Optimization: Try to avoid unnecessary btree searching when repositioning

a cursor to the next row.

FossilOrigin-Name: ee793d30c1dc1f78f49e6230d17750eceedbd8ed

1 files changed, 20 insertions, 3 deletions

diff --git a/src/btree.c b/src/btree.c
index fb0565591..b6bc66ea8 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -5091,9 +5091,26 @@ int sqlite3BtreeMovetoUnpacked(
       *pRes = 0;
       return SQLITE_OK;
     }
-    if( (pCur->curFlags & BTCF_AtLast)!=0 && pCur->info.nKey<intKey ){
-      *pRes = -1;
-      return SQLITE_OK;
+    if( pCur->info.nKey<intKey ){
+      if( (pCur->curFlags & BTCF_AtLast)!=0 ){
+        *pRes = -1;
+        return SQLITE_OK;
+      }
+      /* If the requested key is one more than the previous key, then
+      ** try to get there using sqlite3BtreeNext() rather than a full
+      ** binary search.  This is an optimization only.  The correct answer
+      ** is still obtained without this ase, only a little more slowely */
+      if( pCur->info.nKey+1==intKey && !pCur->skipNext ){
+        *pRes = 0;
+        rc = sqlite3BtreeNext(pCur, pRes);
+        if( rc ) return rc;
+        if( *pRes==0 ){
+          getCellInfo(pCur);
+          if( pCur->info.nKey==intKey ){
+            return SQLITE_OK;
+          }
+        }
+      }
     }
   }