diff --git a/manifest b/manifest
index 31fa7b6e12..c7a8d6a401 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Code\ssimplifications\sand\scomment\simprovements\sin\ssupport\sof\sstructural\ncoverage\stesting.\s(CVS\s6899)
-D 2009-07-16T18:21:18
+C Code\ssimplifications\sin\ssupport\sof\sstructural\stesting.\s(CVS\s6900)
+D 2009-07-17T11:44:07
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -105,7 +105,7 @@ F src/attach.c 13995348fc5a26cdd136a50806faf292aabc173f
 F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c 0ef0651714728055d43de7a4cdd95e703fac0119
-F src/btmutex.c 9b899c0d8df3bd68f527b0afe03088321b696d3c
+F src/btmutex.c f7b059a9b08e1af2dd222bf3cc5c45054af0bba6
 F src/btree.c 4d964398d7291fd536cd6361c70ccad9c8dc3b9a
 F src/btree.h e53a10fd31d16c60a86f03c9467a6f470aa3683b
 F src/btreeInt.h 1c86297e69380f6577e7ae67452597dd8d5c2705
@@ -127,7 +127,7 @@ F src/legacy.c 54a11649f27ae55f4fcd6e6b5ba836f839cb8704
 F src/lempar.c 0c4d1ab0a5ef2b0381eb81a732c54f68f27a574d
 F src/loadext.c 0e88a335665db0b2fb4cece3e49dcb65d832635a
 F src/main.c 4e6d1c2418983cebed436be2996a067f9e1bfe5d
-F src/malloc.c 70d226282bc6e1eaccb7e2f6872c69ac31f14c94
+F src/malloc.c 561710bf4b84084e2d047584ab3e7c7094e22a56
 F src/mem0.c f2f84062d1f35814d6535c9f9e33de3bfb3b132c
 F src/mem1.c e6d5c23941288df8191b8a98c28e3f57771e2270
 F src/mem2.c d02bd6a5b34f2d59012a852615621939d9c09548
@@ -152,7 +152,7 @@ F src/pager.h 5aec418bf99f568b92ae82816a1463400513726d
 F src/parse.y bcd46d43fbd23a22b8c020a3eb1806b794794ed5
 F src/pcache.c 7d27635a4bd03c81ce848cb186fea6192706fa1a
 F src/pcache.h 9b927ccc5a538e31b4c3bc7eec4f976db42a1324
-F src/pcache1.c daa2a58a42a3891a5fc1003fad0a704f465eb3b8
+F src/pcache1.c 6dc833c89feac405dd8b4858232c97e679f182ec
 F src/pragma.c 9eb44ac1d3dc1ac3ea4f444abe1a10ae8acaa16c
 F src/prepare.c 12e556fc9f72a6563db7099697f657d75d4bb91c
 F src/printf.c 508a1c59433353552b6553cba175eaa7331f8fc1
@@ -740,7 +740,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P 17c05aefd6c9e938a4cc5d3de348d8c8fdc9394d
-R eacf63252667dbb069131e999be4c4b5
+P 945251798144110787b197f9eb552a2dd4a25cb4
+R 1c8ff9295bcd8f6ec0b813abe7f11af7
 U drh
-Z 929c4cc923822b5a2b9ba3adb55fe10b
+Z a07afaca9e6c4c7b333f6347b1d75539
diff --git a/manifest.uuid b/manifest.uuid
index ccb23ba151..b591ff3a09 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-945251798144110787b197f9eb552a2dd4a25cb4
\ No newline at end of file
+fb1b955dda5105025ef199880afa871e44331d65
\ No newline at end of file
diff --git a/src/btmutex.c b/src/btmutex.c
index 34399bb1fc..ecc2659cb5 100644
--- a/src/btmutex.c
+++ b/src/btmutex.c
@@ -10,7 +10,7 @@
 **
 *************************************************************************
 **
-** $Id: btmutex.c,v 1.15 2009/04/10 12:55:17 danielk1977 Exp $
+** $Id: btmutex.c,v 1.16 2009/07/17 11:44:07 drh Exp $
 **
 ** This file contains code used to implement mutexes on Btree objects.
 ** This code really belongs in btree.c.  But btree.c is getting too
@@ -308,8 +308,12 @@ void sqlite3BtreeMutexArrayEnter(BtreeMutexArray *pArray){
     /* We should already hold a lock on the database connection */
     assert( sqlite3_mutex_held(p->db->mutex) );
 
+    /* The Btree is sharable because only sharable Btrees are entered
+    ** into the array in the first place. */
+    assert( p->sharable );
+
     p->wantToLock++;
-    if( !p->locked && p->sharable ){
+    if( !p->locked ){
       lockBtreeMutex(p);
     }
   }
@@ -324,14 +328,14 @@ void sqlite3BtreeMutexArrayLeave(BtreeMutexArray *pArray){
     Btree *p = pArray->aBtree[i];
     /* Some basic sanity checking */
     assert( i==0 || pArray->aBtree[i-1]->pBt<p->pBt );
-    assert( p->locked || !p->sharable );
+    assert( p->locked );
     assert( p->wantToLock>0 );
 
     /* We should already hold a lock on the database connection */
     assert( sqlite3_mutex_held(p->db->mutex) );
 
     p->wantToLock--;
-    if( p->wantToLock==0 && p->locked ){
+    if( p->wantToLock==0 ){
       unlockBtreeMutex(p);
     }
   }
diff --git a/src/malloc.c b/src/malloc.c
index 9986f377d8..be9093de5e 100644
--- a/src/malloc.c
+++ b/src/malloc.c
@@ -12,7 +12,7 @@
 **
 ** Memory allocation functions used throughout sqlite.
 **
-** $Id: malloc.c,v 1.65 2009/07/16 18:21:18 drh Exp $
+** $Id: malloc.c,v 1.66 2009/07/17 11:44:07 drh Exp $
 */
 #include "sqliteInt.h"
 #include <stdarg.h>
@@ -423,9 +423,7 @@ int sqlite3MallocSize(void *p){
 }
 int sqlite3DbMallocSize(sqlite3 *db, void *p){
   assert( db==0 || sqlite3_mutex_held(db->mutex) );
-  if( p==0 ){
-    return 0;
-  }else if( isLookaside(db, p) ){
+  if( isLookaside(db, p) ){
     return db->lookaside.sz;
   }else{
     return sqlite3GlobalConfig.m.xSize(p);
diff --git a/src/pcache1.c b/src/pcache1.c
index c02e166335..2bb72bc1bd 100644
--- a/src/pcache1.c
+++ b/src/pcache1.c
@@ -16,7 +16,7 @@
 ** If the default page cache implementation is overriden, then neither of
 ** these two features are available.
 **
-** @(#) $Id: pcache1.c,v 1.18 2009/07/16 18:21:18 drh Exp $
+** @(#) $Id: pcache1.c,v 1.19 2009/07/17 11:44:07 drh Exp $
 */
 
 #include "sqliteInt.h"
@@ -218,9 +218,13 @@ static PgHdr1 *pcache1AllocPage(PCache1 *pCache){
 
 /*
 ** Free a page object allocated by pcache1AllocPage().
+**
+** The pointer is allowed to be NULL, which is prudent.  But it turns out
+** that the current implementation happens to never call this routine
+** with a NULL pointer, so we mark the NULL test with ALWAYS().
 */
 static void pcache1FreePage(PgHdr1 *p){
-  if( p ){
+  if( ALWAYS(p) ){
     if( p->pCache->bPurgeable ){
       pcache1.nCurrentPage--;
     }
@@ -471,7 +475,14 @@ static int pcache1Pagecount(sqlite3_pcache *p){
 ** Fetch a page by key value.
 **
 ** Whether or not a new page may be allocated by this function depends on
-** the value of the createFlag argument.
+** the value of the createFlag argument.  0 means do not allocate a new
+** page.  1 means allocate a new page if space is easily available.  2 
+** means to try really hard to allocate a new page.
+**
+** For a non-purgeable cache (a cache used as the storage for an in-memory
+** database) there is really no difference between createFlag 1 and 2.  So
+** the calling function (pcache.c) will never have a createFlag of 1 on
+** a non-purgable cache.
 **
 ** There are three different approaches to obtaining space for a page,
 ** depending on the value of parameter createFlag (which may be 0, 1 or 2).
@@ -482,9 +493,8 @@ static int pcache1Pagecount(sqlite3_pcache *p){
 **   2. If createFlag==0 and the page is not already in the cache, NULL is
 **      returned.
 **
-**   3. If createFlag is 1, the cache is marked as purgeable and the page is 
-**      not already in the cache, and if either of the following are true, 
-**      return NULL:
+**   3. If createFlag is 1, and the page is not already in the cache,
+**      and if either of the following are true, return NULL:
 **
 **       (a) the number of pages pinned by the cache is greater than
 **           PCache1.nMax, or
@@ -513,6 +523,7 @@ static void *pcache1Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){
   PCache1 *pCache = (PCache1 *)p;
   PgHdr1 *pPage = 0;
 
+  assert( pCache->bPurgeable || createFlag!=1 );
   pcache1EnterMutex();
   if( createFlag==1 ) sqlite3BeginBenignMalloc();
 
@@ -529,7 +540,7 @@ static void *pcache1Fetch(sqlite3_pcache *p, unsigned int iKey, int createFlag){
 
   /* Step 3 of header comment. */
   nPinned = pCache->nPage - pCache->nRecyclable;
-  if( createFlag==1 && pCache->bPurgeable && (
+  if( createFlag==1 && (
         nPinned>=(pcache1.nMaxPage+pCache->nMin-pcache1.nMinPage)
      || nPinned>=(pCache->nMax * 9 / 10)
   )){