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 1.17 2008/08/27 15:16:34 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** A complete page cache is an instance of this structure.
*/
struct PCache {

        return rc;
      }
      pcacheEnterGlobal();
    }
  }

  /* If the global page limit has been reached, try to recycle a page. */
  if( pcache.nCurrentPage>=pcache.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->szExtra!=szExtra) ){
    pcachePageFree(p);
    p = 0;

  p->szPage = szPage;
  p->szExtra = szExtra;
  p->bPurgeable = bPurgeable;
  p->xDestroy = xDestroy;
  p->xStress = xStress;
  p->pStress = pStress;
  p->nMax = 100;
  p->nMin = 20;

  pcacheEnterGlobal();
  if( bPurgeable ){
    pcache.nMaxPage += p->nMax;
    pcache.nMinPage += p->nMin;
  }

#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This file contains test cases focused on the two memory-management APIs, 
# sqlite3_soft_heap_limit() and sqlite3_release_memory().
#
# $Id: malloc5.test,v 1.19 2008/08/21 15:54:01 danielk1977 Exp $

#---------------------------------------------------------------------------
# NOTES ON EXPECTED BEHAVIOUR

#
#---------------------------------------------------------------------------


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

# Only run these tests if memory debugging is turned on.

}

sqlite3_soft_heap_limit 0
sqlite3 db test.db

do_test malloc5-1.1 {
  # Simplest possible test. Call sqlite3_release_memory when there is exactly
  # one unused page in a single pager cache. This test case set's the 
  # value of the ::pgalloc variable, which is used in subsequent tests.
  #
  # Note: Even though executing this statement on an empty database 
  # modifies 2 pages (the root of sqlite_master and the new root page), 
  # the sqlite_master root (page 1) is never freed because the btree layer
  # retains a reference to it for the entire transaction. 
  execsql {
    PRAGMA auto_vacuum=OFF;
    BEGIN;
    CREATE TABLE abc(a, b, c);
  }
  set ::pgalloc [sqlite3_release_memory]
  expr $::pgalloc > 0
} {1}

do_test malloc5-1.2 {
  # Test that the transaction started in the above test is still active.
  # Because the page freed had been written to, freeing it required a
  # journal sync and exclusive lock on the database file. Test the file
  # appears to be locked.


  sqlite3 db2 test.db
  catchsql {
    SELECT * FROM abc;
  } db2
} {1 {database is locked}}
do_test malloc5-1.3 {
  # Again call [sqlite3_release_memory] when there is exactly one unused page 
  # in the cache. The same amount of memory is required, but no journal-sync




  # or exclusive lock should be established.





  execsql {
    COMMIT;
    BEGIN;
    SELECT * FROM abc;
  }
  sqlite3_release_memory
} $::pgalloc

do_test malloc5-1.4 {
  # Database should not be locked this time.



  catchsql {
    SELECT * FROM abc;

  } db2
} {0 {}}
do_test malloc5-1.5 {
  # Manipulate the cache so that it contains two unused pages. One requires 
  # a journal-sync to free, the other does not.
  db2 close
  execsql {

    SELECT * FROM abc;
    CREATE TABLE def(d, e, f);
  }
  sqlite3_release_memory 500
} $::pgalloc

do_test malloc5-1.6 {
  # Database should not be locked this time. The above test case only
  # requested 500 bytes of memory, which can be obtained by freeing the page
  # that does not require an fsync().
  sqlite3 db2 test.db
  catchsql {
    SELECT * FROM abc;
  } db2
} {0 {}}
do_test malloc5-1.7 {
  # Release another 500 bytes of memory. This time we require a sync(), 
  # so the database file will be locked afterwards.

  db2 close
  sqlite3_release_memory 500
} $::pgalloc
do_test malloc5-1.8 {


  sqlite3 db2 test.db
  catchsql {
    SELECT * FROM abc;
  } db2
} {1 {database is locked}}
do_test malloc5-1.9 {
  execsql {
    COMMIT;
  }
} {}

do_test malloc5-2.1 {

  }
} {}
do_test malloc5-2.2 {
  # Load the root-page for table def into the cache. Then query table abc. 
  # Halfway through the query call sqlite3_release_memory(). The goal of this
  # test is to make sure we don't free pages that are in use (specifically, 
  # the root of table abc).

  set nRelease 0
  execsql { 
    BEGIN;
    SELECT * FROM def;
  }
  set data [list]
  db eval {SELECT * FROM abc} {

do_test malloc5-4.1 {
  execsql {BEGIN;}
  execsql {DELETE FROM abc;}
  for {set i 0} {$i < 10000} {incr i} {
    execsql "INSERT INTO abc VALUES($i, $i, '[string repeat X 100]');"
  }
  execsql {COMMIT;}



  set nMaxBytes [sqlite3_memory_highwater 1]
  puts -nonewline " (Highwater mark: $nMaxBytes) "
  expr $nMaxBytes > 1000000
} {1}
do_test malloc5-4.2 {
  sqlite3_release_memory
  sqlite3_soft_heap_limit 110000
  sqlite3_memory_highwater 1
  execsql {BEGIN;}
  for {set i 0} {$i < 10000} {incr i} {
    execsql "INSERT INTO abc VALUES($i, $i, '[string repeat X 100]');"
  }
  execsql {COMMIT;}
  set nMaxBytes [sqlite3_memory_highwater 1]
  puts -nonewline " (Highwater mark: $nMaxBytes) "

  # We used to test ($nMaxBytes<100000), because the soft-heap-limit is
  # 100000 bytes. But if an allocation that will exceed the 
  # soft-heap-limit is requested from within the only pager instance in 
  # the system, then there is no way to free memory and the limit has to 
  # be exceeded. An exception is memory allocated to store actual page
  # data (the code contains a special case for this).
  #
  # This is not a problem because all allocations apart from those
  # used to store cached page data are both small and transient.
  #
  # Summary: the actual high-water mark for memory usage may be slightly 
  # higher than the soft-heap-limit. The specific allocations that cause
  # the problem are the calls to sqlite3_malloc() inserted into selected
  # sqlite3OsXXX() functions in test builds.
  #
  expr $nMaxBytes <= 110100
} {1}
do_test malloc5-4.3 {
  # Check that the content of table abc is at least roughly as expected.
  execsql {
    SELECT count(*), sum(a), sum(b) FROM abc;
  }
} [list 20000 [expr int(20000.0 * 4999.5)] [expr int(20000.0 * 4999.5)]]

# Restore the soft heap limit.
sqlite3_soft_heap_limit $::soft_limit

# Test that there are no problems calling sqlite3_release_memory when
# there are open in-memory databases.
#

    [expr ([file size test.db]/1024)>20] [expr ([file size test2.db]/1024)>20]
} {1 1}
do_test malloc5-6.1.2 {
  list [execsql {PRAGMA cache_size}] [execsql {PRAGMA cache_size} db2]
} {10 10}

do_test malloc5-6.2.1 {

  execsql { SELECT * FROM abc } db2
  execsql {SELECT * FROM abc} db
  expr [nPage db] + [nPage db2]
} {20}

do_test malloc5-6.2.2 {
  # If we now try to reclaim some memory, it should come from the db2 cache.
  sqlite3_release_memory 3000

  # the rest of the db cache. But the db2 cache remains intact, because
  # SQLite tries to avoid calling sync().
  sqlite3_release_memory 9900
  list [nPage db] [nPage db2]
} {0 3}
do_test malloc5-6.3.5 {
  # But if we are really insistent, SQLite will consent to call sync()
  # if there is no other option.

  sqlite3_release_memory 1000
  list [nPage db] [nPage db2]
} {0 2}
do_test malloc5-6.3.6 {
  # The referenced page (page 1 of the db2 cache) will not be freed no
  # matter how much memory we ask for:
  sqlite3_release_memory 31459
  list [nPage db] [nPage db2]
} {0 1}

db2 close

sqlite3_soft_heap_limit $::soft_limit
finish_test
catch {db close}