\ssqlite3BtreeDelete().
+D 2022-01-02T14:55:43.095
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -491,7 +491,7 @@ F src/auth.c f4fa91b6a90bbc8e0d0f738aa284551739c9543a367071f55574681e0f24f8cf
 F src/backup.c 3014889fa06e20e6adfa0d07b60097eec1f6e5b06671625f476a714d2356513d
 F src/bitvec.c 7c849aac407230278445cb069bebc5f89bf2ddd87c5ed9459b070a9175707b3d
 F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
-F src/btree.c fab3d2a9e2a187373c393b9f35e68e996010a1aae1354763f7c5846915a99b83
+F src/btree.c d4b6e026d85b47018dd4c31b42dd490ed22d4320917e705d6502e589d1a8227d
 F src/btree.h 74d64b8f28cfa4a894d14d4ed64fa432cd697b98b61708d4351482ae15913e22
 F src/btreeInt.h ee9348c4cb9077243b049edc93a82c1f32ca48baeabf2140d41362b9f9139ff7
 F src/build.c 6e16f7b539bfc55149a039bf0cda26b089640339df6147070b072df2d1c4f771
@@ -1936,8 +1936,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 13e9ff9e84a114374b49986484dbee05953a496f3017dd5089fba6f495a17c40
-R 55a4ceae34dc12d0aa858af0c296a260
+P 5232c9777fe4fb13e1ecfe5b5d644e2c45d0514f95884dbed49a03fb9b67304c
+R aa110e7b5297811807e4f693fefdef54
 U drh
-Z 356b59ab85226987dbc745e5cdcb40e4
+Z a31d2467491c7884583c9d9e2a7c5425
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 4b00d43ad0..71edf50ae9 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-5232c9777fe4fb13e1ecfe5b5d644e2c45d0514f95884dbed49a03fb9b67304c
\ No newline at end of file
+da0af4dd9ba4180a16543fac1549fd4ccecdc66dcf6d275f77de21fd80708882
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index cfaffb7d7e..4f777f0f75 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9229,14 +9229,13 @@ int sqlite3BtreeTransferRow(BtCursor *pDest, BtCursor *pSrc, i64 iKey){
 int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
   Btree *p = pCur->pBtree;
   BtShared *pBt = p->pBt;              
-  int rc;                              /* Return code */
-  MemPage *pPage;                      /* Page to delete cell from */
-  unsigned char *pCell;                /* Pointer to cell to delete */
-  int iCellIdx;                        /* Index of cell to delete */
-  int iCellDepth;                      /* Depth of node containing pCell */ 
-  CellInfo info;                       /* Size of the cell being deleted */
-  int bSkipnext = 0;                   /* Leaf cursor in SKIPNEXT state */
-  u8 bPreserve = flags & BTREE_SAVEPOSITION;  /* Keep cursor valid */
+  int rc;                    /* Return code */
+  MemPage *pPage;            /* Page to delete cell from */
+  unsigned char *pCell;      /* Pointer to cell to delete */
+  int iCellIdx;              /* Index of cell to delete */
+  int iCellDepth;            /* Depth of node containing pCell */ 
+  CellInfo info;             /* Size of the cell being deleted */
+  u8 bPreserve;              /* Keep cursor valid.  2 for CURSOR_SKIPNEXT */
 
   assert( cursorOwnsBtShared(pCur) );
   assert( pBt->inTransaction==TRANS_WRITE );
@@ -9255,23 +9254,31 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
   iCellDepth = pCur->iPage;
   iCellIdx = pCur->ix;
   pPage = pCur->pPage;
-  pCell = findCell(pPage, iCellIdx);
-  if( pPage->nFree<0 && btreeComputeFreeSpace(pPage) ){
+  if( pPage->nCell<=iCellIdx ){
     return SQLITE_CORRUPT_BKPT;
   }
-  if( pPage->nCell<=iCellIdx ){
+  pCell = findCell(pPage, iCellIdx);
+  if( pPage->nFree<0 && btreeComputeFreeSpace(pPage) ){
     return SQLITE_CORRUPT_BKPT;
   }
 
-  /* If the bPreserve flag is set to true, then the cursor position must
+  /* If the BTREE_SAVEPOSITION bit is on, then the cursor position must
   ** be preserved following this delete operation. If the current delete
   ** will cause a b-tree rebalance, then this is done by saving the cursor
   ** key and leaving the cursor in CURSOR_REQUIRESEEK state before 
   ** returning. 
   **
-  ** Or, if the current delete will not cause a rebalance, then the cursor
+  ** If the current delete will not cause a rebalance, then the cursor
   ** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
-  ** before or after the deleted entry. In this case set bSkipnext to true.  */
+  ** before or after the deleted entry.
+  **
+  ** The bPreserve value records which path is required:
+  **
+  **    bPreserve==0         Not necessary to save the cursor position
+  **    bPreserve==1         Use CURSOR_REQUIRESEEK to save the cursor position
+  **    bPreserve==2         Cursor won't move.  Set CURSOR_SKIPNEXT.
+  */
+  bPreserve = (flags & BTREE_SAVEPOSITION)!=0;
   if( bPreserve ){
     if( !pPage->leaf 
      || (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
@@ -9282,7 +9289,7 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
       rc = saveCursorKey(pCur);
       if( rc ) return rc;
     }else{
-      bSkipnext = 1;
+      bPreserve = 2;
     }
   }
 
@@ -9382,8 +9389,8 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
   }
 
   if( rc==SQLITE_OK ){
-    if( bSkipnext ){
-      assert( bPreserve && (pCur->iPage==iCellDepth || CORRUPT_DB) );
+    if( bPreserve>1 ){
+      assert( (pCur->iPage==iCellDepth || CORRUPT_DB) );
       assert( pPage==pCur->pPage || CORRUPT_DB );
       assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
       pCur->eState = CURSOR_SKIPNEXT;