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Storage Models & DataS Compression

Database Workloads​

The file storage we talked about are ideal for write-heavy workloads (i.e. INSERT/UPDATE/DELETE), but how about read workload (i.e. SELECT). The relationnal model does not specify that DBMS store all attributes of a tuple in a single page, so this may not be the best layout for some workloads.

On-Line Transaction Processing (OLTP) (usually build first)

  • Features of OLTP: fast operations that only read/update a small amount of data each time.

On-Line Analytical Processing (OLAP)

  • Features of OLAP: Complex queries that read a lot of data to compute an aggregate result
  • collect data from OLTP and aggregate them

Hybrid Transactional and Analytical Processing (HTAP)

  • Features of HTAP: a mix of OLTP and OLAP workloads

Storage Models​

A DBMS's storage model specifies how it physically organizes tuples on disk and in memory.

N-ary Storage Model (NSM)​

Use this model, the DBMS will stores almost all attributes of a single tuple contiguously in a single page. This model also known as row storage model.

  • ideal for OLTP workloads because it is efficient for retrieving a single tuple
  • typically with page size multiple of 4KB
  • store tuples' fixed-length and variable-length attributes in a single slotted page
  • tuples are identified by their record id (page#, slot#)