Fix a performance regression caused by the previous check-in.

FossilOrigin-Name: d7d98d3dff2f0e0cfa5bb8be8e5fd2af5ab470be399eafe3d77b23ee1262f70d

manifest

@@ -1,5 +1,5 @@
-C Add\san\s"||\sCORRUPT_DB"\sterm\sto\san\sassert()\sstatement\sinside\sof\sbtree.
-D 2020-01-07T13:32:15.559
+C Fix\sa\sperformance\sregression\scaused\sby\sthe\sprevious\scheck-in.
+D 2020-01-07T18:10:01.628
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -469,7 +469,7 @@ F src/auth.c a3d5bfdba83d25abed1013a8c7a5f204e2e29b0c25242a56bc02bb0c07bf1e06
 F src/backup.c f70077d40c08b7787bfe934e4d1da8030cb0cc57d46b345fba2294b7d1be23ab
 F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
 F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
-F src/btree.c 68dc49062f5ee261b971157e8db2ca4e290555c872c978eadc1b5441a9c58360
+F src/btree.c d70000b51523138582663b578b7f8a13e5d03c73c7c7ef18fdeafe1c234bbc3c
 F src/btree.h 6111552f19ed7a40f029cf4b33badc6fef9880314fffd80a945f0b7f43ab7471
 F src/btreeInt.h 6794084fad08c9750b45145743c0e3e5c27c94dee89f26dd8df7073314934fd2
 F src/build.c 67b1a8d3ac700747687dbdc49ded847a3c17fef450a8c919ac0399b44cbd4215
@@ -1853,7 +1853,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e1f12978b53683114ab0ef0e84a14dd4fabc72750b214aac19cd9da22a582a27
-R 07b7096e26b431d07883fc9cbfc33796
+P 03c1d75ddc063469fc856114595bd12d21759fe0979ce1ba1cf52e48e6b0d4a1
+R 96e2b728df1be04197061fdf2a9cbc94
 U drh
-Z a639f54f6a0a3a7af89209b4839be8ff
+Z cfff59357eddcd44c962d80542ae3f96

manifest.uuid

@@ -1 +1 @@
-03c1d75ddc063469fc856114595bd12d21759fe0979ce1ba1cf52e48e6b0d4a1
+d7d98d3dff2f0e0cfa5bb8be8e5fd2af5ab470be399eafe3d77b23ee1262f70d

src/btree.c

@@ -2138,11 +2138,11 @@ static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
 */
 static Pgno btreePagecount(BtShared *pBt){
   assert( (pBt->nPage & 0x80000000)==0 || CORRUPT_DB );
-  return pBt->nPage & 0x7fffffff;
+  return pBt->nPage;
 }
 u32 sqlite3BtreeLastPage(Btree *p){
   assert( sqlite3BtreeHoldsMutex(p) );
-  return btreePagecount(p->pBt);
+  return btreePagecount(p->pBt) & 0x7fffffff;
 }
 
 /*