**    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.
**
** @(#) $Id: pcache.c,v 1.26 2008/09/02 09:38:07 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
  int szExtra = pCache->szExtra;

  assert( pcache_g.isInit );
  assert( sqlite3_mutex_held(pcache_g.mutex) );

  *ppPage = 0;

  /* If we have reached the limit for pinned/dirty pages, and there is at
  ** least one dirty page, invoke the xStress callback to cause a page to
  ** become clean.
  */
  expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
  expensive_assert( pcacheCheckSynced(pCache) );
  if( pCache->xStress
   && pCache->pDirty
   && pCache->nPinned>=(pcache_g.nMaxPage+pCache->nMin-pcache_g.nMinPage)

  ){
    PgHdr *pPg;
    assert(pCache->pDirtyTail);

    for(pPg=pCache->pSynced; 
        pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
        pPg=pPg->pPrev
................................................................................
      pcacheEnterMutex();
      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
        return rc;
      }
    }
  }

  /* If the global page limit has been reached, try to recycle a page. */



  if( pCache->bPurgeable && pcache_g.nCurrentPage>=pcache_g.nMaxPage ){
    p = pcacheRecyclePage();
  }

  /* If a page has been recycled but it is the wrong size, free it. */
  if( p && (p->pCache->szPage!=szPage || p->pCache->szPage!=szExtra) ){
    pcachePageFree(p);
    p = 0;
................................................................................

  *pnCurrent = pcache_g.nCurrentPage;
  *pnMax = pcache_g.nMaxPage;
  *pnMin = pcache_g.nMinPage;
  *pnRecyclable = nRecyclable;
}
#endif

**    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.
**
** @(#) $Id: pcache.c,v 1.27 2008/09/15 15:36:58 drh Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
................................................................................
  int szExtra = pCache->szExtra;

  assert( pcache_g.isInit );
  assert( sqlite3_mutex_held(pcache_g.mutex) );

  *ppPage = 0;

  /* If we have reached either the global or the local limit for 
  ** pinned+dirty pages, and there is at least one dirty page,
  ** invoke the xStress callback to cause a page to become clean.
  */
  expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
  expensive_assert( pcacheCheckSynced(pCache) );
  if( pCache->xStress
   && pCache->pDirty
   && (pCache->nPinned>=(pcache_g.nMaxPage+pCache->nMin-pcache_g.nMinPage)
           || pCache->nPinned>=pCache->nMax)
  ){
    PgHdr *pPg;
    assert(pCache->pDirtyTail);

    for(pPg=pCache->pSynced; 
        pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
        pPg=pPg->pPrev
................................................................................
      pcacheEnterMutex();
      if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
        return rc;
      }
    }
  }

  /* If either the local or the global page limit has been reached, 
  ** try to recycle a page. 
  */
  if( pCache->bPurgeable && (pCache->nPage>=pCache->nMax-1 ||
                             pcache_g.nCurrentPage>=pcache_g.nMaxPage) ){
    p = pcacheRecyclePage();
  }

  /* If a page has been recycled but it is the wrong size, free it. */
  if( p && (p->pCache->szPage!=szPage || p->pCache->szPage!=szExtra) ){
    pcachePageFree(p);
    p = 0;
................................................................................

  *pnCurrent = pcache_g.nCurrentPage;
  *pnMax = pcache_g.nMaxPage;
  *pnMin = pcache_g.nMinPage;
  *pnRecyclable = nRecyclable;
}
#endif

# 2008 September 15
#
# 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 is focused on testing the pcache module.
#
# $Id: pcache2.test,v 1.1 2008/09/15 15:36:58 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl


# Set up a pcache memory pool so that we can easily track how many
# pages are being used for cache.
#
do_test pcache2-1.1 {
  db close
  sqlite3_shutdown
  sqlite3_config_pagecache 6000 100
  sqlite3_initialize
  sqlite3_status SQLITE_STATUS_PAGECACHE_USED 1
  sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0
} {0 0 0}

# Open up two database connections to separate files.
#
do_test pcache2-1.2 {
  file delete -force test.db test.db-journal
  sqlite3 db test.db
  db eval {PRAGMA cache_size=10}
  lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 1
} {2}
do_test pcache2-1.3 {
  file delete -force test2.db test2.db-journal
  sqlite3 db2 test2.db
  db2 eval {PRAGMA cache_size=50}
  lindex [sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0] 1
} {4}

# Make lots of changes on the first connection.  Verify that the
# page cache usage does not grow to consume the page space set aside
# for the second connection.
#
do_test pcache2-1.4 {
  db eval {
     CREATE TABLE t1(a,b);
     CREATE TABLE t2(x,y);
     INSERT INTO t1 VALUES(1, zeroblob(800));
     INSERT INTO t1 VALUES(2, zeroblob(800));
     INSERT INTO t2 SELECT * FROM t1;
     INSERT INTO t1 SELECT x+2, y FROM t2;
     INSERT INTO t2 SELECT a+10, b FROM t1;
     INSERT INTO t1 SELECT x+10, y FROM t2;
     INSERT INTO t2 SELECT a+100, b FROM t1;
     INSERT INTO t1 SELECT x+100, y FROM t2;
     INSERT INTO t2 SELECT a+1000, b FROM t1;
     INSERT INTO t1 SELECT x+1000, y FROM t2;
  }
  sqlite3_status SQLITE_STATUS_PAGECACHE_USED 0
} {0 13 13}

catch {db2 close}
finish_test