Import SQLite 3.8.7.4.

third_party/sqlite/src/src/pcache.c

 /*
 ** 2008 August 05
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
 **
 **    May you do good and not evil.
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
 ** This file implements that page cache.
 */
 #include "sqliteInt.h"
 
 /*
 ** A complete page cache is an instance of this structure.
 */
 struct PCache {
   PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
   PgHdr *pSynced;                     /* Last synced page in dirty page list */
   int nRef;                           /* Number of referenced pages */
-  int nMax;                           /* Configured cache size */
+  int szCache;                        /* Configured cache size */
   int szPage;                         /* Size of every page in this cache */
   int szExtra;                        /* Size of extra space for each page */
-  int bPurgeable;                     /* True if pages are on backing store */
+  u8 bPurgeable;                      /* True if pages are on backing store */
+  u8 eCreate;                         /* eCreate value for for xFetch() */
   int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
   void *pStress;                      /* Argument to xStress */
   sqlite3_pcache *pCache;             /* Pluggable cache module */
   PgHdr *pPage1;                      /* Reference to page 1 */
 };
 
 /*
 ** Some of the assert() macros in this code are too expensive to run
 ** even during normal debugging.  Use them only rarely on long-running
 ** tests.  Enable the expensive asserts using the
 ** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.
 */
 #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
 # define expensive_assert(X)  assert(X)
 #else
 # define expensive_assert(X)
 #endif
 
 /********************************** Linked List Management ********************/
 
-#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
-/*
-** Check that the pCache->pSynced variable is set correctly. If it
-** is not, either fail an assert or return zero. Otherwise, return
-** non-zero. This is only used in debugging builds, as follows:
-**
-**   expensive_assert( pcacheCheckSynced(pCache) );
-*/
-static int pcacheCheckSynced(PCache *pCache){
-  PgHdr *p;
-  for(p=pCache->pDirtyTail; p!=pCache->pSynced; p=p->pDirtyPrev){
-    assert( p->nRef || (p->flags&PGHDR_NEED_SYNC) );
-  }
-  return (p==0 || p->nRef || (p->flags&PGHDR_NEED_SYNC)==0);
-}
-#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
+/* Allowed values for second argument to pcacheManageDirtyList() */
+#define PCACHE_DIRTYLIST_REMOVE   1    /* Remove pPage from dirty list */
+#define PCACHE_DIRTYLIST_ADD      2    /* Add pPage to the dirty list */
+#define PCACHE_DIRTYLIST_FRONT    3    /* Move pPage to the front of the list */
 
 /*
-** Remove page pPage from the list of dirty pages.
+** Manage pPage's participation on the dirty list.  Bits of the addRemove
+** argument determines what operation to do.  The 0x01 bit means first
+** remove pPage from the dirty list.  The 0x02 means add pPage back to
+** the dirty list.  Doing both moves pPage to the front of the dirty list.
 */
-static void pcacheRemoveFromDirtyList(PgHdr *pPage){
+static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
   PCache *p = pPage->pCache;
 
-  assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
-  assert( pPage->pDirtyPrev || pPage==p->pDirty );
-
-  /* Update the PCache1.pSynced variable if necessary. */
-  if( p->pSynced==pPage ){
-    PgHdr *pSynced = pPage->pDirtyPrev;
-    while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){
-      pSynced = pSynced->pDirtyPrev;
+  if( addRemove & PCACHE_DIRTYLIST_REMOVE ){
+    assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
+    assert( pPage->pDirtyPrev || pPage==p->pDirty );
+  
+    /* Update the PCache1.pSynced variable if necessary. */
+    if( p->pSynced==pPage ){
+      PgHdr *pSynced = pPage->pDirtyPrev;
+      while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){
+        pSynced = pSynced->pDirtyPrev;
+      }
+      p->pSynced = pSynced;
     }
-    p->pSynced = pSynced;
+  
+    if( pPage->pDirtyNext ){
+      pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
+    }else{
+      assert( pPage==p->pDirtyTail );
+      p->pDirtyTail = pPage->pDirtyPrev;
+    }
+    if( pPage->pDirtyPrev ){
+      pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
+    }else{
+      assert( pPage==p->pDirty );
+      p->pDirty = pPage->pDirtyNext;
+      if( p->pDirty==0 && p->bPurgeable ){
+        assert( p->eCreate==1 );
+        p->eCreate = 2;
+      }
+    }
+    pPage->pDirtyNext = 0;
+    pPage->pDirtyPrev = 0;
   }
-
-  if( pPage->pDirtyNext ){
-    pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
-  }else{
-    assert( pPage==p->pDirtyTail );
-    p->pDirtyTail = pPage->pDirtyPrev;
+  if( addRemove & PCACHE_DIRTYLIST_ADD ){
+    assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );
+  
+    pPage->pDirtyNext = p->pDirty;
+    if( pPage->pDirtyNext ){
+      assert( pPage->pDirtyNext->pDirtyPrev==0 );
+      pPage->pDirtyNext->pDirtyPrev = pPage;
+    }else{
+      p->pDirtyTail = pPage;
+      if( p->bPurgeable ){
+        assert( p->eCreate==2 );
+        p->eCreate = 1;
+      }
+    }
+    p->pDirty = pPage;
+    if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
+      p->pSynced = pPage;
+    }
   }
-  if( pPage->pDirtyPrev ){
-    pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
-  }else{
-    assert( pPage==p->pDirty );
-    p->pDirty = pPage->pDirtyNext;
-  }
-  pPage->pDirtyNext = 0;
-  pPage->pDirtyPrev = 0;
-
-  expensive_assert( pcacheCheckSynced(p) );
 }
 
 /*
-** Add page pPage to the head of the dirty list (PCache1.pDirty is set to
-** pPage).
-*/
-static void pcacheAddToDirtyList(PgHdr *pPage){
-  PCache *p = pPage->pCache;
-
-  assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );
-
-  pPage->pDirtyNext = p->pDirty;
-  if( pPage->pDirtyNext ){
-    assert( pPage->pDirtyNext->pDirtyPrev==0 );
-    pPage->pDirtyNext->pDirtyPrev = pPage;
-  }
-  p->pDirty = pPage;
-  if( !p->pDirtyTail ){
-    p->pDirtyTail = pPage;
-  }
-  if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
-    p->pSynced = pPage;
-  }
-  expensive_assert( pcacheCheckSynced(p) );
-}
-
-/*
 ** Wrapper around the pluggable caches xUnpin method. If the cache is
 ** being used for an in-memory database, this function is a no-op.
 */
 static void pcacheUnpin(PgHdr *p){
-  PCache *pCache = p->pCache;
-  if( pCache->bPurgeable ){
+  if( p->pCache->bPurgeable ){
     if( p->pgno==1 ){
-      pCache->pPage1 = 0;
+      p->pCache->pPage1 = 0;
     }
-    sqlite3GlobalConfig.pcache.xUnpin(pCache->pCache, p, 0);
+    sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
   }
 }
 
+/*
+** Compute the number of pages of cache requested.
+*/
+static int numberOfCachePages(PCache *p){
+  if( p->szCache>=0 ){
+    return p->szCache;
+  }else{
+    return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));
+  }
+}
+
 /*************************************************** General Interfaces ******
 **
 ** Initialize and shutdown the page cache subsystem. Neither of these 
 ** functions are threadsafe.
 */
 int sqlite3PcacheInitialize(void){
-  if( sqlite3GlobalConfig.pcache.xInit==0 ){
+  if( sqlite3GlobalConfig.pcache2.xInit==0 ){
     /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
     ** built-in default page cache is used instead of the application defined
     ** page cache. */
     sqlite3PCacheSetDefault();
   }
-  return sqlite3GlobalConfig.pcache.xInit(sqlite3GlobalConfig.pcache.pArg);
+  return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg);
 }
 void sqlite3PcacheShutdown(void){
-  if( sqlite3GlobalConfig.pcache.xShutdown ){
+  if( sqlite3GlobalConfig.pcache2.xShutdown ){
     /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
-    sqlite3GlobalConfig.pcache.xShutdown(sqlite3GlobalConfig.pcache.pArg);
+    sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg);
   }
 }
 
 /*
 ** Return the size in bytes of a PCache object.
 */
 int sqlite3PcacheSize(void){ return sizeof(PCache); }
 
 /*
 ** Create a new PCache object. Storage space to hold the object
 ** has already been allocated and is passed in as the p pointer. 
 ** The caller discovers how much space needs to be allocated by 
 ** calling sqlite3PcacheSize().
 */
-void sqlite3PcacheOpen(
+int sqlite3PcacheOpen(
   int szPage,                  /* Size of every page */
   int szExtra,                 /* Extra space associated with each page */
   int bPurgeable,              /* True if pages are on backing store */
   int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
   void *pStress,               /* Argument to xStress */
   PCache *p                    /* Preallocated space for the PCache */
 ){
   memset(p, 0, sizeof(PCache));
-  p->szPage = szPage;
+  p->szPage = 1;
   p->szExtra = szExtra;
   p->bPurgeable = bPurgeable;
+  p->eCreate = 2;
   p->xStress = xStress;
   p->pStress = pStress;
-  p->nMax = 100;
+  p->szCache = 100;
+  return sqlite3PcacheSetPageSize(p, szPage);
 }
 
 /*
 ** Change the page size for PCache object. The caller must ensure that there
 ** are no outstanding page references when this function is called.
 */
-void sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
+int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
   assert( pCache->nRef==0 && pCache->pDirty==0 );
-  if( pCache->pCache ){
-    sqlite3GlobalConfig.pcache.xDestroy(pCache->pCache);
-    pCache->pCache = 0;
+  if( pCache->szPage ){
+    sqlite3_pcache *pNew;
+    pNew = sqlite3GlobalConfig.pcache2.xCreate(
+                szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable
+    );
+    if( pNew==0 ) return SQLITE_NOMEM;
+    sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache));
+    if( pCache->pCache ){
+      sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
+    }
+    pCache->pCache = pNew;
     pCache->pPage1 = 0;
-  }
-  pCache->szPage = szPage;
+    pCache->szPage = szPage;
+  }
+  return SQLITE_OK;
 }
 
 /*
 ** Try to obtain a page from the cache.
-*/
-int sqlite3PcacheFetch(
+**
+** This routine returns a pointer to an sqlite3_pcache_page object if
+** such an object is already in cache, or if a new one is created.
+** This routine returns a NULL pointer if the object was not in cache
+** and could not be created.
+**
+** The createFlags should be 0 to check for existing pages and should
+** be 3 (not 1, but 3) to try to create a new page.
+**
+** If the createFlag is 0, then NULL is always returned if the page
+** is not already in the cache.  If createFlag is 1, then a new page
+** is created only if that can be done without spilling dirty pages
+** and without exceeding the cache size limit.
+**
+** The caller needs to invoke sqlite3PcacheFetchFinish() to properly
+** initialize the sqlite3_pcache_page object and convert it into a
+** PgHdr object.  The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish()
+** routines are split this way for performance reasons. When separated
+** they can both (usually) operate without having to push values to
+** the stack on entry and pop them back off on exit, which saves a
+** lot of pushing and popping.
+*/
+sqlite3_pcache_page *sqlite3PcacheFetch(
   PCache *pCache,       /* Obtain the page from this cache */
   Pgno pgno,            /* Page number to obtain */
-  int createFlag,       /* If true, create page if it does not exist already */
-  PgHdr **ppPage        /* Write the page here */
-){
-  PgHdr *pPage = 0;
+  int createFlag        /* If true, create page if it does not exist already */
+){
   int eCreate;
 
   assert( pCache!=0 );
-  assert( createFlag==1 || createFlag==0 );
+  assert( pCache->pCache!=0 );
+  assert( createFlag==3 || createFlag==0 );
   assert( pgno>0 );
 
-  /* If the pluggable cache (sqlite3_pcache*) has not been allocated,
-  ** allocate it now.
+  /* eCreate defines what to do if the page does not exist.
+  **    0     Do not allocate a new page.  (createFlag==0)
+  **    1     Allocate a new page if doing so is inexpensive.
+  **          (createFlag==1 AND bPurgeable AND pDirty)
+  **    2     Allocate a new page even it doing so is difficult.
+  **          (createFlag==1 AND !(bPurgeable AND pDirty)
   */
-  if( !pCache->pCache && createFlag ){
-    sqlite3_pcache *p;
-    int nByte;
-    nByte = pCache->szPage + pCache->szExtra + sizeof(PgHdr);
-    p = sqlite3GlobalConfig.pcache.xCreate(nByte, pCache->bPurgeable);
-    if( !p ){
-      return SQLITE_NOMEM;
+  eCreate = createFlag & pCache->eCreate;
+  assert( eCreate==0 || eCreate==1 || eCreate==2 );
+  assert( createFlag==0 || pCache->eCreate==eCreate );
+  assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) );
+  return sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
+}
+
+/*
+** If the sqlite3PcacheFetch() routine is unable to allocate a new
+** page because new clean pages are available for reuse and the cache
+** size limit has been reached, then this routine can be invoked to 
+** try harder to allocate a page.  This routine might invoke the stress
+** callback to spill dirty pages to the journal.  It will then try to
+** allocate the new page and will only fail to allocate a new page on
+** an OOM error.
+**
+** This routine should be invoked only after sqlite3PcacheFetch() fails.
+*/
+int sqlite3PcacheFetchStress(
+  PCache *pCache,                 /* Obtain the page from this cache */
+  Pgno pgno,                      /* Page number to obtain */
+  sqlite3_pcache_page **ppPage    /* Write result here */
+){
+  PgHdr *pPg;
+  if( pCache->eCreate==2 ) return 0;
+
+
+  /* Find a dirty page to write-out and recycle. First try to find a 
+  ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
+  ** cleared), but if that is not possible settle for any other 
+  ** unreferenced dirty page.
+  */
+  for(pPg=pCache->pSynced; 
+      pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
+      pPg=pPg->pDirtyPrev
+  );
+  pCache->pSynced = pPg;
+  if( !pPg ){
+    for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
+  }
+  if( pPg ){
+    int rc;
+#ifdef SQLITE_LOG_CACHE_SPILL
+    sqlite3_log(SQLITE_FULL, 
+                "spill page %d making room for %d - cache used: %d/%d",
+                pPg->pgno, pgno,
+                sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),
+                numberOfCachePages(pCache));
+#endif
+    rc = pCache->xStress(pCache->pStress, pPg);
+    if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+      return rc;
     }
-    sqlite3GlobalConfig.pcache.xCachesize(p, pCache->nMax);
-    pCache->pCache = p;
-  }
-
-  eCreate = createFlag * (1 + (!pCache->bPurgeable || !pCache->pDirty));
-  if( pCache->pCache ){
-    pPage = sqlite3GlobalConfig.pcache.xFetch(pCache->pCache, pgno, eCreate);
-  }
-
-  if( !pPage && eCreate==1 ){
-    PgHdr *pPg;
-
-    /* Find a dirty page to write-out and recycle. First try to find a 
-    ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
-    ** cleared), but if that is not possible settle for any other 
-    ** unreferenced dirty page.
-    */
-    expensive_assert( pcacheCheckSynced(pCache) );
-    for(pPg=pCache->pSynced; 
-        pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
-        pPg=pPg->pDirtyPrev
-    );
-    pCache->pSynced = pPg;
-    if( !pPg ){
-      for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
-    }
-    if( pPg ){
-      int rc;
-      rc = pCache->xStress(pCache->pStress, pPg);
-      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
-        return rc;
-      }
-    }
-
-    pPage = sqlite3GlobalConfig.pcache.xFetch(pCache->pCache, pgno, 2);
-  }
-
-  if( pPage ){
-    if( !pPage->pData ){
-      memset(pPage, 0, sizeof(PgHdr));
-      pPage->pData = (void *)&pPage[1];
-      pPage->pExtra = (void*)&((char *)pPage->pData)[pCache->szPage];
-      memset(pPage->pExtra, 0, pCache->szExtra);
-      pPage->pCache = pCache;
-      pPage->pgno = pgno;
-    }
-    assert( pPage->pCache==pCache );
-    assert( pPage->pgno==pgno );
-    assert( pPage->pData==(void *)&pPage[1] );
-    assert( pPage->pExtra==(void *)&((char *)&pPage[1])[pCache->szPage] );
-
-    if( 0==pPage->nRef ){
-      pCache->nRef++;
-    }
-    pPage->nRef++;
-    if( pgno==1 ){
-      pCache->pPage1 = pPage;
-    }
-  }
-  *ppPage = pPage;
-  return (pPage==0 && eCreate) ? SQLITE_NOMEM : SQLITE_OK;
+  }
+  *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2);
+  return *ppPage==0 ? SQLITE_NOMEM : SQLITE_OK;
+}
+
+/*
+** This is a helper routine for sqlite3PcacheFetchFinish()
+**
+** In the uncommon case where the page being fetched has not been
+** initialized, this routine is invoked to do the initialization.
+** This routine is broken out into a separate function since it
+** requires extra stack manipulation that can be avoided in the common
+** case.
+*/
+static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
+  PCache *pCache,             /* Obtain the page from this cache */
+  Pgno pgno,                  /* Page number obtained */
+  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
+){
+  PgHdr *pPgHdr;
+  assert( pPage!=0 );
+  pPgHdr = (PgHdr*)pPage->pExtra;
+  assert( pPgHdr->pPage==0 );
+ memset(pPgHdr, 0, sizeof(PgHdr));
+  pPgHdr->pPage = pPage;
+  pPgHdr->pData = pPage->pBuf;
+  pPgHdr->pExtra = (void *)&pPgHdr[1];
+  memset(pPgHdr->pExtra, 0, pCache->szExtra);
+  pPgHdr->pCache = pCache;
+  pPgHdr->pgno = pgno;
+  return sqlite3PcacheFetchFinish(pCache,pgno,pPage);
+}
+
+/*
+** This routine converts the sqlite3_pcache_page object returned by
+** sqlite3PcacheFetch() into an initialized PgHdr object.  This routine
+** must be called after sqlite3PcacheFetch() in order to get a usable
+** result.
+*/
+PgHdr *sqlite3PcacheFetchFinish(
+  PCache *pCache,             /* Obtain the page from this cache */
+  Pgno pgno,                  /* Page number obtained */
+  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
+){
+  PgHdr *pPgHdr;
+
+  if( pPage==0 ) return 0;
+  pPgHdr = (PgHdr *)pPage->pExtra;
+
+  if( !pPgHdr->pPage ){
+    return pcacheFetchFinishWithInit(pCache, pgno, pPage);
+  }
+  if( 0==pPgHdr->nRef ){
+    pCache->nRef++;
+  }
+  pPgHdr->nRef++;
+  if( pgno==1 ){
+    pCache->pPage1 = pPgHdr;
+  }
+  return pPgHdr;
 }
 
 /*
 ** Decrement the reference count on a page. If the page is clean and the
-** reference count drops to 0, then it is made elible for recycling.
-*/
-void sqlite3PcacheRelease(PgHdr *p){
+** reference count drops to 0, then it is made eligible for recycling.
+*/
+void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
   assert( p->nRef>0 );
   p->nRef--;
   if( p->nRef==0 ){
-    PCache *pCache = p->pCache;
-    pCache->nRef--;
+    p->pCache->nRef--;
     if( (p->flags&PGHDR_DIRTY)==0 ){
       pcacheUnpin(p);
-    }else{
+    }else if( p->pDirtyPrev!=0 ){
       /* Move the page to the head of the dirty list. */
-      pcacheRemoveFromDirtyList(p);
-      pcacheAddToDirtyList(p);
+      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
     }
   }
 }
 
 /*
 ** Increase the reference count of a supplied page by 1.
 */
 void sqlite3PcacheRef(PgHdr *p){
   assert(p->nRef>0);
   p->nRef++;
 }
 
 /*
 ** Drop a page from the cache. There must be exactly one reference to the
 ** page. This function deletes that reference, so after it returns the
 ** page pointed to by p is invalid.
 */
 void sqlite3PcacheDrop(PgHdr *p){
-  PCache *pCache;
   assert( p->nRef==1 );
   if( p->flags&PGHDR_DIRTY ){
-    pcacheRemoveFromDirtyList(p);
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
   }
-  pCache = p->pCache;
-  pCache->nRef--;
+  p->pCache->nRef--;
   if( p->pgno==1 ){
-    pCache->pPage1 = 0;
+    p->pCache->pPage1 = 0;
   }
-  sqlite3GlobalConfig.pcache.xUnpin(pCache->pCache, p, 1);
+  sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
 }
 
 /*
 ** Make sure the page is marked as dirty. If it isn't dirty already,
 ** make it so.
 */
 void sqlite3PcacheMakeDirty(PgHdr *p){
   p->flags &= ~PGHDR_DONT_WRITE;
   assert( p->nRef>0 );
   if( 0==(p->flags & PGHDR_DIRTY) ){
     p->flags |= PGHDR_DIRTY;
-    pcacheAddToDirtyList( p);
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
   }
 }
 
 /*
 ** Make sure the page is marked as clean. If it isn't clean already,
 ** make it so.
 */
 void sqlite3PcacheMakeClean(PgHdr *p){
   if( (p->flags & PGHDR_DIRTY) ){
-    pcacheRemoveFromDirtyList(p);
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
     p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);
     if( p->nRef==0 ){
       pcacheUnpin(p);
     }
   }
 }
 
 /*
 ** Make every page in the cache clean.
 */
@@ skipping 15 matching lines @@
   pCache->pSynced = pCache->pDirtyTail;
 }
 
 /*
 ** Change the page number of page p to newPgno. 
 */
 void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
   PCache *pCache = p->pCache;
   assert( p->nRef>0 );
   assert( newPgno>0 );
-  sqlite3GlobalConfig.pcache.xRekey(pCache->pCache, p, p->pgno, newPgno);
+  sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);
   p->pgno = newPgno;
   if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){
-    pcacheRemoveFromDirtyList(p);
-    pcacheAddToDirtyList(p);
+    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
   }
 }
 
 /*
 ** Drop every cache entry whose page number is greater than "pgno". The
 ** caller must ensure that there are no outstanding references to any pages
 ** other than page 1 with a page number greater than pgno.
 **
 ** If there is a reference to page 1 and the pgno parameter passed to this
 ** function is 0, then the data area associated with page 1 is zeroed, but
@@ skipping 12 matching lines @@
       assert( p->pgno>0 );
       if( ALWAYS(p->pgno>pgno) ){
         assert( p->flags&PGHDR_DIRTY );
         sqlite3PcacheMakeClean(p);
       }
     }
     if( pgno==0 && pCache->pPage1 ){
       memset(pCache->pPage1->pData, 0, pCache->szPage);
       pgno = 1;
     }
-    sqlite3GlobalConfig.pcache.xTruncate(pCache->pCache, pgno+1);
+    sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
   }
 }
 
 /*
 ** Close a cache.
 */
 void sqlite3PcacheClose(PCache *pCache){
-  if( pCache->pCache ){
-    sqlite3GlobalConfig.pcache.xDestroy(pCache->pCache);
-  }
+  assert( pCache->pCache!=0 );
+  sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
 }
 
 /* 
 ** Discard the contents of the cache.
 */
 void sqlite3PcacheClear(PCache *pCache){
   sqlite3PcacheTruncate(pCache, 0);
 }
 
 /*
@@ skipping 88 matching lines @@
 ** Return the number of references to the page supplied as an argument.
 */
 int sqlite3PcachePageRefcount(PgHdr *p){
   return p->nRef;
 }
 
 /* 
 ** Return the total number of pages in the cache.
 */
 int sqlite3PcachePagecount(PCache *pCache){
-  int nPage = 0;
-  if( pCache->pCache ){
-    nPage = sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache);
-  }
-  return nPage;
+  assert( pCache->pCache!=0 );
+  return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache);
 }
 
 #ifdef SQLITE_TEST
 /*
 ** Get the suggested cache-size value.
 */
 int sqlite3PcacheGetCachesize(PCache *pCache){
-  return pCache->nMax;
+  return numberOfCachePages(pCache);
 }
 #endif
 
 /*
 ** Set the suggested cache-size value.
 */
 void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
-  pCache->nMax = mxPage;
-  if( pCache->pCache ){
-    sqlite3GlobalConfig.pcache.xCachesize(pCache->pCache, mxPage);
-  }
+  assert( pCache->pCache!=0 );
+  pCache->szCache = mxPage;
+  sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,
+                                         numberOfCachePages(pCache));
+}
+
+/*
+** Free up as much memory as possible from the page cache.
+*/
+void sqlite3PcacheShrink(PCache *pCache){
+  assert( pCache->pCache!=0 );
+  sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);
 }
 
 #if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
 /*
 ** For all dirty pages currently in the cache, invoke the specified
 ** callback. This is only used if the SQLITE_CHECK_PAGES macro is
 ** defined.
 */
 void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){
   PgHdr *pDirty;
   for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){
     xIter(pDirty);
   }
 }
 #endif