SQLite

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.295 2007/03/26 08:05:12 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

}

/*
** Execute a rollback if a transaction is active and unlock the 
** database file. This is a no-op if the pager has already entered
** the error-state.
*/
static void pagerUnlockAndRollback(Pager *p){
  if( p->errCode ) return;
  if( p->state>=PAGER_RESERVED ){
    sqlite3PagerRollback(p);
  }
  pager_unlock(p);
  assert( p->errCode || !p->journalOpen || (p->exclusiveMode&&!p->journalOff) );
  assert( p->errCode || !p->stmtOpen || p->exclusiveMode );
}


/*
** Unlock the database and clear the in-memory cache.  This routine
** sets the state of the pager back to what it was when it was first
** opened.  Any outstanding pages are invalidated and subsequent attempts

  PgHdr *pPg;
  int rc = SQLITE_OK;
  assert( !MEMDB );
  if( pPager->state<PAGER_RESERVED ){
    return SQLITE_OK;
  }
  sqlite3PagerStmtCommit(pPager);
  if( pPager->stmtOpen && !pPager->exclusiveMode ){
    if( pPager->exclusiveMode ){
    sqlite3OsClose(&pPager->stfd);
    pPager->stmtOpen = 0;
    }else{
      sqlite3OsTruncate(pPager->stfd, 0);
    }
  }
  if( pPager->journalOpen ){
    if( pPager->exclusiveMode ){
      sqlite3OsTruncate(pPager->jfd, 0);
      sqlite3OsSeek(pPager->jfd, 0);
      pPager->journalOff = 0;
      pPager->journalStarted = 0;
    }else{
      sqlite3OsClose(&pPager->jfd);
      pPager->journalOpen = 0;
      sqlite3OsDelete(pPager->zJournal);
    }
    sqliteFree( pPager->aInJournal );
    pPager->aInJournal = 0;

  }else{
    assert( pPager->aInJournal==0 );
    assert( pPager->dirtyCache==0 || pPager->useJournal==0 );
  }
  if( !pPager->exclusiveMode ){
    rc = sqlite3OsUnlock(pPager->fd, SHARED_LOCK);
    pPager->state = PAGER_SHARED;
  }else if( pPager->state==PAGER_SYNCED ){




    pPager->state = PAGER_EXCLUSIVE;

    }

  pPager->origDbSize = 0;
  pPager->setMaster = 0;
  pPager->needSync = 0;
  pPager->pFirstSynced = pPager->pFirst;
  pPager->dbSize = -1;
  return rc;
}

  char *zMaster = 0;       /* Name of master journal file if any */

  /* Figure out how many records are in the journal.  Abort early if
  ** the journal is empty.
  */
  assert( pPager->journalOpen );
  rc = sqlite3OsFileSize(pPager->jfd, &szJ);
  if( rc!=SQLITE_OK || szJ==0 ){
    goto end_playback;
  }

  /* Read the master journal name from the journal, if it is present.
  ** If a master journal file name is specified, but the file is not
  ** present on disk, then the journal is not hot and does not need to be
  ** played back.

  assert( pPager!=0 );
  *ppPage = 0;
  if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
    return pPager->errCode;
  }

  /* If this is the first page accessed, then get a SHARED lock
  ** on the database file. pagerSharedLock() is a no-op if 
  ** a database lock is already held.
  */
  rc = pagerSharedLock(pPager);
  if( rc!=SQLITE_OK ){
    return rc;
  }
  assert( pPager->state!=PAGER_UNLOCK );

DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
  PgHdr *pPg;

  assert( pPager!=0 );
  assert( pgno!=0 );

  if( pPager->state==PAGER_UNLOCK ){
    assert( !pPager->pAll || pPager->exclusiveMode );
    return 0;
  }
  if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
    return 0;
  }
  pPg = pager_lookup(pPager, pgno);
  if( pPg==0 ) return 0;
  page_ref(pPg);
  return pPg;
}

  
    /* When all pages reach the freelist, drop the read lock from
    ** the database file.
    */
    pPager->nRef--;
    assert( pPager->nRef>=0 );
    if( pPager->nRef==0 ){

      pagerUnlockAndRollback(pPager);
    }
  }
  return SQLITE_OK;
}

/*

      }
      pPager->dirtyCache = 0;
      TRACE2("TRANSACTION %d\n", PAGERID(pPager));
      if( pPager->useJournal && !pPager->tempFile ){
        rc = pager_open_journal(pPager);
      }
    }
  }else if( pPager->journalOpen && pPager->journalOff==0 ){
    /* This happens when the pager was in exclusive-access mode last
    ** time a (read or write) transaction was successfully concluded
    ** by this connection. Instead of deleting the journal file it was 
    ** kept open and truncated to 0 bytes.
    */
    assert( pPager->nRec==0 );
    assert( pPager->origDbSize==0 );
    sqlite3PagerPagecount(pPager);
    pPager->origDbSize = pPager->dbSize;
    pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
    if( !pPager->aInJournal ){
      rc = SQLITE_NOMEM;
    }else{
      rc = writeJournalHdr(pPager);
  }
  }
  assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
  return rc;
}

/*
** Make a page dirty.  Set its dirty flag and add it to the dirty
** page list.
*/

  TRACE2("ROLLBACK %d\n", PAGERID(pPager));
  if( MEMDB ){
    PgHdr *p;
    for(p=pPager->pAll; p; p=p->pNextAll){
      PgHistory *pHist;
      assert( !p->alwaysRollback );
      if( !p->dirty ){


        assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pOrig );
        assert( !((PgHistory *)PGHDR_TO_HIST(p, pPager))->pStmt );
        continue;
      }

      pHist = PGHDR_TO_HIST(p, pPager);
      if( pHist->pOrig ){

    if( pPager->state>=PAGER_EXCLUSIVE ){
      pager_playback(pPager, 0);
    }
    return pPager->errCode;
  }
  if( pPager->state==PAGER_RESERVED ){
    int rc2;

    rc = pager_playback(pPager, 0);
    rc2 = pager_unwritelock(pPager);
    if( rc==SQLITE_OK ){
      rc = rc2;
    }
  }else{
    rc = pager_playback(pPager, 0);

# 2007 March 24
#
# 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 regression tests for SQLite library.
#
# $Id: exclusive.test,v 1.2 2007/03/26 08:05:12 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return

do_test exclusive-3.4 {
  execsql {
    BEGIN;
    UPDATE abc SET a = 1, b = 2, c = 3;
    ROLLBACK;
    SELECT * FROM abc;
  }
} {A B C}
do_test exclusive-3.5 {
  filestate test.db-journal
} {1 0}
do_test exclusive-3.6 {
  execsql {
    PRAGMA locking_mode = normal;
    SELECT * FROM abc;
  }
  filestate test.db-journal
} {0 0}

#----------------------------------------------------------------------
# Tests exclusive-4.X - test that rollback works correctly when
# in exclusive-access mode.
#

# The following procedure computes a "signature" for table "t3".  If
# T3 changes in any way, the signature should change.  
#
# This is used to test ROLLBACK.  We gather a signature for t3, then
# make lots of changes to t3, then rollback and take another signature.
# The two signatures should be the same.
#
proc signature {} {
  return [db eval {SELECT count(*), md5sum(x) FROM t3}]
}



do_test exclusive-4.0 {



  execsql { PRAGMA locking_mode = exclusive; }
  execsql { PRAGMA default_cache_size = 10; }
  execsql {
    BEGIN;
    CREATE TABLE t3(x TEXT);
    INSERT INTO t3 VALUES(randstr(10,400));
    INSERT INTO t3 VALUES(randstr(10,400));
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;





    COMMIT;
  }
  execsql {SELECT count(*) FROM t3;}
} {32}


set ::X [signature]
do_test exclusive-4.1 {
  execsql {
    BEGIN;
    DELETE FROM t3 WHERE random()%10!=0;
    INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
    INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
    SELECT count(*) FROM t3;
    ROLLBACK;
  }
  signature
} $::X

do_test exclusive-4.2 {
  execsql {
    BEGIN;
    DELETE FROM t3 WHERE random()%10!=0;
    INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
    DELETE FROM t3 WHERE random()%10!=0;
    INSERT INTO t3 SELECT randstr(10,10)||x FROM t3;
    ROLLBACK;
}
  signature
} $::X

do_test exclusive-4.3 {
  execsql {
    INSERT INTO t3 SELECT randstr(10,400) FROM t3 WHERE random()%10==0;
  }
} {}

do_test exclusive-4.4 {
  catch {set ::X [signature]}
} {0}
do_test exclusive-4.5 {
  execsql {
    PRAGMA locking_mode = NORMAL;
    DROP TABLE t3;
    DROP TABLE abc;
  }
} {normal}

#----------------------------------------------------------------------
# Tests exclusive-5.X - test that statement journals are truncated
# instead of deleted when in exclusive access mode.
#
#set sqlite_os_trace 1
do_test exclusive-5.0 {
  execsql {
    CREATE TABLE abc(a UNIQUE, b UNIQUE, c UNIQUE);
    BEGIN;
    INSERT INTO abc VALUES(1, 2, 3);
    INSERT INTO abc SELECT a+1, b+1, c+1 FROM abc;
  }
} {}
do_test exclusive-5.1 {
  # Three files are open: The db, journal and statement-journal.
  set sqlite_open_file_count
} {3}
do_test exclusive-5.2 {
  execsql {
    COMMIT;
  }
  # One file open: the db.
  set sqlite_open_file_count
} {1}
do_test exclusive-5.3 {
  execsql {
    PRAGMA locking_mode = exclusive;
    BEGIN;
    INSERT INTO abc VALUES(5, 6, 7);
  }
  # Two files open: the db and journal.
  set sqlite_open_file_count
} {2}
do_test exclusive-5.4 {
  execsql {
    INSERT INTO abc SELECT a+10, b+10, c+10 FROM abc;
  }
  # Three files are open: The db, journal and statement-journal.
  set sqlite_open_file_count
} {3}
do_test exclusive-5.5 {
  execsql {
    COMMIT;
  }
  # Three files are still open: The db, journal and statement-journal.
  set sqlite_open_file_count
} {3}
do_test exclusive-5.6 {
  execsql {
    PRAGMA locking_mode = normal;
    SELECT * FROM abc;
  }
} {normal 1 2 3 2 3 4 5 6 7 11 12 13 12 13 14 15 16 17}
do_test exclusive-5.7 {
  # Just the db open.
  set sqlite_open_file_count
} {1}

finish_test

# 2001 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 implements regression tests for SQLite library.  The
# focus of this script is database locks.
#
# $Id: trans.test,v 1.34 2007/03/26 08:05:12 danielk1977 Exp $


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


# Create several tables to work with.

#
do_test trans-9.1 {
  execsql {
    PRAGMA default_cache_size=10;
  }
  db close
  sqlite3 db test.db

  execsql {
    BEGIN;
    CREATE TABLE t3(x TEXT);
    INSERT INTO t3 VALUES(randstr(10,400));
    INSERT INTO t3 VALUES(randstr(10,400));
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;
    INSERT INTO t3 SELECT randstr(10,400) FROM t3;