diff --git a/manifest b/manifest
index 90ad483ca7..bfe61c9805 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Merge\sthe\stest\scase\sfor\sdbsqlfuzz\s18fe4e257be7fa3ecfb0424ab7427e41e97ef9e3\nassertion\sfault,\swhich\sis\sfixed\swith\sthe\sprevious\scheck-in.
-D 2022-08-20T19:45:41.430
+C Add\sthe\snew\sinternal\sinterface\ssqlite3DbNNFreeNN(db,ptr)\swhere\sboth\sthe\ndb\sand\sptr\sparameters\sare\sguaranteed\sto\sbe\snon-NULL.\s\sUse\sthis\swhere\nappropriate\sto\ssave\smore\sthan\s2\smillion\sCPU\scycles\son\sthe\sstandard\nperformance\stest.
+D 2022-08-22T02:00:26.214
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -527,33 +527,33 @@ F src/attach.c 4431f82f0247bf3aaf91589acafdff77d1882235c95407b36da1585c765fbbc8
 F src/auth.c f4fa91b6a90bbc8e0d0f738aa284551739c9543a367071f55574681e0f24f8cf
 F src/backup.c a2891172438e385fdbe97c11c9745676bec54f518d4447090af97189fd8e52d7
 F src/bitvec.c 7c849aac407230278445cb069bebc5f89bf2ddd87c5ed9459b070a9175707b3d
-F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
+F src/btmutex.c 6ffb0a22c19e2f9110be0964d0731d2ef1c67b5f7fabfbaeb7b9dabc4b7740ca
 F src/btree.c 4a8d349b9ed4dc6d252c535227699d75319b633058a56432ebf43c9f56f9085e
 F src/btree.h 74d64b8f28cfa4a894d14d4ed64fa432cd697b98b61708d4351482ae15913e22
 F src/btreeInt.h 8ce1332edd89dfd2461d561ac10a0ab5601c8e06200cb5230596c3caaf54482e
-F src/build.c 1e96f35d5912a1606c9c9463dfd8eaffc76b2bc01207ee372cb3249eef5173c4
-F src/callback.c 4c19af69835787bfe790ac560f3071a824eb629f34e41f97b52ce5235c77de1c
+F src/build.c 898884afd67d953808cb687babc15b66a10213f99fe2ce7db98960e959881f98
+F src/callback.c 4cd7225b26a97f7de5fee5ae10464bed5a78f2adefe19534cc2095b3a8ca484a
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 93e4b5f4faf6d3f688988a116773259a4fbfb4ddac0e9bf9d0ae0429390c2543
 F src/date.c 94ce83b4cd848a387680a5f920c9018c16655db778c4d36525af0a0f34679ac5
 F src/dbpage.c 5808e91bc27fa3981b028000f8fadfdc10ce9e59a34ce7dc4e035a69be3906ec
 F src/dbstat.c 861e08690fcb0f2ee1165eff0060ea8d4f3e2ea10f80dab7d32ad70443a6ff2d
-F src/delete.c cba80ff7370f9d49e147470ef15f05cf00359f0725256a3703b422b6f376e270
-F src/expr.c 0f72468b64eef40c280fd6b273c19f3b221444b00f535c7ba6f34faa657e63da
+F src/delete.c 86573edae75e3d3e9a8b590d87db8e47222103029df4f3e11fa56044459b514e
+F src/expr.c 24e828db6b2fab8aabfb5d2c0d83dbdfc5a1972b1147fa893350e317ab7e282f
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
-F src/fkey.c d965ede15d8360c09ed59348940649ee647b192e784466837d7aefa836d1d91e
+F src/fkey.c 722f20779f5342a787922deded3628d8c74b5249cab04098cf17ee2f2aaff002
 F src/func.c 8f72e88cccdee22185133c10f96ccd61dc34c5ea4b1fa9a73c237ef59b2e64f1
 F src/global.c e83ee571b79ee3adc32e380cf554cf1254bc43763d23786c71721fbcdfbbb965
 F src/hash.c 8d7dda241d0ebdafb6ffdeda3149a412d7df75102cecfc1021c98d6219823b19
 F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
 F src/hwtime.h cb1d7e3e1ed94b7aa6fde95ae2c2daccc3df826be26fc9ed7fd90d1750ae6144
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
-F src/insert.c a8c994e3c3b8b08f61745bedabdf5affc79584a2b3c80ee2e4f038817838bd0a
+F src/insert.c aea5361767817f917b0f0f647a1f0b1621bd858938ae6ae545c3b6b9814b798f
 F src/json.c 7749b98c62f691697c7ee536b570c744c0583cab4a89200fdd0fc2aa8cc8cbd6
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 853385cc7a604157e137585097949252d5d0c731768e16b044608e5c95c3614b
 F src/main.c b91c7e71af6f33640c35b8239a285040aad8dfcfdaaf979152e743c0f8017ea8
-F src/malloc.c 4a3785323104678a8b4b0a482fe0c2a80900e7468ddf76ab0f2ea1c79a8ca8cd
+F src/malloc.c 24369414a0fa402451cec0f0d1e94b637ce8e93c93cd29038ffe7629a8780ebf
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c c12a42539b1ba105e3707d0e628ad70e611040d8f5e38cf942cee30c867083de
 F src/mem2.c c8bfc9446fd0798bddd495eb5d9dbafa7d4b7287d8c22d50a83ac9daa26d8a75
@@ -583,17 +583,17 @@ F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
 F src/pcache1.c 0b4245cd4964e635f2630908c2533cd8e9da7af3ca592e23ae8730aa25ae5eb9
 F src/pragma.c b57a859a366472131194a9ad35cd76d5920577226b04c884b1b9085605faa280
 F src/pragma.h e690a356c18e98414d2e870ea791c1be1545a714ba623719deb63f7f226d8bb7
-F src/prepare.c c62820c15dcb63013519c8e41d9f928d7478672cc902cfd0581c733c271dbf45
+F src/prepare.c 971d5819a4bda88038c2283d71fc0a2974ffc3dd480f9bd941341017abacfd1b
 F src/printf.c e99ee9741e79ae3873458146f59644276657340385ade4e76a5f5d1c25793764
 F src/random.c 546d6feb15ec69c1aafe9bb351a277cbb498fd5410e646add673acb805714960
 F src/resolve.c efea4e5fbecfd6d0a9071b0be0d952620991673391b6ffaaf4c277b0bb674633
 F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
-F src/select.c 4750fbe9d8ecb7236baf7a9bea4299bb87126e08c209645666a0ae8f0efbe0fc
+F src/select.c ccce37e7fbe71089cf6aec91e7134c9c0c1d4840cff9f02587bbc71240d914a5
 F src/shell.c.in 269f682249c1bce2962883e5b99c8702b16a488a43b9ae186daa178713a93c5d
 F src/sqlite.h.in b9b7fd73239d94db20332bb6e504688001e5564b655e1318a4427a1caef4b99e
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a988810c9b21c0dc36dc7a62735012339dc76fc7ab448fb0792721d30eacb69d
-F src/sqliteInt.h 3ae1d20f579149c18ddd995bbeffabf036cad9f4359dc2f27dc1b778d108ff35
+F src/sqliteInt.h 51ccf8da51d5263a21543631f0c3bdca06e9fbe8238a1b2c8d7ba4f4cd118aea
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 4a3da6d77eeb3531cb0dbdf7047772a2a1b99f98c69e90ce009c75fe6328b2c0
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -652,7 +652,7 @@ F src/test_windirent.h 90dfbe95442c9762357fe128dc7ae3dc199d006de93eb33ba3972e0a9
 F src/test_window.c cdae419fdcea5bad6dcd9368c685abdad6deb59e9fc8b84b153de513d394ba3f
 F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
-F src/tokenize.c 36eb0799e487759bbe73e5742b82ee676f06cea2515ff578d03c59a74ccf2d6c
+F src/tokenize.c 1305797eab3542a0896b552c6e7669c972c1468e11e92b370533c1f37a37082b
 F src/treeview.c 07787f67cd297a6d09d04b8d70c06769c60c9c1d9080378f93929c16f8fd3298
 F src/trigger.c 61bea163b1fa3039bc572ed8312461b978e5c527e5301f302b078f4c1ccdec6a
 F src/update.c c52a7991bece0453d22c77c08469512ee2f1391c12503fd347d1c939220c5877
@@ -664,20 +664,20 @@ F src/vdbe.c 4e57ac969bb2252598024ee3ebcb0885cb7976f1606e2bd77975a506da93ed50
 F src/vdbe.h 64619af62603dc3c4f5ff6ff6d2c8f389abd667a29ce6007ed44bd22b3211cd0
 F src/vdbeInt.h 2cad0aeeb106371ed0e0946bab89f60627087068847afc2451c05056961c18da
 F src/vdbeapi.c 4cfbf7ec3ed60366a38655f3f10316c5a3d68f6d4d06e462f88679392611c756
-F src/vdbeaux.c 8584f4a20997fd918f0d957ab4f73d7411159772297c5020c188973bdc41dbf0
+F src/vdbeaux.c cd9fc2fb24755366b2718f5e9e02103c39804bdc9e630620aaec08bb3093c46c
 F src/vdbeblob.c 5e61ce31aca17db8fb60395407457a8c1c7fb471dde405e0cd675974611dcfcd
 F src/vdbemem.c c3ce80af15e2ff5c2824a8db881681cbf511376f13613da020bac6d320c535b1
 F src/vdbesort.c 43756031ca7430f7aec3ef904824a7883c4ede783e51f280d99b9b65c0796e35
 F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1945f1d2e6be5927ec12c06d89b03ef2a4def34bf823
 F src/vdbevtab.c f99b275366c5fc5e2d99f734729880994ab9500bdafde7fae3b02d562b9d323c
-F src/vtab.c 3d72c780d1ea08906a198e4f033921a658a54590e3ed72c544995d84f3f9464a
+F src/vtab.c bb53f9e2eaeecca07158643dd3d5039cf13b525fe2d267e113b39a36f374556c
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c b9df133a705093da8977da5eb202eaadb844839f1c7297c08d33471f5491843d
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
-F src/where.c 8bfe41220558a03be393d064ef3d942cd1ceaf57cd88a85b6cb59b7dda555202
+F src/where.c 6d1ee6f6bc048406554176eb6146b27ac16ec96cca018848aa0b9836b2b71143
 F src/whereInt.h b48ca529ffe293c18cbfa8326af18a09e39910de66fb3e96ef788c7cbf8ef3a7
-F src/wherecode.c 719a5bb0102711a6ebed8d4385b831a27ce679172f3ae8e9aaec0dc1e415a95a
+F src/wherecode.c 6bb1cf9d0a4e3e04dab0bf0ea4a8d936a0dcc05a7e2207beeda6c61aea6dd341
 F src/whereexpr.c 55a39f42aaf982574fbf52906371a84cceed98a994422198dfd03db4fce4cc46
 F src/window.c 928e215840e2f2d9a2746e018c9643ef42c66c4ab6630ef0df7fa388fa145e86
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@@ -1999,9 +1999,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 9433ea4070f52135be64569057f439e7bdb4b3f425d87167c9ebda50011210c1 8372468bb5d8922cf20b8bbee34cfd6044ceb09c26a4efa79a5e6df2c7c4b730
-R 8a2bc608dd9e0c10d3cc034d5ec85f92
-T +closed 8372468bb5d8922cf20b8bbee34cfd6044ceb09c26a4efa79a5e6df2c7c4b730
+P 2d13ec086e96a5446462ce0f689c40c8196e740cd693f5967bfe9eb961f03463
+R bf88e8a14ba34da9f9b58cc1ee676092
 U drh
-Z 96d7e346000d7bc7e6cdccdd39e9e0b9
+Z 1f007ec3ec70bab2436c890728aeb636
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 5136d0d2e9..1388f09e3f 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-2d13ec086e96a5446462ce0f689c40c8196e740cd693f5967bfe9eb961f03463
\ No newline at end of file
+e5eaa80e81fdf86f2875a912b880272b8d099b82b08e945a7988c5dd0fe9d6b5
\ No newline at end of file
diff --git a/src/btmutex.c b/src/btmutex.c
index 275a93ff21..45745b001d 100644
--- a/src/btmutex.c
+++ b/src/btmutex.c
@@ -252,6 +252,7 @@ int sqlite3BtreeHoldsAllMutexes(sqlite3 *db){
 int sqlite3SchemaMutexHeld(sqlite3 *db, int iDb, Schema *pSchema){
   Btree *p;
   assert( db!=0 );
+  if( db->pVfs==0 && db->nDb==0 ) return 1;
   if( pSchema ) iDb = sqlite3SchemaToIndex(db, pSchema);
   assert( iDb>=0 && iDb<db->nDb );
   if( !sqlite3_mutex_held(db->mutex) ) return 0;
diff --git a/src/build.c b/src/build.c
index e3e79df05d..094cf7d61b 100644
--- a/src/build.c
+++ b/src/build.c
@@ -775,16 +775,17 @@ void sqlite3DeleteColumnNames(sqlite3 *db, Table *pTable){
   int i;
   Column *pCol;
   assert( pTable!=0 );
+  assert( db!=0 );
   if( (pCol = pTable->aCol)!=0 ){
     for(i=0; i<pTable->nCol; i++, pCol++){
       assert( pCol->zCnName==0 || pCol->hName==sqlite3StrIHash(pCol->zCnName) );
       sqlite3DbFree(db, pCol->zCnName);
     }
-    sqlite3DbFree(db, pTable->aCol);
+    sqlite3DbNNFreeNN(db, pTable->aCol);
     if( IsOrdinaryTable(pTable) ){
       sqlite3ExprListDelete(db, pTable->u.tab.pDfltList);
     }
-    if( db==0 || db->pnBytesFreed==0 ){
+    if( db->pnBytesFreed==0 ){
       pTable->aCol = 0;
       pTable->nCol = 0;
       if( IsOrdinaryTable(pTable) ){
@@ -821,7 +822,8 @@ static void SQLITE_NOINLINE deleteTable(sqlite3 *db, Table *pTable){
   ** a Table object that was going to be marked ephemeral. So do not check
   ** that no lookaside memory is used in this case either. */
   int nLookaside = 0;
-  if( db && !db->mallocFailed && (pTable->tabFlags & TF_Ephemeral)==0 ){
+  assert( db!=0 );
+  if( !db->mallocFailed && (pTable->tabFlags & TF_Ephemeral)==0 ){
     nLookaside = sqlite3LookasideUsed(db, 0);
   }
 #endif
@@ -831,7 +833,7 @@ static void SQLITE_NOINLINE deleteTable(sqlite3 *db, Table *pTable){
     pNext = pIndex->pNext;
     assert( pIndex->pSchema==pTable->pSchema
          || (IsVirtual(pTable) && pIndex->idxType!=SQLITE_IDXTYPE_APPDEF) );
-    if( (db==0 || db->pnBytesFreed==0) && !IsVirtual(pTable) ){
+    if( db->pnBytesFreed==0 && !IsVirtual(pTable) ){
       char *zName = pIndex->zName; 
       TESTONLY ( Index *pOld = ) sqlite3HashInsert(
          &pIndex->pSchema->idxHash, zName, 0
@@ -868,8 +870,9 @@ static void SQLITE_NOINLINE deleteTable(sqlite3 *db, Table *pTable){
 }
 void sqlite3DeleteTable(sqlite3 *db, Table *pTable){
   /* Do not delete the table until the reference count reaches zero. */
+  assert( db!=0 );
   if( !pTable ) return;
-  if( ((!db || db->pnBytesFreed==0) && (--pTable->nTabRef)>0) ) return;
+  if( db->pnBytesFreed==0 && (--pTable->nTabRef)>0 ) return;
   deleteTable(db, pTable);
 }
 
@@ -4689,12 +4692,13 @@ IdList *sqlite3IdListAppend(Parse *pParse, IdList *pList, Token *pToken){
 */
 void sqlite3IdListDelete(sqlite3 *db, IdList *pList){
   int i;
+  assert( db!=0 );
   if( pList==0 ) return;
   assert( pList->eU4!=EU4_EXPR ); /* EU4_EXPR mode is not currently used */
   for(i=0; i<pList->nId; i++){
     sqlite3DbFree(db, pList->a[i].zName);
   }
-  sqlite3DbFreeNN(db, pList);
+  sqlite3DbNNFreeNN(db, pList);
 }
 
 /*
@@ -4897,11 +4901,12 @@ void sqlite3SrcListAssignCursors(Parse *pParse, SrcList *pList){
 void sqlite3SrcListDelete(sqlite3 *db, SrcList *pList){
   int i;
   SrcItem *pItem;
+  assert( db!=0 );
   if( pList==0 ) return;
   for(pItem=pList->a, i=0; i<pList->nSrc; i++, pItem++){
-    if( pItem->zDatabase ) sqlite3DbFreeNN(db, pItem->zDatabase);
-    sqlite3DbFree(db, pItem->zName);
-    if( pItem->zAlias ) sqlite3DbFreeNN(db, pItem->zAlias);
+    if( pItem->zDatabase ) sqlite3DbNNFreeNN(db, pItem->zDatabase);
+    if( pItem->zName ) sqlite3DbNNFreeNN(db, pItem->zName);
+    if( pItem->zAlias ) sqlite3DbNNFreeNN(db, pItem->zAlias);
     if( pItem->fg.isIndexedBy ) sqlite3DbFree(db, pItem->u1.zIndexedBy);
     if( pItem->fg.isTabFunc ) sqlite3ExprListDelete(db, pItem->u1.pFuncArg);
     sqlite3DeleteTable(db, pItem->pTab);
@@ -4912,7 +4917,7 @@ void sqlite3SrcListDelete(sqlite3 *db, SrcList *pList){
       sqlite3ExprDelete(db, pItem->u3.pOn);
     }
   }
-  sqlite3DbFreeNN(db, pList);
+  sqlite3DbNNFreeNN(db, pList);
 }
 
 /*
diff --git a/src/callback.c b/src/callback.c
index 7d8f9dcbce..6cbe8e5847 100644
--- a/src/callback.c
+++ b/src/callback.c
@@ -490,19 +490,21 @@ void sqlite3SchemaClear(void *p){
   Hash temp2;
   HashElem *pElem;
   Schema *pSchema = (Schema *)p;
+  sqlite3 xdb;
 
+  memset(&xdb, 0, sizeof(xdb));
   temp1 = pSchema->tblHash;
   temp2 = pSchema->trigHash;
   sqlite3HashInit(&pSchema->trigHash);
   sqlite3HashClear(&pSchema->idxHash);
   for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
-    sqlite3DeleteTrigger(0, (Trigger*)sqliteHashData(pElem));
+    sqlite3DeleteTrigger(&xdb, (Trigger*)sqliteHashData(pElem));
   }
   sqlite3HashClear(&temp2);
   sqlite3HashInit(&pSchema->tblHash);
   for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){
     Table *pTab = sqliteHashData(pElem);
-    sqlite3DeleteTable(0, pTab);
+    sqlite3DeleteTable(&xdb, pTab);
   }
   sqlite3HashClear(&temp1);
   sqlite3HashClear(&pSchema->fkeyHash);
diff --git a/src/delete.c b/src/delete.c
index 056d6f3bef..704a3c7110 100644
--- a/src/delete.c
+++ b/src/delete.c
@@ -676,7 +676,7 @@ delete_from_cleanup:
   sqlite3ExprListDelete(db, pOrderBy);
   sqlite3ExprDelete(db, pLimit);
 #endif
-  sqlite3DbFree(db, aToOpen);
+  if( aToOpen ) sqlite3DbNNFreeNN(db, aToOpen);
   return;
 }
 /* Make sure "isView" and other macros defined above are undefined. Otherwise
diff --git a/src/expr.c b/src/expr.c
index be3e73294f..8572512926 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1220,6 +1220,7 @@ void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr, u32 n){
 */
 static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){
   assert( p!=0 );
+  assert( db!=0 );
   assert( !ExprUseUValue(p) || p->u.iValue>=0 );
   assert( !ExprUseYWin(p) || !ExprUseYSub(p) );
   assert( !ExprUseYWin(p) || p->y.pWin!=0 || db->mallocFailed );
@@ -1252,7 +1253,7 @@ static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){
     }
   }
   if( !ExprHasProperty(p, EP_Static) ){
-    sqlite3DbFreeNN(db, p);
+    sqlite3DbNNFreeNN(db, p);
   }
 }
 void sqlite3ExprDelete(sqlite3 *db, Expr *p){
@@ -2038,12 +2039,13 @@ static SQLITE_NOINLINE void exprListDeleteNN(sqlite3 *db, ExprList *pList){
   int i = pList->nExpr;
   struct ExprList_item *pItem =  pList->a;
   assert( pList->nExpr>0 );
+  assert( db!=0 );
   do{
     sqlite3ExprDelete(db, pItem->pExpr);
-    sqlite3DbFree(db, pItem->zEName);
+    if( pItem->zEName ) sqlite3DbNNFreeNN(db, pItem->zEName);
     pItem++;
   }while( --i>0 );
-  sqlite3DbFreeNN(db, pList);
+  sqlite3DbNNFreeNN(db, pList);
 }
 void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
   if( pList ) exprListDeleteNN(db, pList);
@@ -6075,6 +6077,7 @@ static int exprRefToSrcList(Walker *pWalker, Expr *pExpr){
 int sqlite3ReferencesSrcList(Parse *pParse, Expr *pExpr, SrcList *pSrcList){
   Walker w;
   struct RefSrcList x;
+  assert( pParse->db!=0 );
   memset(&w, 0, sizeof(w));
   memset(&x, 0, sizeof(x));
   w.xExprCallback = exprRefToSrcList;
@@ -6091,7 +6094,7 @@ int sqlite3ReferencesSrcList(Parse *pParse, Expr *pExpr, SrcList *pSrcList){
     sqlite3WalkExpr(&w, pExpr->y.pWin->pFilter);
   }
 #endif
-  sqlite3DbFree(pParse->db, x.aiExclude);
+  if( x.aiExclude ) sqlite3DbNNFreeNN(pParse->db, x.aiExclude);
   if( w.eCode & 0x01 ){
     return 1;
   }else if( w.eCode ){
diff --git a/src/fkey.c b/src/fkey.c
index a057925145..cae6bb19d3 100644
--- a/src/fkey.c
+++ b/src/fkey.c
@@ -1439,11 +1439,12 @@ void sqlite3FkDelete(sqlite3 *db, Table *pTab){
   FKey *pNext;                    /* Copy of pFKey->pNextFrom */
 
   assert( IsOrdinaryTable(pTab) );
+  assert( db!=0 );
   for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pNext){
     assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
 
     /* Remove the FK from the fkeyHash hash table. */
-    if( !db || db->pnBytesFreed==0 ){
+    if( db->pnBytesFreed==0 ){
       if( pFKey->pPrevTo ){
         pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
       }else{
diff --git a/src/insert.c b/src/insert.c
index 6de304848e..6c71391a1b 100644
--- a/src/insert.c
+++ b/src/insert.c
@@ -1417,7 +1417,7 @@ insert_cleanup:
   sqlite3UpsertDelete(db, pUpsert);
   sqlite3SelectDelete(db, pSelect);
   sqlite3IdListDelete(db, pColumn);
-  sqlite3DbFree(db, aRegIdx);
+  if( aRegIdx ) sqlite3DbNNFreeNN(db, aRegIdx);
 }
 
 /* Make sure "isView" and other macros defined above are undefined. Otherwise
diff --git a/src/malloc.c b/src/malloc.c
index c508bf752c..d0ed48dba1 100644
--- a/src/malloc.c
+++ b/src/malloc.c
@@ -441,6 +441,41 @@ void sqlite3DbFreeNN(sqlite3 *db, void *p){
   sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
   sqlite3_free(p);
 }
+void sqlite3DbNNFreeNN(sqlite3 *db, void *p){
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  assert( p!=0 );
+  if( db->pnBytesFreed ){
+    measureAllocationSize(db, p);
+    return;
+  }
+  if( ((uptr)p)<(uptr)(db->lookaside.pEnd) ){
+#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE
+    if( ((uptr)p)>=(uptr)(db->lookaside.pMiddle) ){
+      LookasideSlot *pBuf = (LookasideSlot*)p;
+#ifdef SQLITE_DEBUG
+      memset(p, 0xaa, LOOKASIDE_SMALL);  /* Trash freed content */
+#endif
+      pBuf->pNext = db->lookaside.pSmallFree;
+      db->lookaside.pSmallFree = pBuf;
+      return;
+    }
+#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */
+    if( ((uptr)p)>=(uptr)(db->lookaside.pStart) ){
+      LookasideSlot *pBuf = (LookasideSlot*)p;
+#ifdef SQLITE_DEBUG
+      memset(p, 0xaa, db->lookaside.szTrue);  /* Trash freed content */
+#endif
+      pBuf->pNext = db->lookaside.pFree;
+      db->lookaside.pFree = pBuf;
+      return;
+    }
+  }
+  assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
+  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+  sqlite3_free(p);
+}
 void sqlite3DbFree(sqlite3 *db, void *p){
   assert( db==0 || sqlite3_mutex_held(db->mutex) );
   if( p ) sqlite3DbFreeNN(db, p);
diff --git a/src/prepare.c b/src/prepare.c
index f55ff72fcb..f66c366b99 100644
--- a/src/prepare.c
+++ b/src/prepare.c
@@ -574,15 +574,15 @@ void sqlite3ParseObjectReset(Parse *pParse){
   assert( db->pParse==pParse );
   assert( pParse->nested==0 );
 #ifndef SQLITE_OMIT_SHARED_CACHE
-  sqlite3DbFree(db, pParse->aTableLock);
+  if( pParse->aTableLock ) sqlite3DbNNFreeNN(db, pParse->aTableLock);
 #endif
   while( pParse->pCleanup ){
     ParseCleanup *pCleanup = pParse->pCleanup;
     pParse->pCleanup = pCleanup->pNext;
     pCleanup->xCleanup(db, pCleanup->pPtr);
-    sqlite3DbFreeNN(db, pCleanup);
+    sqlite3DbNNFreeNN(db, pCleanup);
   }
-  sqlite3DbFree(db, pParse->aLabel);
+  if( pParse->aLabel ) sqlite3DbNNFreeNN(db, pParse->aLabel);
   if( pParse->pConstExpr ){
     sqlite3ExprListDelete(db, pParse->pConstExpr);
   }
diff --git a/src/select.c b/src/select.c
index 3f80e44ce2..39ec70f2b5 100644
--- a/src/select.c
+++ b/src/select.c
@@ -76,6 +76,7 @@ struct SortCtx {
 ** If bFree==0, Leave the first Select object unfreed
 */
 static void clearSelect(sqlite3 *db, Select *p, int bFree){
+  assert( db!=0 );
   while( p ){
     Select *pPrior = p->pPrior;
     sqlite3ExprListDelete(db, p->pEList);
@@ -95,7 +96,7 @@ static void clearSelect(sqlite3 *db, Select *p, int bFree){
       sqlite3WindowUnlinkFromSelect(p->pWin);
     }
 #endif
-    if( bFree ) sqlite3DbFreeNN(db, p);
+    if( bFree ) sqlite3DbNNFreeNN(db, p);
     p = pPrior;
     bFree = 1;
   }
@@ -1501,9 +1502,10 @@ KeyInfo *sqlite3KeyInfoAlloc(sqlite3 *db, int N, int X){
 */
 void sqlite3KeyInfoUnref(KeyInfo *p){
   if( p ){
+    assert( p->db!=0 );
     assert( p->nRef>0 );
     p->nRef--;
-    if( p->nRef==0 ) sqlite3DbFreeNN(p->db, p);
+    if( p->nRef==0 ) sqlite3DbNNFreeNN(p->db, p);
   }
 }
 
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 32e0e78e83..c53b4f3bb9 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -4364,6 +4364,7 @@ void *sqlite3DbReallocOrFree(sqlite3 *, void *, u64);
 void *sqlite3DbRealloc(sqlite3 *, void *, u64);
 void sqlite3DbFree(sqlite3*, void*);
 void sqlite3DbFreeNN(sqlite3*, void*);
+void sqlite3DbNNFreeNN(sqlite3*, void*);
 int sqlite3MallocSize(const void*);
 int sqlite3DbMallocSize(sqlite3*, const void*);
 void *sqlite3PageMalloc(int);
diff --git a/src/tokenize.c b/src/tokenize.c
index b147cdb40f..8dac9ece52 100644
--- a/src/tokenize.c
+++ b/src/tokenize.c
@@ -711,7 +711,7 @@ int sqlite3RunParser(Parse *pParse, const char *zSql){
   if( pParse->pNewTrigger && !IN_RENAME_OBJECT ){
     sqlite3DeleteTrigger(db, pParse->pNewTrigger);
   }
-  if( pParse->pVList ) sqlite3DbFreeNN(db, pParse->pVList);
+  if( pParse->pVList ) sqlite3DbNNFreeNN(db, pParse->pVList);
   db->pParse = pParentParse;
   assert( nErr==0 || pParse->rc!=SQLITE_OK );
   return nErr;
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 8ab7978fa1..ca711d8d0d 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -884,7 +884,7 @@ static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
   }
 resolve_p2_values_loop_exit:
   if( aLabel ){
-    sqlite3DbFreeNN(p->db, pParse->aLabel);
+    sqlite3DbNNFreeNN(p->db, pParse->aLabel);
     pParse->aLabel = 0;
   }
   pParse->nLabel = 0;
@@ -1195,8 +1195,9 @@ void sqlite3VdbeJumpHereOrPopInst(Vdbe *p, int addr){
 ** the FuncDef is not ephermal, then do nothing.
 */
 static void freeEphemeralFunction(sqlite3 *db, FuncDef *pDef){
+  assert( db!=0 );
   if( (pDef->funcFlags & SQLITE_FUNC_EPHEM)!=0 ){
-    sqlite3DbFreeNN(db, pDef);
+    sqlite3DbNNFreeNN(db, pDef);
   }
 }
 
@@ -1205,11 +1206,12 @@ static void freeEphemeralFunction(sqlite3 *db, FuncDef *pDef){
 */
 static SQLITE_NOINLINE void freeP4Mem(sqlite3 *db, Mem *p){
   if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
-  sqlite3DbFreeNN(db, p);
+  sqlite3DbNNFreeNN(db, p);
 }
 static SQLITE_NOINLINE void freeP4FuncCtx(sqlite3 *db, sqlite3_context *p){
+  assert( db!=0 );
   freeEphemeralFunction(db, p->pFunc);
-  sqlite3DbFreeNN(db, p);
+  sqlite3DbNNFreeNN(db, p);
 }
 static void freeP4(sqlite3 *db, int p4type, void *p4){
   assert( db );
@@ -1222,7 +1224,7 @@ static void freeP4(sqlite3 *db, int p4type, void *p4){
     case P4_INT64:
     case P4_DYNAMIC:
     case P4_INTARRAY: {
-      sqlite3DbFree(db, p4);
+      if( p4 ) sqlite3DbNNFreeNN(db, p4);
       break;
     }
     case P4_KEYINFO: {
@@ -1261,6 +1263,7 @@ static void freeP4(sqlite3 *db, int p4type, void *p4){
 */
 static void vdbeFreeOpArray(sqlite3 *db, Op *aOp, int nOp){
   assert( nOp>=0 );
+  assert( db!=0 );
   if( aOp ){
     Op *pOp = &aOp[nOp-1];
     while(1){  /* Exit via break */
@@ -1271,7 +1274,7 @@ static void vdbeFreeOpArray(sqlite3 *db, Op *aOp, int nOp){
       if( pOp==aOp ) break;
       pOp--;
     }
-    sqlite3DbFreeNN(db, aOp);
+    sqlite3DbNNFreeNN(db, aOp);
   }
 }
 
@@ -2025,7 +2028,7 @@ static void releaseMemArray(Mem *p, int N){
         sqlite3VdbeMemRelease(p);
         p->flags = MEM_Undefined;
       }else if( p->szMalloc ){
-        sqlite3DbFreeNN(db, p->zMalloc);
+        sqlite3DbNNFreeNN(db, p->zMalloc);
         p->szMalloc = 0;
         p->flags = MEM_Undefined;
       }
@@ -3546,10 +3549,11 @@ void sqlite3VdbeDeleteAuxData(sqlite3 *db, AuxData **pp, int iOp, int mask){
 */
 static void sqlite3VdbeClearObject(sqlite3 *db, Vdbe *p){
   SubProgram *pSub, *pNext;
+  assert( db!=0 );
   assert( p->db==0 || p->db==db );
   if( p->aColName ){
     releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
-    sqlite3DbFreeNN(db, p->aColName);
+    sqlite3DbNNFreeNN(db, p->aColName);
   }
   for(pSub=p->pProgram; pSub; pSub=pNext){
     pNext = pSub->pNext;
@@ -3558,11 +3562,11 @@ static void sqlite3VdbeClearObject(sqlite3 *db, Vdbe *p){
   }
   if( p->eVdbeState!=VDBE_INIT_STATE ){
     releaseMemArray(p->aVar, p->nVar);
-    if( p->pVList ) sqlite3DbFreeNN(db, p->pVList);
-    if( p->pFree ) sqlite3DbFreeNN(db, p->pFree);
+    if( p->pVList ) sqlite3DbNNFreeNN(db, p->pVList);
+    if( p->pFree ) sqlite3DbNNFreeNN(db, p->pFree);
   }
   vdbeFreeOpArray(db, p->aOp, p->nOp);
-  sqlite3DbFree(db, p->zSql);
+  if( p->zSql ) sqlite3DbNNFreeNN(db, p->zSql);
 #ifdef SQLITE_ENABLE_NORMALIZE
   sqlite3DbFree(db, p->zNormSql);
   {
@@ -3592,6 +3596,7 @@ void sqlite3VdbeDelete(Vdbe *p){
 
   assert( p!=0 );
   db = p->db;
+  assert( db!=0 );
   assert( sqlite3_mutex_held(db->mutex) );
   sqlite3VdbeClearObject(db, p);
   if( db->pnBytesFreed==0 ){
@@ -3605,7 +3610,7 @@ void sqlite3VdbeDelete(Vdbe *p){
       p->pNext->pPrev = p->pPrev;
     }
   }
-  sqlite3DbFreeNN(db, p);
+  sqlite3DbNNFreeNN(db, p);
 }
 
 /*
@@ -5221,13 +5226,14 @@ void sqlite3VtabImportErrmsg(Vdbe *p, sqlite3_vtab *pVtab){
 ** the vdbeUnpackRecord() function found in vdbeapi.c.
 */
 static void vdbeFreeUnpacked(sqlite3 *db, int nField, UnpackedRecord *p){
+  assert( db!=0 );
   if( p ){
     int i;
     for(i=0; i<nField; i++){
       Mem *pMem = &p->aMem[i];
       if( pMem->zMalloc ) sqlite3VdbeMemReleaseMalloc(pMem);
     }
-    sqlite3DbFreeNN(db, p);
+    sqlite3DbNNFreeNN(db, p);
   }
 }
 #endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
@@ -5298,7 +5304,7 @@ void sqlite3VdbePreUpdateHook(
     for(i=0; i<pCsr->nField; i++){
       sqlite3VdbeMemRelease(&preupdate.aNew[i]);
     }
-    sqlite3DbFreeNN(db, preupdate.aNew);
+    sqlite3DbNNFreeNN(db, preupdate.aNew);
   }
 }
 #endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
diff --git a/src/vtab.c b/src/vtab.c
index b50ccd24a6..9bf031faf0 100644
--- a/src/vtab.c
+++ b/src/vtab.c
@@ -340,7 +340,8 @@ void sqlite3VtabUnlockList(sqlite3 *db){
 */
 void sqlite3VtabClear(sqlite3 *db, Table *p){
   assert( IsVirtual(p) );
-  if( !db || db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
+  assert( db!=0 );
+  if( db->pnBytesFreed==0 ) vtabDisconnectAll(0, p);
   if( p->u.vtab.azArg ){
     int i;
     for(i=0; i<p->u.vtab.nArg; i++){
diff --git a/src/where.c b/src/where.c
index 9c4678345e..0a6f5e6273 100644
--- a/src/where.c
+++ b/src/where.c
@@ -2251,8 +2251,9 @@ static int whereLoopXfer(sqlite3 *db, WhereLoop *pTo, WhereLoop *pFrom){
 ** Delete a WhereLoop object
 */
 static void whereLoopDelete(sqlite3 *db, WhereLoop *p){
+  assert( db!=0 );
   whereLoopClear(db, p);
-  sqlite3DbFreeNN(db, p);
+  sqlite3DbNNFreeNN(db, p);
 }
 
 /*
@@ -2260,6 +2261,7 @@ static void whereLoopDelete(sqlite3 *db, WhereLoop *p){
 */
 static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
   assert( pWInfo!=0 );
+  assert( db!=0 );
   sqlite3WhereClauseClear(&pWInfo->sWC);
   while( pWInfo->pLoops ){
     WhereLoop *p = pWInfo->pLoops;
@@ -2269,10 +2271,10 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
   assert( pWInfo->pExprMods==0 );
   while( pWInfo->pMemToFree ){
     WhereMemBlock *pNext = pWInfo->pMemToFree->pNext;
-    sqlite3DbFreeNN(db, pWInfo->pMemToFree);
+    sqlite3DbNNFreeNN(db, pWInfo->pMemToFree);
     pWInfo->pMemToFree = pNext;
   }
-  sqlite3DbFreeNN(db, pWInfo);
+  sqlite3DbNNFreeNN(db, pWInfo);
 }
 
 /* Undo all Expr node modifications
@@ -5073,7 +5075,8 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
   pWInfo->nRowOut = pFrom->nRow;
 
   /* Free temporary memory and return success */
-  sqlite3DbFreeNN(db, pSpace);
+  assert( db!=0 );
+  sqlite3DbNNFreeNN(db, pSpace);
   return SQLITE_OK;
 }
 
diff --git a/src/wherecode.c b/src/wherecode.c
index 85df64279c..4c34ea0dc6 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -2109,8 +2109,8 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       }
       nConstraint++;
     }
-    sqlite3DbFree(db, zStartAff);
-    sqlite3DbFree(db, zEndAff);
+    if( zStartAff ) sqlite3DbNNFreeNN(db, zStartAff);
+    if( zEndAff ) sqlite3DbNNFreeNN(db, zEndAff);
 
     /* Top of the loop body */
     if( pLevel->p2==0 ) pLevel->p2 = sqlite3VdbeCurrentAddr(v);