SQLite

**   * If mmap is being used, then the mapping is extended to szReq
**     bytes in size.
**
** SQLITE_OK is returned if successful, or an error code if an error occurs.
*/
int sqlite3PagerSetFilesize(Pager *pPager, i64 szReq){
  int rc;
  i64 sz;                         /* Size of file on disk in bytes */

  assert( pPager->eState==PAGER_OPEN );
  assert( pPager->nMmapOut==0 );

  rc = sqlite3OsFileSize(pPager->fd, &sz);
  if( rc==SQLITE_OK ){
    if( sz>szReq ){
      sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &sz);
    }
  }


  if( rc==SQLITE_OK ){
    i64 szMap = (szReq > pPager->nMapLimit) ? pPager->nMapLimit : szReq;
    if( pPager->nMapValid!=pPager->nMap || szMap!=pPager->nMap ){


      pPager->dbFileSize = (szReq / pPager->pageSize);
      rc = pagerMap(pPager, 1);
    }
  }

  return rc;
}

/*
** The argument is the first in a linked list of dirty pages connected

  set bt [btree_from_db $db]
  db_enter $db
  array set stats [btree_pager_stats $bt]
  db_leave $db
  return $stats(read)
}

foreach {t mmap_size nRead c2init} {
  1.1 { PRAGMA mmap_size = -65536 }   4 {}
  1.2 { PRAGMA mmap_size = -50    } 156 {}
  1.3 { PRAGMA mmap_size = 0      } 344 {}
  1.4 { PRAGMA mmap_size = -65536 }   4 {PRAGMA mmap_size = -65536}
  1.5 { PRAGMA mmap_size = -50    } 156 {PRAGMA mmap_size = -65536}
  1.6 { PRAGMA mmap_size = 0      } 344 {PRAGMA mmap_size = -65536}
} {
  do_multiclient_test tn {
    sql1 $mmap_size
    sql2 $c2init

    code2 {
      set ::rcnt 0
      proc rblob {n} {
        set ::rcnt [expr (($::rcnt << 3) + $::rcnt + 456) & 0xFFFFFFFF]
        set str [format %.8x [expr $::rcnt ^ 0xbdf20da3]] 
        string range [string repeat $str [expr $n/4]] 1 $n

    # Check that the number of pages read by connection 1 indicates that the
    # "PRAGMA mmap_size" command worked.
    do_test $t.$tn.5 { nRead db } $nRead
  }
}

set ::rcnt 0
proc rblob {n} {
  set ::rcnt [expr (($::rcnt << 3) + $::rcnt + 456) & 0xFFFFFFFF]
  set str [format %.8x [expr $::rcnt ^ 0xbdf20da3]] 
  string range [string repeat $str [expr $n/4]] 1 $n
}

reset_db
db func rblob rblob

do_execsql_test 2.1 {
  PRAGMA auto_vacuum = 1;
  PRAGMA mmap_size = -65536;
  PRAGMA journal_mode = wal;
  CREATE TABLE t1(a, b, UNIQUE(a, b));
  INSERT INTO t1 VALUES(rblob(500), rblob(500));
  INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --    2
  INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --    4
  INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --    8
  INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --   16
  INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --   32
  PRAGMA wal_checkpoint;
} {wal 0 103 103}

do_execsql_test 2.2 {
  PRAGMA auto_vacuum;
  SELECT count(*) FROM t1;
} {1 32}

do_test 2.3 {
  sqlite3 db2 test.db
  db2 func rblob rblob
  db2 eval { 
    DELETE FROM t1 WHERE (rowid%4);
    PRAGMA wal_checkpoint;
  }
  db2 eval { 
    INSERT INTO t1 SELECT rblob(500), rblob(500) FROM t1; --    16
    SELECT count(*) FROM t1;
  }
} {16}

do_execsql_test 2.4 {
  PRAGMA wal_checkpoint;
} {0 24 24}

finish_test

  return $txt
}

# Create a database schema.
#
do_test speed1p-1.0 {
  execsql {



    PRAGMA page_size=1024;
    PRAGMA cache_size=500;
    PRAGMA locking_mode=EXCLUSIVE;
    CREATE TABLE t1(a INTEGER, b INTEGER, c TEXT);
    CREATE TABLE t2(a INTEGER, b INTEGER, c TEXT);
    CREATE INDEX i2a ON t2(a);
    CREATE INDEX i2b ON t2(b);