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Indexing, Secondary Index, Indexing, Primary Index, Tight Binding VS Bind…

- - - - Lots of locality, too much seeking because records are not contiguous in the file.
      - Solution keep the file in memory.
    - - Rearrangement on secondary key is done after adding/updating entry. This is quicker because the SI file is small.
      - Deleting all records by placing "-1" in the reference field
        
        Index file is only affected.
- - - - If both key sizes are the same
        
        Update datafile
        
        Update PK Index and sort it without changing offset.
        
        Update SK index
    - - Same Key Sizes
        
        Update datafile.
        
        Update and sort secondary key index only.
      - Otherwise.
        
        Delete the old record and insert the new record
        
        To avoid changing the offset of all other records.
        
        Update the offset of the newly inserted record in PK index
        
        Update and sort secondary key index only.
    - - Same Record Sizes
        
        Update the datafile only.
      - Otherwise
        
        Update the secondary key index
        
        Update the offset of the newly inserted record in PK index (No need to reorder the primary index file.)
        
        Don't update the secondary index
- - - - Update both datafile and index file
      - No change in offset.
    - - Update the datafile.
      - If both new record and old record size are equal, don't update offset in index
      - Otherwise, Update offset of the record in the index. NOTE no need to sort the index again.