PostgreSQL 9.6 새 기능 소개

PostgreSQL 9.6 새 기능
이지호(search5@gmail.com)

강연자 소개
u 이름: 이지호, 호: 서치(슬기 서, 기다릴 치), 영문 중간 이름: persy
u 소속: 한국방송통신대학교 대학원 정보과학과, (주)위비즈넷, 사단법인 E.S.C
u 98년 알짜레드햇 6.0에서 PostgreSQL 6.4를 보고 아!!! 이거다!!

PostgreSQL은 어떤 데이터베이스에요?
u PostgreSQL은 1986년 캘리포니아 버클리에서 시작해 1988년 만들어진 BSD 기반의 오픈소
스 데이터베이스
u 이후 여러번의 지속적인 개선을 통해 1996년 PostgreSQL 발표.
u PostgreSQL이 제공하는 특징
u 연산자, 복합 자료형, 집계 함수, 자료형 변환자, 확장 함수 등 제공
u 테이블 생성 및 조회시 상속 기능 사용 가능
u 함수(프로시저) 사용 가능(pl/pgsql이 공식이나 python, java, php, perl, tcl도 가능)
u 이름은 어떻게 부르나요? -> 여러분이 부르고 싶은대로 부르세요.

PostgreSQL 커뮤니티
u 한국 PostgreSQL 사용자 모임은
u http://www.facebook.com/groups/postgres.kr
u 2016년 10월 10일 기준 1,030명에 이르는 회원수를 자랑합니다.
u 모임은?
u 매달 넷째주 일요일에 애 안봐도 되고, 애인 안 만나도 되고, 다른 할 일도 없는 분들이
모여 정기 기술 세미나를 오후 2시 ~ 오후 5시까지 하고,
u 주말의 필수품목인 ‘알콜’ Drinking을 하지 않는 정말 건전한 모임을 합니다.

Parallel execution of sequential scans,
joins and aggregates

u max_parallel_workers_per_gather (integer) - 병렬 쿼리를 실행할 작업자 수. 기본값 0
u max_worker_processes (integer) - 백그라운드 프로세스의 최대 수. 기본값: 시스템 코어 수
u parallel_setup_cost (floating point) - Sets the planner's estimate of the cost of launching
parallel worker processes. The default is 1000.
u parallel_tuple_cost (floating point) - Sets the planner's estimate of the cost of transferring
one tuple from a parallel worker process to another process. The default is 0.1.
u min_parallel_relation_size (integer) - Sets the minimum size of relations to be considered
for parallel scan. The default is 8 megabytes (8MB).

=# EXPLAIN SELECT count(*) FROM partest;
QUERY PLAN
-----------------------------------------------------------------------
Aggregate (cost=37059.38..37059.39 rows=1 width=8)
-> Seq Scan on partest (cost=0.00..31417.50 rows=2256750 width=0)

template1=# set max_parallel_workers_per_gather = 1;
template1=# EXPLAIN SELECT count(*) FROM partest;
QUERY PLAN
-----------------------------------------------------------------------
Finalize Aggregate (cost=24556.00..24556.01 rows=1 width=8)
-> Gather (cost=24555.88..24555.99 rows=1 width=8)
Workers Planned: 1
-> Partial Aggregate (cost=23555.88..23555.89 rows=1 width=8)
-> Parallel Seq Scan on partest (cost=0.00..20614.71 rows=1176471 width=0)

template1=# EXPLAIN SELECT count(*) FROM partest;
QUERY PLAN
-----------------------------------------------------------------------
Finalize Aggregate (cost=20266.88..20266.89 rows=1 width=8)
-> Gather (cost=20266.67..20266.88 rows=1 width=8)
Workers Planned: 2
-> Partial Aggregate (cost=19266.67..19266.68 rows=1 width=8)
-> Parallel Seq Scan on partest (cost=0.00..17183.33 rows=833333 width=0)

template1=# explain analyze select min(col1) from partest;
QUERY PLAN
-----------------------------------------------------------------------
Finalize Aggregate (cost=127493.90..127493.91 rows=1 width=8) …
-> Gather (cost=127493.37..127493.88 rows=5 width=8) …
Workers Planned: 5
Workers Launched: 5
-> Partial Aggregate (cost=126493.37..126493.38 rows=1 width=8) …
-> Parallel Seq Scan on partest (cost=0.00..121493.30 rows=…) …
Planning time: 0.110 ms
Execution time: 1422.139 ms

template1=# explain analyze select min(col1) from partest;
QUERY PLAN
-----------------------------------------------------------------------
Finalize Aggregate (cost=127493.90..127493.91 rows=1 width=8) …
-> Gather (cost=127493.37..127493.88 rows=5 width=8) …
Workers Planned: 6
Workers Launched: 6
-> Partial Aggregate (cost=126493.37..126493.38 rows=1 width=8) …
-> Parallel Seq Scan on partest (cost=0.00..121493.30 rows=…) …
Planning time: 0.110 ms
Execution time: 1422.139 ms

Autovacuum no longer performs
repetitive scanning of old data
u PostgreSQL 9.6 부터 성능 향상을 위해 영구보관용 데이터에 대해서
auto vacuum 중지
u PostgreSQL 9.6 이전까지 모든 힙 페이지 스캔
u 9.6은 마지막 동결 이후 수정된 페이지만 스캔
u 이 결정 덕분에 쓰기가 드문 테이블 성능 향상 혜택

Synchronous replication now allows multiple
standby servers for increased reliability
How replication works

synchronous_commit = off

synchronous_commit = local

synchronous_commit = on (default)

synchronous_commit = remote_write

synchronous_commit = remote_apply

u synchronous_standby_names =
‘standby_name [,
…]’
u synchronous_standby_names =
‘num (standby_name [,
…])’
u ex)
synchronous_standby_names =
‘2(*)’
u synchronous_standby_names is
empty
u If
this parameter
is
empty as
shown it
changes behaviour of

setting synchronous_commit to on, remote_write or remote_apply to
behave same

as local (ie,
the COMMIT will only wait for
flushing to
local disk).

postgres_fdw now supports remote
joins, sorts, UPDATEs, and DELETEs
FDW
Foreign
Server
Foreign
Server
Foreign
Server
SQL 쿼리
Join, Sort, Updates, Deletes

Allow Limiting of Snapshot Age
old_snapshot_threshold 값은 서버를 시작할때만 설정 가능(DEFAULT: -1, 0, 1min - 60d)
Session 1 Session 2
show old_snapshot_threshold;;
create table snaptest(x int);;
insert into snaptest values (1);;
begin work;;
set transaction isolation level serializable;;
select * from snaptest;;
update snaptest set x = 2;;
select pg_sleep(100);;
vacuum snaptest;;
select * from snaptest;;
ERROR:snapshot too old;;

Allow Sessions with Long-Idle
Transactions To Be Terminated
u 오래 기다리고 있는 세션에 대해서 연결을 기다리지 않고 세션 자동 종료. default: 0
=# SET idle_in_transaction_session_timeout = ’2s’;
=# BEGIN WORK;
-- sit idle for 3 seconds
=# SELECT 1;
FATAL: terminating connection due to idle-in-transaction timeout
server closed the connection unexpectedly

CREATE
EXTENSION
CASCADE
Support
u PostgreSQL 9.6 이전에 EXTENSION 설치 시 종속성 부터 설치
=# create extension cube;
=# create extension earthdistance;
u PostgreSQL 9.6 부터는 EXTENSION의 control 파일에 종속성 정의
=# create extension earthdistance cascade;
NOTICE: installing required extension "cube"
CREATE EXTENSION

CREATE
EXTENSION
CASCADE
Support
# blackhole extension
comment = 'Minimal Extension Template’
default_version = '1.0’
module_pathname = '$libdir/blackhole’
relocatable = true
requires = ’cube, jsonlog’
=# create extension blackhole cascade

SUPPORT
CROSSTABVIEW
IN
PSQL
u PostgreSQL 9.6 이전엔 crosstab 쿼리는 tablefunc 모듈 사용.
=# create table test2 as
select
('{a,b,c,d,e,f}'::text[])[1 + floor(random() * 6)] as type_1,
('{m,n,o,p,q,r}'::text[])[1 + floor(random() * 6)] as type_2,
random() * 1000 as some_float
from generate_series(1,20000);

SUPPORT
CROSSTABVIEW
IN
PSQL
u =# select type_1, type_2, count(*)
from test2 group by type_1, type_2 crosstabview
type_1 | q | n | o | r | m | p
--------+-----+-----+-----+-----+-----+-----
f | 519 | 569 | 515 | 593 | 519 | 560
e | 605 | 539 | 547 | 555 | 587 | 577
c | 574 | 590 | 534 | 549 | 541 | 556
d | 569 | 487 | 569 | 521 | 523 | 553
b | 543 | 594 | 547 | 573 | 548 | 590
a | 586 | 576 | 568 | 555 | 559 | 510
(6 rows)
type_1
|
type_2
|
some_float
-‐-‐-‐-‐+-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐+-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐+-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐
1
|

b

|

m

|409.59995565936
2
|
e

|

n

|453.834847547114
3
|
f

|

o

|113.634209148586
4
|
b

|

n

|332.8404747881
5
|
d

|

n

|832.656755112112
6
|
b

|

o

|525.860982947052
7
|
b

|

r

|873.10529500246

Generic
WAL
facility
u PostgreSQL 9.6은 외부 개발자가 CUSTOM EXTENSION 개발을 쉽게 할
수 있도록 일반화된 WAL 인터페이스 제공
u GenericXLogStart
u GenericXLogRegisterBuffer
u GenericXLogFinish
u GenericXLogAbort

Allow COPY to copy the output of
an INSERT/UPDATE/DELETE ... RETURNING query
=# COPY (INSERT INTO tab_data VALUES (1, 'aa'), (2, 'bb') RETURNING a, b) TO stdout;
1 aa
2 bb
=# COPY (UPDATE tab_data SET b = 'cc' WHERE a = 1 RETURNING *) TO stdout;
1 cc
=# COPY (DELETE FROM tab_data WHERE a = 2 RETURNING *) TO stdout;
2 bb

Prompt variable to show PId of backend
u psql 프롬프트에 Postmaster PID 표시
u 주의) pg_bouncer, pg_pool 등 사용시 PID 예측 불가
=# set PROMPT1 '%n@%/ : %p $ '
depesz@depesz : 26853 $
u prompt에 사용 가능한 모든 옵션:
u https://www.postgresql.org/docs/current/static/app-psql.html#APP-PSQL-PROMPTING

Monitoring Features
u Add System Catalog
u Vacuum progress reporting
u pg_config System View
u System view to monitor WAL receiver status
u Modified System Catalog
u pg_stat_activity wait-type reporting
u Add System Function
u pg_control Values Exposed
u Notification queue monitoring

Monitoring Features -
pg_stat_activity wait-type reporting
u PostgreSQL 9.6에서 pg_stat_activity catalog 컬럼 추가
u wait_event_type - The type of event for which the backend is waiting
u wait_event - Wait event name if backend is currently waiting
u The value of wait_event_type column
• LWLockNamed - Waiting by a particular lightweight lock
• LWLockTranche - Waiting by the lightweight lock for the group
• Lock - Waiting by weight lock (LOCK TABLE statement etc)
• BufferPin - PIN waiting for the buffer
u wait_event
• https://www.postgresql.org/docs/9.6/static/monitoring-stats.html

Vacuum progress reporting
u This catalog provides information about the state of the progress of vacuum processing.
This catalog is readable by the general superuser.
Column
Name Data
Type Description

pid integer
Process
ID
of
backend
datid oid OID
of
database
datname name Connected
database
name
relid oid OID
of
the
table
being
vacuumed
phase text Current
processing
phase
of
vacuum
heap_blks_total bigint Total
number
of
heap
blocks
in
the
table
heap_blks_scanned bigint Number
of
heap
blocks
scanned
heap_blks_vacuumed bigint Number
of
heap
blocks
vacuumed
index_vacuum_count bigint Number
of
completed
index
vacuum
cycles
max_dead_tuples bigint Number
of
dead
tuples
that
we
can
store
before
needing
to
perform
an
index

vacuum
cycle
num_dead_tuples bigint Number
of
dead
tuples
collected
since
the
last
index
vacuum
cycle

pg_config System View
u pg_config를 시스템 유저 권한으로 SQL로 조회
u Column: name, setting
postgres=#
SELECT
*
FROM
pg_config
;

name
|
setting
-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐+-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐
BINDIR
|
/usr/local/pgsql/bin
DOCDIR
|
/usr/local/pgsql/share/doc
HTMLDIR
|
/usr/local/pgsql/share/doc
INCLUDEDIR
|
/usr/local/pgsql/include
PKGINCLUDEDIR
|
/usr/local/pgsql/include

pg_control Values Exposed
Name Return
Type Description
pg_control_checkpoint() record
Returns
information
about
current
checkpoint

state.
pg_control_system() record
Returns
information
about
current
control
file
s
tate.
pg_control_init() record
Returns
information
about
cluster
initialization

state.
pg_control_recovery() record Returns
information
about
recovery
state.
They also show information about write-ahead logging and checkpoint processing. This
information is cluster-wide, and not specific to any one database

System view to monitor WAL receiver status
This catalog provides information about the state of a slave instance's WAL receiver
process in replication environment. This catalog is readable by the general user.
pid integer Process ID of the WAL receiver process
status text Activity status of the WAL receiver process
receive_start_lsn pg_lsn
First transaction log position used when WAL
receiver is started
receive_start_tli integer
First timeline number used when WAL receiver is
started
received_lsn pg_lsn
Last transaction log position already received and
flushed to disk, the initial value
received_tli integer
Timeline number of last transaction log position
received and flushed to disk, the initial value
last_msg_send_time timestamp with time zone
Send time of last message received from origin WAL
sender

System view to monitor WAL receiver status (…)
This catalog provides information about the state of a slave instance's WAL receiver
process in replication environment. This catalog is readable by the general user.
pid integer Process ID of the WAL receiver process
last_msg_receipt_time timestamp with time zone
Receipt time of last message received from origin
WAL sender
latest_end_lsn pg_lsn
Last transaction log position reported to origin WAL
sender
latest_end_time timestamp with time zone
Time of last transaction log position reported to
origin WAL sender
slot_name text Replication slot name used by this WAL receiver
conninfo text
Connection string used by this WAL receiver, with
security-sensitive fields obfuscated.

Notification queue monitoring
u PostgreSQL 큐는 8GB까지의 제한 존재
u DBA 관리자가 큐에 남은 작업이 있는지 확인할 필요
=# select pg_notification_queue_usage();
u 이 함수가 반환하는 실수 양에 따라 남아있는 작업량 판단 가능

PostgreSQL 9.6 새 기능 소개

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PostgreSQL 9.6 새 기능 소개