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 1.573 2009/03/26 17:13:06 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
** the file-system for the given pager. A hot journal is one that 
** needs to be played back. According to this function, a hot-journal
** file exists if the following criteria are met:
**
**   * The journal file exists in the file system, and
**   * No process holds a RESERVED or greater lock on the database file, and
**   * The database file itself is greater than 0 bytes in size, and
**   * The first byte of the journal file exists and is not 0x00.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
** database with the same name. In this case the journal file is
** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
** is returned.
**
** This routine does not check if there is a master journal filename

** at the end of the file. If there is, and that master journal file


** does not exist, then the journal file is not really hot. In this
** case this routine will return a false-positive. The pager_playback()
** routine will discover that the journal file is not really hot and 
** will not roll it back. 
**
** If a hot-journal file is found to exist, *pExists is set to 1 and 
** SQLITE_OK returned. If no hot-journal file is present, *pExists is
** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
** to determine whether or not a hot-journal file exists, the IO error
** code is returned and the value of *pExists is undefined.
*/
static int hasHotJournal(Pager *pPager, int *pExists){
  sqlite3_vfs * const pVfs = pPager->pVfs;
  int rc;                       /* Return code */
  int exists;                   /* True if a journal file is present */


  assert( pPager!=0 );
  assert( pPager->useJournal );
  assert( isOpen(pPager->fd) );
  assert( !isOpen(pPager->jfd) );

  *pExists = 0;
  rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
  if( rc==SQLITE_OK && exists ){
    int locked;                 /* True if some process holds a RESERVED lock */
    rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
    if( rc==SQLITE_OK && !locked ){
      int nPage;

      /* Check the size of the database file. If it consists of 0 pages,
      ** then delete the journal file. See the header comment above for 
      ** the reasoning here.
      */
      rc = sqlite3PagerPagecount(pPager, &nPage);
      if( rc==SQLITE_OK ){
        if( nPage==0 ){
          rc = sqlite3OsDelete(pVfs, pPager->zJournal, 0);
        }else{
          /* The journal file exists and no other connection has a reserved
          ** or greater lock on the database file. Now check that there is
          ** at least one non-zero bytes at the start of the journal file.
          ** If there is, then we consider this journal to be hot. If not, 
          ** it can be ignored.
          */
          int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
          if( rc==SQLITE_OK ){
            u8 first = 0;
            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
            if( rc==SQLITE_IOERR_SHORT_READ ){
              rc = SQLITE_OK;
            }
            sqlite3OsClose(pPager->jfd);
            *pExists = (first!=0);
          }
        }
      }
    }
  }

  return rc;
}

/*
** Read the content for page pPg out of the database file and into 
** pPg->pData. A shared lock or greater must be held on the database
** file before this function is called.

  /* Open the journal file if it is not already open. */
  if( !isOpen(pPager->jfd) ){
    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
      sqlite3MemJournalOpen(pPager->jfd);
    }else{
      const int flags =                   /* VFS flags to open journal file */
        SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
        (pPager->tempFile ? 
          (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
          (SQLITE_OPEN_MAIN_JOURNAL)
        );
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
      rc = sqlite3JournalOpen(
          pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)

# 2009 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.
#
#***********************************************************************
#
# $Id: jrnlmode2.test,v 1.5 2009/03/26 17:13:06 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
}

#-------------------------------------------------------------------------
# Test overview:
#
#   jrnlmode2-1.*: Demonstrate bug #3745
#   jrnlmode2-2.*: Demonstrate bug #3751
#

do_test jrnlmode2-1.1 {
  execsql {
    PRAGMA journal_mode = persist;
    CREATE TABLE t1(a, b);
    INSERT INTO t1 VALUES(1, 2);
  }
} {persist}

do_test jrnlmode2-1.2 {
  file exists test.db-journal
} {1}

do_test jrnlmode2-1.3 {
  sqlite3 db2 test.db
  execsql { SELECT * FROM t1 } db2
} {1 2}

do_test jrnlmode2-1.4 {
  execsql {
    INSERT INTO t1 VALUES(3, 4);
    BEGIN;
    SELECT * FROM t1;
  }
  execsql { PRAGMA lock_status }
} {main shared temp closed}

do_test jrnlmode2-1.5 {
  file exists test.db-journal
} {1}

do_test jrnlmode2-1.6 {
  catchsql { SELECT * FROM t1 } db2
} {0 {1 2 3 4}}

do_test jrnlmode2-1.7 {
  execsql { COMMIT }
  catchsql { SELECT * FROM t1 } db2
} {0 {1 2 3 4}}



do_test jrnlmode2-2.1 {
  db2 close
  execsql { PRAGMA journal_mode = truncate }
  execsql { INSERT INTO t1 VALUES(5, 6) }
} {}

do_test jrnlmode2-2.2 {
  file exists test.db-journal
} {1}

do_test jrnlmode2-2.3 {
  file size test.db-journal
} {0}

do_test jrnlmode2-2.4 {
  sqlite3 db2 test.db -readonly 1
  catchsql { SELECT * FROM t1 } db2
} {0 {1 2 3 4 5 6}}

do_test jrnlmode2-2.5 {
  file delete test.db-journal
} {}

do_test jrnlmode2-2.6 {
  sqlite3 db2 test.db -readonly 1
  catchsql { SELECT * FROM t1 } db2
} {0 {1 2 3 4 5 6}}

catch { db2 close }
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 some common TCL routines used for regression
# testing the SQLite library
#
# $Id: tester.tcl,v 1.141 2009/03/26 17:13:06 danielk1977 Exp $

#
# What for user input before continuing.  This gives an opportunity
# to connect profiling tools to the process.
#
for {set i 0} {$i<[llength $argv]} {incr i} {
  if {[regexp {^-+pause$} [lindex $argv $i] all value]} {

  }
  sqlite3_soft_heap_limit 0
  incr nTest
  puts "$nErr errors out of $nTest tests"
  if {$nErr>0} {
    puts "Failures on these tests: $::failList"
  }
  run_thread_tests 1
  if {[llength $omitList]>0} {
    puts "Omitted test cases:"
    set prec {}
    foreach {rec} [lsort $omitList] {
      if {$rec==$prec} continue
      set prec $rec
      puts [format {  %-12s %s} [lindex $rec 0] [lindex $rec 1]]

    close $f
  }
}

# If the library is compiled with the SQLITE_DEFAULT_AUTOVACUUM macro set
# to non-zero, then set the global variable $AUTOVACUUM to 1.
set AUTOVACUUM $sqlite_options(default_autovacuum)

source $testdir/thread_common.tcl