Postgres for MySQL DBAs

Transcription

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2 Postgres for MySQL DBAs JOHN CESARIO RYAN LOWE PGCONFSV2015

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4 TERMINOLOGY

5 Schema A schema is a named collection of tables. A schema can also contain views, indexes, sequences, data types, operators, and functions. Schemas are analogous to directories at the operating system level, except that schemas cannot be nested.

6 Database A database is a named collection of SQL objects. Generally, every database object belongs to one and only one database. More accurately, a database is a collection of schemas and the schemas contain the tables, functions, etc. So the full hierarchy is: server, database, schema, table.

7 PostgreSQL server->database->schema->table MySQL database->database->table [server instance]->schema->table

8 Storage Engines

9 Installation

10 Distributions PostgreSQL: Distro Packages Source MySQL: Distro Packages Source Binary Tarball

11 Overview Install repo Install package initdb pg_ctl initdb service postgresql-9.4 initdb start

12 First Login

13 > sudo -u postgres psql psql (9.4.5) Type "help" for help. postgres=#

14 test=# test=# create table dogs ( test(# name varchar(80), test(# owner varchar(80), test(# race varchar(80), test(# age int,

15 Post Install create database # CREATE DATABASE db1; CREATE DATABASE connect to the new database postgres=# \c db1 You are now connected to database "db1" as user "postgres". create schema # CREATE SCHEMA schema1; CREATE SCHEMA create role # CREATE ROLE user1 PASSWORD 'pass'; CREATE ROLE add permissions # GRANT ALL ON ALL TABLES IN SCHEMA schema1 TO user1; GRANT

16 Configuration Files MySQL /etc/my.cnf PostgreSQL $PGDATA/postgresql.conf $PGDATA/pg_hba.conf

17 postgresql.conf Main server option configuration file Located in datadir effective_cache_size shared_buffers work_mem

18 pg_hba.conf Located in datadir Used to control network access to the PostgreSQL server. Reload with: %> /usr/pgsql-9.4/bin/pg_ctl reload

19 Access Privilege

20 MySQL Access Privilege GRANT/REVOKE statements are the only first class citizen. All records are in the mysql schema. Pluggable Authentication (since 5.5). TCPIP, Socket (Unix), Named Pipe (Windows)

21 Postgres Access Privilege ROLES and GROUPS CREATE/ALTER ROLE, GRANT, REVOKE \du, pg_user, pg_shadow, etc etc pg_hba.conf <- This will bring you heartache

22 pg_hba.conf local database user auth-method [auth-options] host database user address auth-method [auth-options] hostssl database user address auth-method [auth-options] hostnossl database user address auth-method [auth-options] host database user IP-address IP-mask auth-method [auth-options] hostssl database user IP-address IP-mask auth-method [auth-options] hostnossl database user IP-address IP-mask auth-method [auth-options]

23 CLI MySQL PostgreSQL mysql XtraBackup mysql[d p]ump mysqlimport mysqladmin psql pg_basebackup pg_dump[all] pg_restore pg_ctl

24 Filesystem Layout

25 MySQL - datadir -- datadir/database -- database/{frm,ibd,myi,myd}

26 PG Data Directory PG_VERSION base global pg_clog pg_multixact pg_notify pg_serial pg_snapshots pg_stat pg_stat_tmp pg_subtrans pg_tblspc pg_twophase pg_xlog pg_log postmaster.opt postmaster.pid s A file containing the major version number of PostgreSQL Contains per-database subdirectories Contains cluster-wide tables, such as pg_database Contains trx commit status data Contains multitrx status data (used for shared row locks) Contains LISTEN/NOTIFY status data Contains information about committed serializable trx Contains exported snapshots Contains permanent files for the statistics subsystem Contains temporary files for the statistics subsystem Contains subtransaction status data Contains symbolic links to tablespaces Contains state files for prepared trx Contains WAL (Write Ahead Log) files Contains system logfiles. A file recording the command-line options the server was last started Postmaster withlock file

27 PostgreSQL - data directory -- base/oid -- tables, indexes, etc

28 Replication

29 MySQL Replication RBR, Mixed, Statement Galera, Tungsten Abstracted from transaction log (ib_logfile) Async by default, "semi-sync" available

30 Postgres Replication Streaming Repl Slony, pgpool, Bucardo Multiple interfaces for replication (trigger, statement, trx log)

31 Streaming Replication Async by default, "sync" available Use file-based continuous archiving Native Built into the transaction log

32 Replication: Configuration

33 Setting up Replication Add entry for replication user to pg_hba.conf Add Replication user Setup WAL Archiving Take base backup of master Place snapshot on standby Create recovery.conf on the standby server

34 Primary postgresql.conf wal_level max_wal_senders archive_command wal_keep_segments

35 pg_hba.conf hostssl replication repl /32 cert

36 recovery.conf standby_mode = on primary_conninfo = \ 'hostaddr= \ sslmode=require \ application_name=app1 \ user=repl \ password=xxx'

37 SHOW The SHOW command in PostgreSQL does not do what you think.

38 MySQL PostgreSQL SHOW DATABASES \list SHOW DATABASES \ds SHOW TABLES \dt DESCRIBE \d SHOW STATUS pg_stat_* views SHOW VARIABLES pg_settings use \c

39 SHOW... pg_* views and functions pg_stat_activity pg_stat_replication pg_settings

40 Making Configuration Changes

41 MySQL SET GLOBAL SESSION /etc/my.cnf Restart mysql for some options

42 Postgres SET [ SESSION LOCAL ] configuration_parameter { TO = } { value 'value' DEFAULT } pg_ctl reload pg_settings.context

43 Vacuum

44 MySQL Data is removed when deleted by the purge thread, which happens asynchronously.

45 Postgres Any data that is deleted will not be physically removed from the table until a VACUUM is run.

46 VACUUM Removes dead row versions and marks the space available for future reuse Only blocks DDL VACUUM FULL Removes dead row versions as well as reorganizes on disk structures Blocks all activity Returns space to the operating system Requires copy of table Autovacuum Runs VACUUM constantly in the background Enabled by default

47 PL/SQL PostgreSQL: RAISE MySQL: SIGNAL/RESIGNAL (5.5+)

48 MySQL vs PostgreSQL # vs -- ' " & ` vs ' & " lastname="lowe" vs lower(lastname)='lowe' 'foo' 'bar' vs 'foo' 'bar' \d vs \d

49 Q&A

50 square.com