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 1.153 2004/07/22 15:02:25 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

  assert( pPager->state!=PAGER_UNLOCK );
  if( pPager->state==PAGER_SHARED ){
    assert( pPager->aInJournal==0 );
    if( pPager->memDb ){
      pPager->state = PAGER_EXCLUSIVE;
      pPager->origDbSize = pPager->dbSize;
    }else{

      int busy = 1;
      do {
        rc = sqlite3OsLock(&pPager->fd, RESERVED_LOCK);
      }while( rc==SQLITE_BUSY && 
          pPager->pBusyHandler && 
          pPager->pBusyHandler->xFunc && 
          pPager->pBusyHandler->xFunc(pPager->pBusyHandler->pArg, busy++)
      );


      if( rc!=SQLITE_OK ){







        return rc;
      }
      pPager->state = PAGER_RESERVED;
      pPager->dirtyCache = 0;
      TRACE2("TRANSACTION %d\n", pPager->fd.h);
      if( pPager->useJournal && !pPager->tempFile ){
        rc = pager_open_journal(pPager);

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.313 2004/08/04 14:29:23 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

#include "config.h"
#include "sqlite3.h"
#include "hash.h"

/*
** This macro casts a pointer to an integer.  Useful for doing
** pointer arithmetic.
*/
#define Addr(X)  ((uptr)X)

/*
** The maximum number of bytes of data that can be put into a single
** row of a single table.  The upper bound on this limit is
** 9223372036854775808 bytes (or 2**63).  We have arbitrarily set the
** limit to just 1MB here because the overflow page chain is inefficient
** for really big records and we want to discourage people from thinking that 
** multi-megabyte records are OK.  If your needs are different, you can
** change this define and recompile to increase or decrease the record
** size.
*/
#define MAX_BYTES_PER_ROW  1048576

/*
** If memory allocation problems are found, recompile with
**
**      -DSQLITE_DEBUG=1
**
** to enable some sanity checking on malloc() and free().  To
** check for memory leaks, recompile with

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.406 2004/07/24 17:38:29 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

    nHdr += sqlite3VarintLen(serial_type);
  }

  /* Add the initial header varint and total the size */
  nHdr += sqlite3VarintLen(nHdr);
  nByte = nHdr+nData;

  if( nByte>MAX_BYTES_PER_ROW ){
    rc = SQLITE_TOOBIG;
    goto abort_due_to_error;
  }

  /* Allocate space for the new record. */
  if( nByte>sizeof(zTemp) ){
    zNewRecord = sqliteMallocRaw(nByte);
    if( !zNewRecord ){
      goto no_mem;
    }
  }else{

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is stressing the library by putting large amounts
# of data in a single row of a table.
#
# $Id: bigrow.test,v 1.4 2001/11/24 00:31:47 drh Exp $

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

# Make a big string that we can use for test data
#
do_test bigrow-1.0 {

      UPDATE t1 SET b=b||b;
      SELECT a,length(b),c FROM t1;
    }
  } "one $sz hi"
  incr i
}
do_test bigrow-5.3 {
  set r [catch {execsql {UPDATE t1 SET b=b||b}} msg]
  lappend r $msg
} {1 {too much data for one table row}}
do_test bigrow-5.4 {









  execsql {DROP TABLE t1}
} {}

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: lock.test,v 1.26 2004/06/19 00:16:31 drh Exp $


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

# Create an alternative connection to the database
#

# A thread can read when another has a RESERVED lock.
#
do_test lock-2.2 {
  catchsql {SELECT * FROM t2} db2
} {0 {9 8}}

# If the other thread (the one that does not hold the transaction with
# a RESERVED lock) tries to get a RESERVED lock, we get a busy callback.
#
do_test lock-2.3 {
  proc callback {count} {
    set ::callback_value $count
    break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {UPDATE t1 SET a=b, b=a} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {1 {database is locked} 1}
do_test lock-2.4 {
  proc callback {count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {UPDATE t1 SET a=b, b=a} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {1 {database is locked} {1 2 3 4 5}}
do_test lock-2.5 {
  proc callback {count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {SELECT * FROM t1} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {0 {2 1} {}}

# In this test, the 3rd invocation of the busy callback causes
# the first thread to release its transaction.  That allows the
# second thread to continue.
#
do_test lock-2.6 {
  proc callback {count} {
    lappend ::callback_value $count
    if {$count>2} {
      execsql {ROLLBACK}
    }
  }
  set ::callback_value {}
  db2 busy callback
  set r [catch {execsql {SELECT * FROM t2} db2} msg]
  lappend r $msg
  lappend r $::callback_value
} {0 {9 8} {}}
do_test lock-2.7 {
  proc callback {count} {
    lappend ::callback_value $count
    if {$count>2} {
      execsql {ROLLBACK}
    }
  }
  set ::callback_value {}
  db2 busy callback
  execsql {BEGIN TRANSACTION} db2
  set r [catch {execsql {UPDATE t1 SET a = 0 WHERE 0} db2} msg]
  execsql {ROLLBACK} db2
  lappend r $msg
  lappend r $::callback_value
} {0 {} {1 2 3}}

# Test the built-in busy timeout handler
#
do_test lock-2.8 {
  db2 timeout 400
  execsql BEGIN
  execsql {UPDATE t1 SET a = 0 WHERE 0}
  catchsql BEGIN db2
  catchsql {UPDATE t1 SET a = 0 WHERE 0} db2
} {1 {database is locked}}
do_test lock-2.9 {
  db2 timeout 0
  execsql COMMIT
} {}
integrity_check lock-2.10

  proc callback {count} {
    lappend ::callback_value $count
    if {$count>4} break
  }
  db2 busy callback
  set rc [catch {db2 eval {UPDATE t1 SET a=0}} msg]
  lappend rc $msg $::callback_value
} {1 {database is locked} {1 2 3 4 5}}
execsql {ROLLBACK}

# When one thread is writing, other threads cannot read.  Except if the
# writing thread is writing to its temporary tables, the other threads
# can still read.  -> Not so in 3.0.  One thread can read while another
# holds a RESERVED lock.
#