SQLite

/*
** 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.
**
** @(#) $Id: pcache.c,v 1.24 2008/08/29 09:10:03 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

    if( p->pCache->xDestroy ){
      p->pCache->xDestroy(p);
    }
    pCache->nRef--;
    if( (p->flags&PGHDR_DIRTY)==0 ){
      pCache->nPinned--;
      pcacheEnterMutex();
      if( pcache.nCurrentPage>pcache.nMaxPage ){
        pcacheRemoveFromList(&pCache->pClean, p);
        pcacheRemoveFromHash(p);
        pcachePageFree(p);
      }else{
        pcacheAddToLruList(p);
      }
      pcacheExitMutex();
    }else{
      /* Move the page to the head of the caches dirty list. */
      pcacheRemoveFromList(&pCache->pDirty, p);
      pcacheAddToList(&pCache->pDirty, p);
    }
  }

        memset(p->pData, 0, pCache->szPage);
      }
    }
  }
  pcacheExitMutex();
}

/*
** If there are currently more than pcache.nMaxPage pages allocated, try
** to recycle pages to reduce the number allocated to pcache.nMaxPage.
*/
static void pcacheEnforceMaxPage(){
  PgHdr *p;
  assert( sqlite3_mutex_held(pcache.mutex) );
  while( pcache.nCurrentPage>pcache.nMaxPage && (p = pcacheRecyclePage()) ){
    pcachePageFree(p);
  }
}

/*
** Close a cache.
*/
void sqlite3PcacheClose(PCache *pCache){
  pcacheEnterMutex();

  /* Free all the pages used by this pager and remove them from the LRU list. */
  pcacheClear(pCache);
  if( pCache->bPurgeable ){
    pcache.nMaxPage -= pCache->nMax;
    pcache.nMinPage -= pCache->nMin;
    pcacheEnforceMaxPage();
  }
  sqlite3_free(pCache->apHash);

  pcacheExitMutex();
}

/*
** Preserve the content of the page.  It is assumed that the content
** has not been preserved already.
**

  if( mxPage<10 ){
    mxPage = 10;
  }
  if( pCache->bPurgeable ){
    pcacheEnterMutex();
    pcache.nMaxPage -= pCache->nMax;
    pcache.nMaxPage += mxPage;
    pcacheEnforceMaxPage();
    pcacheExitMutex();
  }
  pCache->nMax = mxPage;
}

#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
/*

      pcachePageFree(p);
    }
    pcacheExitMutex();
  }
  return nFree;
}
#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */

#ifdef SQLITE_TEST
void sqlite3PcacheStats(
  int *pnCurrent,
  int *pnMax,
  int *pnMin,
  int *pnRecyclable
){
  PgHdr *p;
  int nRecyclable = 0;
  for(p=pcache.pLruHead; p; p=p->pNextLru){
    nRecyclable++;
  }

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

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite page cache
** subsystem. 
**
** @(#) $Id: pcache.h,v 1.9 2008/08/29 09:10:03 danielk1977 Exp $
*/

#ifndef _PCACHE_H_

typedef struct PgHdr PgHdr;
typedef struct PCache PCache;

** of the suggested cache-sizes.
*/
int sqlite3PcacheGetCachesize(PCache *);
void sqlite3PcacheSetCachesize(PCache *, int);

/* Try to return memory used by the pcache module to the main memory heap */
int sqlite3PcacheReleaseMemory(int);

void sqlite3PcacheStats(int*,int*,int*,int*);

#endif /* _PCACHE_H_ */

**    May you share freely, never taking more than you give.
**
*************************************************************************
** Code for testing all sorts of SQLite interfaces.  This code
** is not included in the SQLite library.  It is used for automated
** testing of the SQLite library.
**
** $Id: test1.c,v 1.321 2008/08/29 09:10:03 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "tcl.h"
#include <stdlib.h>
#include <string.h>

/*

  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
  sqlite3_test_control(SQLITE_TESTCTRL_PRNG_RESET);
  return TCL_OK;
}

/*
** tclcmd:  pcache_stats
*/
static int test_pcache_stats(
  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
  int objc,              /* Number of arguments */
  Tcl_Obj *CONST objv[]  /* Command arguments */
){
  int nMin;
  int nMax;
  int nCurrent;
  int nRecyclable;
  Tcl_Obj *pRet;

  sqlite3PcacheStats(&nCurrent, &nMax, &nMin, &nRecyclable);

  pRet = Tcl_NewObj();
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("current", -1));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCurrent));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("max", -1));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMax));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("min", -1));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nMin));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewStringObj("recyclable", -1));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nRecyclable));

  Tcl_SetObjResult(interp, pRet);

  return TCL_OK;
}


/*
** Register commands with the TCL interpreter.
*/
int Sqlitetest1_Init(Tcl_Interp *interp){
  extern int sqlite3_search_count;
  extern int sqlite3_interrupt_count;

#ifdef SQLITE_ENABLE_COLUMN_METADATA
     { "sqlite3_table_column_metadata", test_table_column_metadata, 0  },
#endif
#ifndef SQLITE_OMIT_INCRBLOB
     { "sqlite3_blob_read",  test_blob_read, 0  },
     { "sqlite3_blob_write", test_blob_write, 0  },
#endif
     { "pcache_stats",       test_pcache_stats, 0  },
  };
  static int bitmask_size = sizeof(Bitmask)*8;
  int i;
  extern int sqlite3_sync_count, sqlite3_fullsync_count;
  extern int sqlite3_opentemp_count;
  extern int sqlite3_like_count;
  extern int sqlite3_xferopt_count;

# 2008 August 29
#
# 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: pcache.test,v 1.1 2008/08/29 09:10:03 danielk1977 Exp $

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


# The pcache module limits the number of pages available to purgeable
# caches to the sum of the 'cache_size' values for the set of open
# caches. This block of tests, pcache-1.*, test that the library behaves
# corrctly when it is forced to exceed this limit.
#
do_test pcache-1.1 {
  db close
  pcache_stats
} {current 0 max 0 min 0 recyclable 0}

do_test pcache-1.2 {
  sqlite3 db test.db
  execsql "PRAGMA cache_size=10"
  pcache_stats
} {current 1 max 10 min 10 recyclable 1}

do_test pcache-1.3 {
  execsql {
    BEGIN;
    CREATE TABLE t1(a, b, c);
    CREATE TABLE t2(a, b, c);
    CREATE TABLE t3(a, b, c);
    CREATE TABLE t4(a, b, c);
    CREATE TABLE t5(a, b, c);
  }
  pcache_stats
} {current 6 max 10 min 10 recyclable 0}

do_test pcache-1.4 {
  execsql {
    CREATE TABLE t6(a, b, c);
    CREATE TABLE t7(a, b, c);
    CREATE TABLE t8(a, b, c);
    CREATE TABLE t9(a, b, c);
  }
  pcache_stats
} {current 10 max 10 min 10 recyclable 0}

do_test pcache-1.5 {
  sqlite3 db2 test.db
  execsql "PRAGMA cache_size=10" db2
  pcache_stats
} {current 11 max 20 min 20 recyclable 1}

do_test pcache-1.6 {
  execsql {
    BEGIN;
    SELECT * FROM sqlite_master;
  } db2
  pcache_stats
} {current 11 max 20 min 20 recyclable 0}

# At this point connection db2 has a read lock on the database file and a 
# single pinned page in its cache. Connection [db] is holding 10 dirty 
# pages. It cannot recycle them because of the read lock held by db2.
#
do_test pcache-1.6 {
  execsql {
    CREATE INDEX i1 ON t1(a, b);
    CREATE INDEX i2 ON t2(a, b);
    CREATE INDEX i3 ON t3(a, b);
    CREATE INDEX i4 ON t4(a, b);
    CREATE INDEX i5 ON t5(a, b);
    CREATE INDEX i6 ON t6(a, b);
    CREATE INDEX i7 ON t7(a, b);
    CREATE INDEX i8 ON t8(a, b);
    CREATE INDEX i9 ON t9(a, b);
  } 
  pcache_stats
} {current 20 max 20 min 20 recyclable 0}

do_test pcache-1.7 {
  execsql {
    CREATE TABLE t10(a, b, c);
  } 
  pcache_stats
} {current 21 max 20 min 20 recyclable 0}

# Rolling back the transaction held by db2 at this point releases a pinned
# page. Because the number of allocated pages is greater than the 
# configured maximum, this page should be freed immediately instead of
# recycled.
#
do_test pcache-1.8 {
  execsql {ROLLBACK} db2
  pcache_stats
} {current 20 max 20 min 20 recyclable 0}

do_test pcache-1.9 {
  execsql COMMIT
  pcache_stats
} {current 20 max 20 min 20 recyclable 20}

do_test pcache-1.10 {
  db2 close
  pcache_stats
} {current 10 max 10 min 10 recyclable 10}

do_test pcache-1.11 {
  execsql { PRAGMA cache_size = 20 }
  pcache_stats
} {current 10 max 20 min 10 recyclable 10}

do_test pcache-1.12 {
  execsql { 
    SELECT * FROM t1 ORDER BY a; SELECT * FROM t1;
    SELECT * FROM t2 ORDER BY a; SELECT * FROM t2;
    SELECT * FROM t3 ORDER BY a; SELECT * FROM t3;
    SELECT * FROM t4 ORDER BY a; SELECT * FROM t4;
    SELECT * FROM t5 ORDER BY a; SELECT * FROM t5;
    SELECT * FROM t6 ORDER BY a; SELECT * FROM t6;
    SELECT * FROM t7 ORDER BY a; SELECT * FROM t7;
    SELECT * FROM t8 ORDER BY a; SELECT * FROM t8;
    SELECT * FROM t9 ORDER BY a; SELECT * FROM t9;
  }
  pcache_stats
} {current 19 max 20 min 10 recyclable 19}

do_test pcache-1.13 {
  execsql { PRAGMA cache_size = 15 }
  pcache_stats
} {current 15 max 15 min 10 recyclable 15}

finish_test