DataBases - PostgreSQL

Linux System Administration II

Marian Marinov

Linux System Administration II DataBases - PostgreSQL

Important links

http://www.postgresql.org

PostgreSQL 9.3 Documentation

PostgreSQL Wiki

pgFoundry projects

pg-as-nosql-pgday-fosdem-2013.pdf

Linux System Administration II DataBases - PostgreSQL

Installation

Source

RPM/DEB

Linux System Administration II DataBases - PostgreSQL

Directory structure

basic

/var/lib/pgsql/data/*

Debian based

/etc/postgresql-common/

/etc/postgresql/9.3/main/

/var/lib/postgresql/9.3/main/

RedHat based

old versions /var/lib/pgsql/data/*

newer versions /var/lib/pgsql/9.3/data/*

Linux System Administration II DataBases - PostgreSQL

Structure of PostgreSQL

server

prefork (shared memory)

client handling (client library)

query parser

query analyzer

query planner

plug-in modules

storage engine

maintenance processes

client

client library

parser

autocomplete

Linux System Administration II DataBases - PostgreSQL

On disk data structure

\

|

|- PG_VERSION

|- base per-database subdirectories

|- global cluster-wide tables, such as pg_database

|- pg_clog transaction commit status data

|- pg_multixact multitransaction status data

|- pg_stat_tmp temporary files for the statistics subsystem

|- pg_subtrans subtransaction status data

|- pg_tblspc symbolic links to tablespaces

|- pg_twophase state files for prepared transactions

|- pg_xlog WAL (Write Ahead Log) files

|...

Linux System Administration II DataBases - PostgreSQL

On disk data structure

base -\

|- 1

|- 11510

|- 11511

|- 16384

\- 24576

template1=# SELECT datname,datlastsysoid FROM pg_database;

datname | datlastsysoid

-------------+----------------

template1 | 11510

template0 | 11510

postgres | 11510

os | 11510

(5 rows)

Linux System Administration II DataBases - PostgreSQL

On disk data structure

base -\

|- 11510 -\

| |- 24765

os# SELECT relname,relfilenode,reltablespace FROM pg_class

WHERE relfilenode=24765;

Relname | relfilenode | reltablespace

------------+---------------+---------------

disk_io | 24765 | 0

(1 row)

Linux System Administration II DataBases - PostgreSQL

On disk data structure

Table and Indexes are stored in separate files

Tables bigger then 1GB are split into different files:

filenode.1, filenode.2, . . . , filenode.N

The 1GB limit can be changed during build using–with-segsize configure option.

Linux System Administration II DataBases - PostgreSQL

DataBase Design

DBNAME SCHME OBJECTS

database -\ (table/view/sequence/domain)

|- public

|- scheme1 -----\

| |- table1

| |- table2

| |- view1

| |- view2

| |- seq1

| \- seq2

\- scheme2

Linux System Administration II DataBases - PostgreSQL

Configuration

authentication (pg hba.conf)

server (postgresql.conf)

storage considerations

Linux System Administration II DataBases - PostgreSQL

Working with PgSQL (psql and phpPgAdmin)

start/stop/restart/reload the server

server resouce limits(ulimits)

kernel tunning for PgSQL

Linux System Administration II DataBases - PostgreSQL

Working with PgSQL (psql and phpPgAdmin)

storage types

standard types

XML/JSON

Network datatypes

PostGIS

ARRAYs

User defined types (UDT)

tablespaces

list databases

list users

grant/revoke privileges

creating/destroying users

creating/destroying databases

creating/destroying schemas

creating/destroying tables

Linux System Administration II DataBases - PostgreSQL

Working with PgSQL (psql and phpPgAdmin)

creating/destroying constrains

creating/destroying indexes

creating/destroying sequences

VACUUM/AUTOVACUUM

VACUUM vs. ANALYZE

built-in functions

writing user functions

adding a language to a database

supported languages (SQL, pl/pgSQL, PL/Python, PL/Perl,PL/TCL, pl/V8, PL/R, PL/LUA, C)

adding an extension to a database

Foreign data wrappers

Linux System Administration II DataBases - PostgreSQL

Backup and restores

pg dump

pg dumpall

LVM snapshots

Via replication

WAL

Linux System Administration II DataBases - PostgreSQL

Monitoring

EXPLAIN ( Planner Cost Constants )

ps axf. . .

monitoring server

monitoring tables & indexes

Linux System Administration II DataBases - PostgreSQL