What’s New In PostgreSQL 9.3

What’s New In PostgreSQL 9.3 ?

Pavan DeolaseeNov 16, 2013

India PostgreSQL UserGroup MeetUp

Who am I ?

Pavan Deolasee

– http://www.linkedin.com/in/pavandeolasee Contributor to PostgreSQL and Postgres-XC Global

DevelopmentBest known for development of Heap-Only-Tuple (HOT) feature of PostgreSQL 8.3 release

– Contributed several other enhancements to PostgreSQL and derivatives

– Contributed to Postgres-XC's architectural design and implementation of several features

Currently works at NTT Data as a consultant

Previously worked for EnterpriseDB and Symantec/Veritas

Credits

● Magnus Hagander

● Michael Paquier

● Bruce Momjian

● Of course, all the developers

PostgreSQL Recap

PostgreSQL

– is world's most advanced open source database– is very stable– is fully compliant with ANSI SQL– supports foreign key, check constraints– supports various kinds of indexes– supports inheritance – is fully extensible (data types, procedural languages etc)– will recover your database in case of server failure

PostgreSQL Recap

PostgreSQL

– uses write-ahead-logs for durability and recover your database in case of server failure

– built-in log based streaming synchronous/asynchronous replication

– file system level backups and archive recovery

– point-in-time recovery

– hot standby

– upgrade in place

– full-text search

What’s New Really in 9.3 ?

● SQL features

● Performance features

● DBA features

● Many more general features

Auto Updatable Views

● Simple views are now updatable i.e. you can run INSERT/UPDATE/DELETE queries against a view that uses a single base relation

● Many restrictions apply

● More complex views can be updated via RULEs mechanism

Materialized Views

● Query is executed once and result is materialized on a stable storage

● Views must be refreshed manually

CREATE MATERIALIZED VIEW

..

AS query [ WITH [ NO ] DATA ]

LATERAL Support

● Subqueries appearing in FROM can be preceded by the key word LATERAL.

● This allows them to reference columns provided by preceding FROM items.

– Without LATERAL, each subquery is evaluated independently and so cannot cross-reference any other FROM item.

● LATERAL is primarily useful when the cross-referenced column is necessary for computing the row(s) to be joined.

– A common application is providing an argument value for a set-returning function

LATERAL Example

SELECT m.name FROM

manufacturers m LEFT JOIN

LATERAL get_product_names(m.id) pname

ON true WHERE pname IS NULL;

Range Type Enhancements

● SP-Gist index support for range types

● Statistics collection for range types thus improving query planning and execution

JSON Enhancements

● Operators and functions to extract elements from JSON values

● Allow JSON values to be converted into records

● Functions to convert scalars, records and hstore values to JSON

● Aggregates

Foreign Data Wrappers

● Several new features

● PostgreSQL FDW (postgres_fdw) is available in core now (forget the old dblink)

● Writable FDWs are now reality

● Many FDWs are already available

– Hbase

– MongoDB

– MySQL

– Oracle

COPY FREEZE

● Load tuples in frozen state to avoid another rewrite of the table

● A few restrictions apply

– A table must be truncated or created in the same transaction loading the frozen data

● A very useful tip to avoid significant IO overhead while working with large tables

Background Workers

● Step towards parallel query execution which is still a release or two away

● Background workers can be used with 9.3 if you have enough guts to write some cool C code

● Look at contrib/worker_spi for some sample code

Posix/mmap Shared Memory

● A step away from SysV Shared memory

● Most unix-like systems support Posix or mmap and PostgreSQL will use them by default

– A small SysV shared memory segment is still allocated for book keeping purposes

● No need to tune your kernel parameters or hit runtime issues because of hitting kernel limits

Page Level Checksums

● A great feature for checking data consistency

● Can be turned on (default is of) at the initdb time and must stay that way

– Comes at a cost● Errors can’t be corrected, but corruptions can be detected

very early in the cycle

Foreign Key Locking

● Improved concurrency since non-key updates don’t block foreign key checks

● New lock levels

– FOR KEY SHARE– FOR NO KEY UPDATE

● Foreign key triggers now take FOR KEY SHARE locks

● DMLs updating non key columns should take FOR NO KEY UPDATE locks thus avoiding blocking

Event Triggers

● They are more like DDL triggers

– Triggers are invoked when new database objects are created, updated or dropped

● Will be useful for logging, monitoring and even some replication solutions

● Three types of triggers - ddl_command_start, ddl_command_end, sql_drop

● More support expected in later releases

Parallel pg_dump

● Faster pg_dump by using multiple processes

– Better utilization of multiple cores

– Multiple tables are dumped in parallel

● Remember pg_restore can already run parallel jobs

Streaming-only Remastering

● "Remastering" is the process whereby a replica in a set of replicas becomes the new master for all of the other replicas.

– Master M1 is replicating to replicas R1, R2 and R3.

– Master M1 needs to be taken down for a hardware upgrade.

– The DBA promotes R1 to be the master.

– R2 and R3 are reconfigured & restarted, and now replicate from R1

Streaming-only Remastering

● In prior versions, it wasn’t possible to stream from new master without taking a fresh backup

● That restriction is now gone

Arch Independent Streaming

● Stream WAL from diferent OS and diferent architecture

– pg_basebackup and pg_receivexlog can now work cross platform

– You can’t apply WAL from diferent architecture, but this is still very useful for centralized backup etc

Many More

● pg_basebackup conf setup (-R option)

● Logging enhancements

● Recursive views

● COPY PIPE

● Include_dir directive

● Array enhancements

Resources

● Release Notes– http://www.postgresql.org/docs/9.3/static/release-9-3.html

● Planet PostgreSQL– http://planet.postgresql.org/

● Documentation– http://www.postgresql.org/docs/9.3/static/index.html

● Source Code– http://git.postgresql.org/gitweb/

Thank you

Pavan Deolaseepavan.deolasee@gmail.com

http://www.linkedin.com/in/pavandeolasee