Postgres for MySQL (and other database) people
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Thank you for the detailed presentation on Postgres. I have learned a lot about its philosophy, features, community and development process. Do you have any recommendations on the best ways for newcomers to get involved and contribute to the project?
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Postgres for MySQL (and other database) people
- 1. Postgres (for non-Postgres people) Greg Sabino Mullane End Point Corpora=on [email protected]
- 2. SELECT SUM(info) FROM talk; • Postgres philosophy and history • Conversion advice • Postgres gotchas • Postgres limitaCons and features • OrganizaCon and community • Development and infrastructure
- 3. The Part of Whys • Why MySQL? • Why Postgres? • Why me? • Why you?
- 4. • Postgres? PostgreSQL? Postgre? PostgresSQL? • Philosphy • Mercifully quick history lesson
- 5. MigraCng Your App • Schema • Data • ApplicaCon • Support
- 6. MigraCon : Schema • Mysqldump? • --compatible=postgresql --no-data • Redesign • Conversion tools
- 7. MigraCon : SQL Spec • Who cares? • Postgres vs. the spec • MySQL vs. the spec • Oracle vs. the spec • DB2 vs. the spec • MSSQL vs. the spec
- 8. MigraCon : Schema • Tables • Engines and plugins • CustomizaCon
- 9. MigraCon : Schema : Data Types : Numbers • INTEGER (smallint, bigint, serial) • NUMERIC (double precision, money) • REAL
- 10. MigraCon : Schema : Data Types : Text • TEXT • VARCHAR(n) • CHAR(n)
- 11. MigraCon : Schema : Data Types : Dates • DATE • TIMESTAMPTZ • TIME • INTERVAL
- 12. MigraCon : Schema : Data Types : Boolean • BOOL • TRUE, ‘t’, ‘y’, ‘yes’, ‘on’, 1 • FALSE, ‘f’, ‘n’, ‘no’, ‘off’, 0
- 14. MigraCon : Schema : Data Types : Others • Geometric (line, path, box, circle, polygon) • Arrays • ENUM • CIDR, INET, MACADDR • UUID • XML
- 15. MigraCon : Schema : Sequence • Auto‐increment • SEQUENCE • SERIAL • INTEGER NOT NULL DEFAULT nextval(‘foo’)
- 16. MigraCon : Schema : DEFAULT • cdate TIMESTAMPTZ NOT NULL DEFAULT now() • (almost) anything at all • No magic
- 17. MigraCon : Schema : FOREIGN KEYS • Fully supported • ON DELETE CASCADE • ON DELETE RESTRICT • ON DELETE SET NULL • ON DELETE SET DEFAULT • DEFERRED INITIALLY DEFERRED
- 18. MigraCon : Schema : Indexes • CREATE INDEX foo ON mytab(mycol); • CREATE INDEX foo2 ON mytab(mycol) WHERE size = ‘grande’; • CREATE INDEX foo3 ON mytab(LOWER(blurb)); • CREATE INDEX foo4 ON mytab(LOWER(blurb)) WHERE size = ‘grande’;
- 19. MigraCon : Schema : Indexes • CREATE INDEX CONCURENTLY foo ON mytab(mycol); • No rebuilding of tables • Reverse scan, bitmap
- 20. MigraCon : Schema : Triggers • CREATE TRIGGER mytrig BEFORE INSERT OR DELETE OR UPDATE ON mytab FOR EACH ROW EXECUTE PROCEDURE somefunc(); • Aside: funcCons and languages
- 21. MigraCon : Schema : FuncCons • Very custom • Pl/PGSQL == Pl/SQL • Very powerful
- 22. MigraCon : Data • No autocommit, fsync off, no autovacuum • COPY vs. INSERT • Turn off indexes and triggers (FK) • ANALYZE
- 23. ANALYZE • Cost‐based planner • Autovacuum • IniCal load • Default_staCsCcs_target – 10 – 100 – 1000 – More?
- 24. VACUUM • MVCC – Oracle vs. Pg • Rollback segment • Concurrency and locking • Table bloat • VACUUM FULL, CLUSTER, REINDEX
- 25. MigraCon : ApplicaCon • aka SQL • Clients (PHP excepCon) • SQL modes – TradiConal – Postgresql • “Any client can change its own session sql_mode value at any Cme.”
- 27. MigraCon : SQL : SELECT • Query planner • JOINS • Subselects
- 29. MigraCon : SQL : Text match • CHAR / VARCHAR / TEXT case sensiCve • SELECT count(*) FROM mytab WHERE mycol = ‘Fred’; • …WHERE LOWER(mycol) = ‘fred’;
- 30. MigraCon : SQL : full text search • Tsearch2: contrib vs. core • Powerful, complex • TransacConal!
- 31. MigraCon : SQL : DELETE • One table only • No LIMIT, no ORDER BY • No QUICK, LOW PRIORITY, IGNORE • DELETE FROM ONLY mytab WHERE… • DELETE FROM mytab USING otab WHERE mycol = otab.id AND otab.size = 'foo'; • DELETE FROM mytab WHERE mycol IN (SELECT id FROM otab WHERE size = ‘foo’);
- 32. MigraCon : SQL : UPDATE • Only one table • No ORDER BY, LIMIT, etc. • UPDATE mytab SET mycol=123 FROM otab WHERE mycol = otab.id AND otab.size = ‘foo’;
- 33. MigraCon : SQL : INSERT • Only one table • No REPLACE or ON DUPLICATE KEY UPDATE • UPSERT via plpgsql or app logic • DEFAULT • INSERT INTO mytab DEFAULT VALUES
- 34. MigraCon : SQL : || • Ugh • CONCAT • Wrapper funcCons • NULL an empty string
- 35. MigraCon : SQL: GRANT • ..and REVOKE • Almost any object • Immediate effect
- 36. MigraCon : SQL : locking • Use sparingly • Share, exclusive • Advisory • ALTER TABLE, REINDEX, VACUUM FULL
- 37. MigraCon : SQL : Aliases • AS opConal but recommended • SELECT SUM(mycol) AS mysum • SELECT * FROM pg_class c, mytab t…
- 38. MigraCon : SQL : Advanced • WITH • Windowing • Recursive funcCons
- 39. MigraCon : Support • RouCne stuff: autovacuum • Monitoring (check_postgres) • Backups (MVCC based)
- 40. Postgres : Quirks : lowercase • Implicit case folding • CREATE TABLE abc (A int); • CREATE TABLE ABC (a int); • CREATE TABLE “abc” (“a” int); • CREATE TABLE “ABC” (“A” int); • SELECT * FROM “ABC” WHERE “A”=123;
- 41. Postgres : Quirks : CasCng • 8.3 removed some implicit casts • SELECT 1 = ‘1’::text; • ERROR: operator does not exist: integer=text • 1. Fix the app • 2. Add the casts back in
- 42. Postgres : Quirks : COUNT(*) • MyISAM vs INNODB • Use an index • Triggers • SELECT reltuples FROM pg_class WHERE relname = ‘foo’;
- 43. Postgres : Quirks : Schemas • Database versus schemas versus cluster • Changes are cheap • No name‐based schemas • The ‘public’ schema • contrib/dblink
- 46. Postgres : Quirks : Hints • No hints per se • Smart planner • SET enable_* EXPLAIN • Few other knobs – per cluster
- 48. Postgres : Drawbacks • ReplicaCon pg_upgrade pg_upgrade • In‐place upgrade (pg_migrator, Bucardo) • Tuned for a toaster • Name • Publicity and markeCng
- 49. Postgres : Strengths • Custom everything • TransacConal DDL • PostGIS • Query planner • Support • AuthenCcaCon: pg_hba.conf – PAM, ident, Kerberos, LDAP, …
- 50. Postgres : OrganizaCon • Who? • Transparent meritocracy • “core” • Commirers • Mailing list, IRC, wiki • Company roles • Spread the risk • Cannot be bought (assets or people)
- 51. Postgres : Community • Core vs. “core” • Pgfoundry, github, bucardo.org, … • PostGIS • Mailing list? Bug report? User? • InteracCon! • Wiki, advocacy, sysadmin, docs, packagers • Clients, tools, replicaCon systems • Volunteers (IRC)
- 52. Postgres : Infrastructure • See Dave’s talk later today • Servers, companies • Build farm • Wiki • Commisest
- 53. Postgres : Development • Show me the money! • Individual developers vs. companies • CVS vs. git git wins! :) git wins! • Commirers vs. patchers vs. reviewers
- 54. Postgres : Version • Roughly every year • 8.3 8.3.10 • Major version, minor version, revision • Naming a version
- 55. Postgres : Patches • Bug report, mailing list post, TODO list • Run up the flagpole (Tom Lane test) – Stable? – Useful? – Spec compliant? – Side effects? – Best approach to problem? • Diff format, formaung, docs • Added to patch queue, commisest • Patch reviewer • Commit (20 vs 300)
- 56. Postgres : Patches • About that flagpole… • High standards • Cming • dfS
- 57. Postgres : Licensing • BSD (or MIT) PostgreSQL license • Free as in speech • Free as in beer • Plays well with others (PostGIS)
- 58. SELECT questions FROM audience;