Index: src/pager.c
==================================================================
--- src/pager.c
+++ src/pager.c
@@ -2031,11 +2031,11 @@
 
   sqlite3BitvecDestroy(pPager->pInJournal);
   pPager->pInJournal = 0;
   pPager->nRec = 0;
   if( rc==SQLITE_OK ){
-    if( MEMDB || pagerFlushOnCommit(pPager) ){
+    if( pagerFlushOnCommit(pPager) ){
       sqlite3PcacheCleanAll(pPager->pPCache);
     }else{
       sqlite3PcacheClearWritable(pPager->pPCache);
     }
     sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);

Index: src/pcache.c
==================================================================
--- src/pcache.c
+++ src/pcache.c
@@ -12,11 +12,17 @@
 ** This file implements that page cache.
 */
 #include "sqliteInt.h"
 
 /*
-** A complete page cache is an instance of this structure.
+** A complete page cache is an instance of this structure.  Every
+** entry in the cache holds a single page of the database file.  The
+** btree layer only operates on the cached copy of the database pages.
+**
+** A page cache entry is "clean" if it exactly matches what is currently
+** on disk.  A page is "dirty" if it has been modified and needs to be
+** persisted to disk.
 **
 ** pDirty, pDirtyTail, pSynced:
 **   All dirty pages are linked into the doubly linked list using
 **   PgHdr.pDirtyNext and pDirtyPrev. The list is maintained in LRU order
 **   such that p was added to the list more recently than p->pDirtyNext.

Index: src/pcache.h
==================================================================
--- src/pcache.h
+++ src/pcache.h
@@ -24,11 +24,11 @@
 */
 struct PgHdr {
   sqlite3_pcache_page *pPage;    /* Pcache object page handle */
   void *pData;                   /* Page data */
   void *pExtra;                  /* Extra content */
-  PgHdr *pDirty;                 /* Transient list of dirty pages */
+  PgHdr *pDirty;                 /* Transient list of dirty sorted by pgno */
   Pager *pPager;                 /* The pager this page is part of */
   Pgno pgno;                     /* Page number for this page */
 #ifdef SQLITE_CHECK_PAGES
   u32 pageHash;                  /* Hash of page content */
 #endif