Pages
The logical unit, that of database stores and reads the data.
Different according to DBMS (ex. PostgreSQL has a 8KB page, MySQL does 16KB)
DB handle data one or more pages in a single IO.
IO (physical IO)
Operation unit a request to disk.
Considered performance, developers should minimize this since this is expensive (on disk).
Some OS(ex. PostgreSQL) use OS cache instead of disk.
Logical I/O
Operation request to shared_buffers, os cache etc..
Index
Physical method of storing data.
- This is for searching data fast
- Consists of B-Tree data structure.
- Stored as pages.
B-Tree search operation Time Complexity is Log(N)
Heap
Everything is stored in here (disk).
More IO in this section, more cost and slower the queries.