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 1.447 2008/05/15 08:34:54 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include <assert.h>
#include <string.h>

/*

** This routine clears the needSync field of every page current held in
** memory.
*/
static int syncJournal(Pager *pPager){
  PgHdr *pPg;
  int rc = SQLITE_OK;


  /* Sync the journal before modifying the main database
  ** (assuming there is a journal and it needs to be synced.)
  */
  if( pPager->needSync ){
    if( !pPager->tempFile ){
      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
      assert( pPager->journalOpen );

  pPg = pPager->lru.pFirstSynced;

  /* If we could not find a page that does not require an fsync()
  ** on the journal file then fsync the journal file.  This is a
  ** very slow operation, so we work hard to avoid it.  But sometimes
  ** it can't be helped.
  */
  if( pPg==0 && pPager->lru.pFirst ){
    if( !pPager->errCode ){
      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
      int rc = syncJournal(pPager);
      if( rc!=0 ){
        return rc;
      }
      if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
        /* If in full-sync mode, write a new journal header into the
        ** journal file. This is done to avoid ever modifying a journal
        ** header that is involved in the rollback of pages that have
        ** already been written to the database (in case the header is
        ** trashed when the nRec field is updated).
        */
        pPager->nRec = 0;
        assert( pPager->journalOff > 0 );
        assert( pPager->doNotSync==0 );
        rc = writeJournalHdr(pPager);
        if( rc!=0 ){
          return rc;
        }
      }
    }
    pPg = pPager->lru.pFirst;
  }

  assert( pPg->nRef==0 );

  /* Write the page to the database file if it is dirty.
  */
  if( pPg->dirty && !pPager->errCode ){
    int rc;
    assert( pPg->needSync==0 );
    makeClean(pPg);
    pPg->dirty = 1;
    pPg->pDirty = 0;
    rc = pager_write_pagelist( pPg );
    pPg->dirty = 0;
    if( rc!=SQLITE_OK ){
      return rc;
    }
  }
  assert( pPg->dirty==0 || pPager->errCode );

  /* If the page we are recycling is marked as alwaysRollback, then
  ** set the global alwaysRollback flag, thus disabling the
  ** sqlite3PagerDontRollback() optimization for the rest of this transaction.
  ** It is necessary to do this because the page marked alwaysRollback
  ** might be reloaded at a later time but at that point we won't remember
  ** that is was marked alwaysRollback.  This means that all pages must

# 2008 May 12
#
# 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 tests that if sqlite3_release_memory() is called to reclaim
# memory from a pager that is in the error-state, SQLite does not 
# incorrectly write dirty pages out to the database (not safe to do
# once the pager is in error state).
#
# $Id: ioerr5.test,v 1.1 2008/05/15 08:34:54 danielk1977 Exp $

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

ifcapable !memorymanage||!shared_cache {
  finish_test
  return
}

db close

set ::enable_shared_cache [sqlite3_enable_shared_cache 1]
set ::soft_limit [sqlite3_soft_heap_limit 1048576]

# This procedure prepares, steps and finalizes an SQL statement via the
# UTF-16 APIs. The text representation of an SQLite error code is returned
# ("SQLITE_OK", "SQLITE_IOERR" etc.). The actual results returned by the
# SQL statement, if it is a SELECT, are not available.
#
# This can be useful for testing because it forces SQLite to make an extra 
# call to sqlite3_malloc() when translating from the supplied UTF-16 to
# the UTF-8 encoding used internally.
#
proc dosql16 {zSql {db db}} {
  set sql [encoding convertto unicode $zSql]
  append sql "\00\00"
  set stmt [sqlite3_prepare16 $db $sql -1 {}]
  sqlite3_step $stmt
  set rc [sqlite3_finalize $stmt]
}

proc compilesql16 {zSql {db db}} {
  set sql [encoding convertto unicode $zSql]
  append sql "\00\00"
  set stmt [sqlite3_prepare16 $db $sql -1 {}]
  set rc [sqlite3_finalize $stmt]
}

# Open two database connections (handle db and db2) to database "test.db".
#
proc opendatabases {} {
  catch {db close}
  catch {db2 close}
  sqlite3 db test.db
  sqlite3 db2 test.db
  db2 cache size 0
  db cache size 0
  execsql {
    pragma page_size=512;
    pragma auto_vacuum=2;
    pragma cache_size=16;
  }
}

# Open two database connections and create a single table in the db.
#
do_test ioerr5-1.0 {
  opendatabases
  execsql { CREATE TABLE A(Id INTEGER, Name TEXT) }
} {}

foreach locking_mode {normal exclusive} {
  for {set iFail 1} {$iFail<200} {incr iFail} {
    sqlite3_soft_heap_limit 1048576
    opendatabases
    execsql { pragma locking_mode=exclusive }
    set nRow [db one {SELECT count(*) FROM a}]
  
    # Dirty (at least) one of the pages in the cache.
    do_test ioerr5-$locking_mode-$iFail.1 {
      execsql {
        BEGIN EXCLUSIVE;
        INSERT INTO a VALUES(1, 'ABCDEFGHIJKLMNOP');
      }
    } {}
  
    # Now try to commit the transaction. Cause an IO error to occur
    # within this operation, which moves the pager into the error state.
    #
    set ::sqlite_io_error_persist 1
    set ::sqlite_io_error_pending $iFail
    do_test ioerr5-$locking_mode-$iFail.2 {
      set rc [catchsql {COMMIT}]
      list
    } {}
    set ::sqlite_io_error_hit 0
    set ::sqlite_io_error_persist 0
    set ::sqlite_io_error_pending 0
  
    # Read the contents of the database file into a Tcl variable.
    #
    set fd [open test.db]
    fconfigure $fd -translation binary -encoding binary
    set zDatabase [read $fd]
    close $fd

    # Set a very low soft-limit and then try to compile an SQL statement 
    # from UTF-16 text. To do this, SQLite will need to reclaim memory
    # from the pager that is in error state. Including that associated
    # with the dirty page.
    #
    do_test ioerr5-$locking_mode-$iFail.3 {
      sqlite3_soft_heap_limit 1024
      compilesql16 "SELECT 10"
      set bt [btree_from_db db]
      array set stats [btree_pager_stats $bt]
      set stats(page)
    } {0}

    # Ensure that nothing was written to the database while reclaiming
    # memory from the pager in error state.
    #
    do_test ioerr5-$locking_mode-$iFail.4 {
      set fd [open test.db]
      fconfigure $fd -translation binary -encoding binary
      set zDatabase2 [read $fd]
      close $fd
      expr {$zDatabase eq $zDatabase2}
    } {1}
  
    if {$rc eq [list 0 {}]} {
      do_test ioerr5-$locking_mode-$iFail.3 {
        execsql { SELECT count(*) FROM a }
      } [expr $nRow+1]
      break
    }
  }
}

sqlite3_enable_shared_cache $::enable_shared_cache
sqlite3_soft_heap_limit $::soft_limit

finish_test