Ascertaining the distribution of data pages

Below is an example of an IBEBlock which scans a database file and retrieves some useful information about the distribution of database pages. You can also find this block in the \Blocks\Samples\DB Pages Statistics directory.

 execute ibeblock (DBFileName varchar(1000) comment 'Path to database file')
 returns (
   PageType varchar(100) comment 'Page Type',
   PageCount integer comment 'Page Count',
   PagePercent numeric(15,2) comment 'Page %',
   PageMb numeric(15,2) comment 'Size, Mb')
 as
 begin
   TimeStart = ibec_GetTickCount();
   iPageIndex = 0;
   aPages = ibec_Array(0,0,0,0,0,0,0,0,0,0,0);
   aPageTypes = ibec_Array('Unused', 'Database Header', 'Page Inventory Page', 'Transaction Inventory Page', 'Pointer Page',
                           'Data Page', 'Index Root Page', 'Index Page', 'Blob Data Page', 'Generator Page', 'Write Ahead Log');

   aBitMasks = ibec_Array(1, 2, 4, 8, 16, 32, 64, 128);

   fs = ibec_fs_OpenFile(DBFileName, __fmOpenRead + __fmShareDenyNone);
   if (fs is null) then
     Exit;
   try
     ibec_fs_Seek(fs, 16, __soFromBeginning);

     iPageSize = ibec_fs_ReadWord(fs);
     iPageSizeSub20 = iPageSize - 20;

     ibec_fs_Seek(fs, iPageSize + 20, __soFromBeginning);
     sPIP = ibec_fs_ReadString(fs, iPageSizeSub20);
     NextPIPIndex = iPageSizeSub20 * 8 - 1;

     ibec_fs_Seek(fs, 0, __soFromBeginning);
     while (not ibec_fs_Eof(fs)) do
     begin
       if (ibec_mod(iPageIndex, 100) = 0) then
       begin
         TimeSpent = ibec_Div(ibec_GetTickCount() - TimeStart, 1000);
         iSpeed = ibec_IIF((iPageIndex = 0) or (TimeSpent = 0), 0, ((iPageSize / 1024) * iPageIndex) / 1024 / TimeSpent);
         ibec_Progress(iPageIndex || '  :  ' || TimeSpent || '  :  ' || iSpeed || ' Mb/s');
       end;
       iVal = ibec_fs_ReadByte(fs);

       iPIPBytePos = ibec_mod(ibec_div(iPageIndex, 8), iPageSizeSub20) + 1;
       iPIPBitMaskIdx = ibec_mod(iPageIndex, 8);
       if (iPIPBitMaskIdx = 0) then
         iPIPByte = ibec_Ord(ibec_Copy(sPIP, iPIPBytePos, 1));
       iPIPBitMask = aBitMasks[iPIPBitMaskIdx];
       IsUsed = (ibec_and(iPIPBitMask, iPIPByte) = 0);

       if (IsUsed) then
         aPages[iVal] = aPages[iVal] + 1;
       else
         aPages[0] = aPages[0] + 1;

       if (iPageIndex = NextPIPIndex) then
       begin
         ibec_fs_Seek(fs, 19, __soFromCurrent);
         sPIP = ibec_fs_ReadString(fs, iPageSizeSub20);
         NextPIPIndex = NextPIPIndex + iPageSizeSub20 * 8;
       end;

       iPageIndex = iPageIndex + 1;
       ibec_fs_Seek(fs, iPageIndex * iPageSize, __soFromBeginning);
     end;

     PageType = 'Total Pages';
     PageCount = iPageIndex;
     PagePercent = 100;
     PageMb = (PageCount * (iPageSize / 1024)) / 1024;
     suspend;

     foreach (aPages as PageCnt key Idx skip nulls) do
     begin
       PageType = aPageTypes[Idx];
       PageCount = PageCnt;
       PagePercent = (PageCnt/iPageIndex) * 100;
       PageMb = (PageCount * (iPageSize / 1024)) / 1024;
       suspend;
     end
   finally
     ibec_fs_CloseFile(fs);
   end
 end