[sql] Import reference version of SQLite 3.10.2.

third_party/sqlite/sqlite-src-3100200/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 nRefSum;                        /* Sum of ref counts over all pages */
   int szCache;                        /* Configured cache size */
+  int szSpill;                        /* Size before spilling occurs */
   int szPage;                         /* Size of every page in this cache */
   int szExtra;                        /* Size of extra space for each page */
   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 ********************/
 
 /* 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 */
 
 /*
 ** Manage pPage's participation on the dirty list.  Bits of the addRemove
 ** argument determines what operation to do.  The 0x01 bit means first
@@ skipping 55 matching lines @@
     }
   }
 }
 
 /*
 ** 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){
   if( p->pCache->bPurgeable ){
-    if( p->pgno==1 ){
-      p->pCache->pPage1 = 0;
-    }
     sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
   }
 }
 
 /*
-** Compute the number of pages of cache requested.
+** Compute the number of pages of cache requested.   p->szCache is the
+** cache size requested by the "PRAGMA cache_size" statement.
 */
 static int numberOfCachePages(PCache *p){
   if( p->szCache>=0 ){
+    /* IMPLEMENTATION-OF: R-42059-47211 If the argument N is positive then the
+    ** suggested cache size is set to N. */
     return p->szCache;
   }else{
+    /* IMPLEMENTATION-OF: R-61436-13639 If the argument N is negative, then
+    ** the number of cache pages is adjusted to use approximately abs(N*1024)
+    ** bytes of memory. */
     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){
@@ skipping 32 matching lines @@
   PCache *p                    /* Preallocated space for the PCache */
 ){
   memset(p, 0, sizeof(PCache));
   p->szPage = 1;
   p->szExtra = szExtra;
   p->bPurgeable = bPurgeable;
   p->eCreate = 2;
   p->xStress = xStress;
   p->pStress = pStress;
   p->szCache = 100;
+  p->szSpill = 1;
   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.
 */
 int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
-  assert( pCache->nRef==0 && pCache->pDirty==0 );
+  assert( pCache->nRefSum==0 && pCache->pDirty==0 );
   if( pCache->szPage ){
     sqlite3_pcache *pNew;
     pNew = sqlite3GlobalConfig.pcache2.xCreate(
-                szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable
+                szPage, pCache->szExtra + ROUND8(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;
   }
   return SQLITE_OK;
 }
 
 /*
 ** Try to obtain a page from the cache.
 **
 ** 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.
@@ skipping 54 matching lines @@
 ** 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;
+  if( sqlite3PcachePagecount(pCache)>pCache->szSpill ){
+    /* 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),
+      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;
+      rc = pCache->xStress(pCache->pStress, pPg);
+      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
+        return rc;
+      }
     }
   }
   *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));
+  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;
+  pPgHdr->flags = PGHDR_CLEAN;
   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;
+  assert( pPage!=0 );
   pPgHdr = (PgHdr *)pPage->pExtra;
 
   if( !pPgHdr->pPage ){
     return pcacheFetchFinishWithInit(pCache, pgno, pPage);
   }
-  if( 0==pPgHdr->nRef ){
-    pCache->nRef++;
-  }
+  pCache->nRefSum++;
   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 eligible for recycling.
 */
 void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
   assert( p->nRef>0 );
-  p->nRef--;
-  if( p->nRef==0 ){
-    p->pCache->nRef--;
-    if( (p->flags&PGHDR_DIRTY)==0 ){
+  p->pCache->nRefSum--;
+  if( (--p->nRef)==0 ){
+    if( p->flags&PGHDR_CLEAN ){
       pcacheUnpin(p);
     }else if( p->pDirtyPrev!=0 ){
       /* Move the page to the head of the dirty list. */
       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++;
+  p->pCache->nRefSum++;
 }
 
 /*
 ** 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){
   assert( p->nRef==1 );
   if( p->flags&PGHDR_DIRTY ){
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
   }
-  p->pCache->nRef--;
-  if( p->pgno==1 ){
-    p->pCache->pPage1 = 0;
-  }
+  p->pCache->nRefSum--;
   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;
-    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
+  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){
+    p->flags &= ~PGHDR_DONT_WRITE;
+    if( p->flags & PGHDR_CLEAN ){
+      p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN);
+      assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY );
+      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) ){
+    assert( (p->flags & PGHDR_CLEAN)==0 );
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
-    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);
+    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
+    p->flags |= PGHDR_CLEAN;
     if( p->nRef==0 ){
       pcacheUnpin(p);
     }
   }
 }
 
 /*
 ** Make every page in the cache clean.
 */
 void sqlite3PcacheCleanAll(PCache *pCache){
@@ skipping 46 matching lines @@
       /* This routine never gets call with a positive pgno except right
       ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
       ** it must be that pgno==0.
       */
       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;
+    if( pgno==0 && pCache->nRefSum ){
+      sqlite3_pcache_page *pPage1;
+      pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0);
+      if( ALWAYS(pPage1) ){  /* Page 1 is always available in cache, because
+                             ** pCache->nRefSum>0 */
+        memset(pPage1->pBuf, 0, pCache->szPage);
+        pgno = 1;
+      }
     }
     sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
   }
 }
 
 /*
 ** Close a cache.
 */
 void sqlite3PcacheClose(PCache *pCache){
   assert( pCache->pCache!=0 );
@@ skipping 82 matching lines @@
 */
 PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
   PgHdr *p;
   for(p=pCache->pDirty; p; p=p->pDirtyNext){
     p->pDirty = p->pDirtyNext;
   }
   return pcacheSortDirtyList(pCache->pDirty);
 }
 
 /* 
-** Return the total number of referenced pages held by the cache.
+** Return the total number of references to all pages held by the cache.
+**
+** This is not the total number of pages referenced, but the sum of the
+** reference count for all pages.
 */
 int sqlite3PcacheRefCount(PCache *pCache){
-  return pCache->nRef;
+  return pCache->nRefSum;
 }
 
 /*
 ** Return the number of references to the page supplied as an argument.
 */
 int sqlite3PcachePageRefcount(PgHdr *p){
   return p->nRef;
 }
 
 /* 
@@ skipping 17 matching lines @@
 ** Set the suggested cache-size value.
 */
 void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
   assert( pCache->pCache!=0 );
   pCache->szCache = mxPage;
   sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,
                                          numberOfCachePages(pCache));
 }
 
 /*
+** Set the suggested cache-spill value.  Make no changes if if the
+** argument is zero.  Return the effective cache-spill size, which will
+** be the larger of the szSpill and szCache.
+*/
+int sqlite3PcacheSetSpillsize(PCache *p, int mxPage){
+  int res;
+  assert( p->pCache!=0 );
+  if( mxPage ){
+    if( mxPage<0 ){
+      mxPage = (int)((-1024*(i64)mxPage)/(p->szPage+p->szExtra));
+    }
+    p->szSpill = mxPage;
+  }
+  res = numberOfCachePages(p);
+  if( res<p->szSpill ) res = p->szSpill; 
+  return res;
+}
+
+/*
 ** Free up as much memory as possible from the page cache.
 */
 void sqlite3PcacheShrink(PCache *pCache){
   assert( pCache->pCache!=0 );
   sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);
 }
 
+/*
+** Return the size of the header added by this middleware layer
+** in the page-cache hierarchy.
+*/
+int sqlite3HeaderSizePcache(void){ return ROUND8(sizeof(PgHdr)); }
+
+
 #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