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 1.339 2007/05/09 15:56:40 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

    }

    /* Populate the page with data, either by reading from the database
    ** file, or by setting the entire page to zero.
    */
    if( nMax<(int)pgno || MEMDB || (noContent && !pPager->alwaysRollback) ){
      if( pgno>pPager->mxPgno ){
        sqlite3PagerUnref(pPg);
        return SQLITE_FULL;
      }
      memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
      pPg->needRead = noContent && !pPager->alwaysRollback;
      IOTRACE(("ZERO %p %d\n", pPager, pgno));
    }else{
      rc = readDbPage(pPager, pPg, pgno);

#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This file contains tests to verify that the limits defined in
# sqlite source file limits.h are enforced.
#
# $Id: sqllimits1.test,v 1.6 2007/05/09 15:56:40 danielk1977 Exp $

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

# Test organization:
#
#     sqllimits-1.*:  SQLITE_MAX_LENGTH

do_test sqllimits1-3.6 {
  catchsql {
    SELECT COUNT(*) FROM trig;
  }
} {0 7}


#--------------------------------------------------------------------
# Test cases sqllimits1-4.* test the SQLITE_MAX_COLUMN limit.
#
do_test sqllimits-1.4.1 {
  # Columns in a table.
  set cols [list]
  for {set i 0} {$i <= $SQLITE_MAX_COLUMN} {incr i} {

#--------------------------------------------------------------------
# These tests - sqllimits-5.* - test that the SQLITE_MAX_EXPR_LENGTH
# limit is enforced. The limit refers to the number of terms in 
# the expression.
#
# TODO
do_test sqllimits-1.5.1 {
  execsql {
    PRAGMA max_page_count = 1000000;  -- 1 GB
    CREATE TABLE v0(a);
  }
  db transaction {
    for {set i 1} {$i < 2000} {incr i} {
      set expr "([string repeat {a AND } 50]a AND a) AS a"
      execsql [subst {
        CREATE VIEW v${i} AS SELECT $expr FROM v0
      }]
    }
  }
} {}

#--------------------------------------------------------------------
# Test cases sqllimits-6.* test that the SQLITE_MAX_VDBE_OP
# limit works as expected. The limit refers to the number of opcodes
# in a single VDBE program.
#
# TODO