B-tree optimization: When seeking on a rowid table that has already been

positioned, check to see if the new row happens to be the next row on the
same leaf page.  That is a reasonably common case, and if it is true it
avoids a full binary search.

FossilOrigin-Name: 8e5cfb2039126da7689c4b1c88760f10e1234eaf

manifest

@@ -1,5 +1,5 @@
-C Change\ssqlite3_blob_reopen()\sto\scall\ssqlite3VdbeExec()\sdirectly\srather\sthan\ngoing\sthrough\ssqlite3_step().\s\sPerformance\senhancement.
-D 2017-01-21T16:27:56.517
+C B-tree\soptimization:\s\sWhen\sseeking\son\sa\srowid\stable\sthat\shas\salready\sbeen\npositioned,\scheck\sto\ssee\sif\sthe\snew\srow\shappens\sto\sbe\sthe\snext\srow\son\sthe\nsame\sleaf\spage.\s\sThat\sis\sa\sreasonably\scommon\scase,\sand\sif\sit\sis\strue\sit\navoids\sa\sfull\sbinary\ssearch.
+D 2017-01-21T16:54:19.338
 F Makefile.in 41bd4cad981487345c4a84081074bcdb876e4b2e
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc b8ca53350ae545e3562403d5da2a69cec79308da
@@ -333,7 +333,7 @@ F src/auth.c 930b376a9c56998557367e6f7f8aaeac82a2a792
 F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
-F src/btree.c e6b8f39d7dd1ad65f1747956de36f2595172a23d
+F src/btree.c 972b7e1346eb2f4369cf8cc43117c728e2bd9cd4
 F src/btree.h e6d352808956ec163a17f832193a3e198b3fb0ac
 F src/btreeInt.h 10c4b77c2fb399580babbcc7cf652ac10dba796e
 F src/build.c 9e799f1edd910dfa8a0bc29bd390d35d310596af
@@ -1547,7 +1547,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0d1ad13a296b22d6fe36879b56f99bd6af1acd3a
-R 6bebf342d641742884692400aca75850
+P 347df3c1fd7322e7aacaf1e9f8be81830947c482
+R 3888200d85fb0a6e771ec0a3c9f2e5a8
 U drh
-Z fb104ae24cf906c93b7fa008d273f235
+Z 4b0826cf6fb92296cc5aa9f45d953141

manifest.uuid

@@ -1 +1 @@
-347df3c1fd7322e7aacaf1e9f8be81830947c482
+8e5cfb2039126da7689c4b1c88760f10e1234eaf

src/btree.c

@@ -5091,10 +5091,22 @@ int sqlite3BtreeMovetoUnpacked(
       *pRes = 0;
       return SQLITE_OK;
     }
-    if( (pCur->curFlags & BTCF_AtLast)!=0 && pCur->info.nKey<intKey ){
+    if( pCur->info.nKey<intKey ){
+      if( (pCur->curFlags & BTCF_AtLast)!=0 ){
         *pRes = -1;
         return SQLITE_OK;
       }
+      if( pCur->aiIdx[pCur->iPage]+1<pCur->apPage[pCur->iPage]->nCell ){
+        pCur->aiIdx[pCur->iPage]++;
+        pCur->info.nSize = 0;
+        pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+        getCellInfo(pCur);
+        if( pCur->info.nKey==intKey ){
+          *pRes = 0;
+          return SQLITE_OK;
+        }
+      }
+    }
   }
 
   if( pIdxKey ){