PostgreSQL study notes – Features

  1. Object Relational Database Management System (ORDBMS) objects (eg: tables) can be related in a Hierarchy: Parent -> Child
  2. Transactional RDBMS: SQL statements have implicit: BEGIN; COMMIT: statements. SQL statements may also have explicit BEGIN COMMIT statements
  3. developed at UC Berkeley like along with bsd-unix
  4. One process per connection: master process = “postmaster” auto-spawns per new connection
  5. Processed (pid’s) use one cpu-core per connection: o/s may spawn new connections on a different cpu-core. no cross-core queries
  6. Multiple helper processes, which appear as ‘postgres’ instances, always running eg: stats collector, background writer (protect agains sudden failure ), auto-vacuum (cleanup/ space reclaimer), wal sender (that’s write ahead log)
  7. max db size: unlimited – limited by available storage.(terabytes, perabytes, exabytes)
  8. max table size: 32tb – stored as multiple 1gb files – changable (could be prob for some o/s’s)
  9. max row size: 400gb
  10. max column size: 1gb (per row ie: per field)
  11. max indexes per table: unlimited
  12. max identifier length (db objects – tables, columns, triggers, functions@ 63 bytes. this is extensible via source code
  13. default listener tcp port 5432. so may install postgresql as non-privilaged user
  14. users are distinct from o/s users
  15. users are authenticated globally (per server), then assigned permissions per database.
  16. inheratance. tables lower in hierachy may inherit columns from heigher tables (ie parents) so long as no contraints eg foreign keys.
  17. case insensative commands – without double quotes (eg: select * from syslog;)
  18. case sensative commands – with double quotes – (eg: select * from “syslog”;)
  19. three primary config files, located in postgres-root A.pg_hba.conf (host based access) B.postgresql.conf general settings C. pg_ident.conf – user mappings
  20. integrated log rotation (config by age or size)

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