Postgres DB demo

Table of content:

Postgres DB demo
- Reference:
  - Guidelines
  - install DB
- PG features
  - connect local
  - Json support
  - Server push
  - Table inherit
  - PARTITION 拆分表: postgreSQL 10
  - postgres_fdw 外包装数据
  - Hash，GIN, BRIN index
  - Array type 数组类型， range 区间类型

Reference:

Guidelines

============ env ============
PG_HOME=/global/ocean/data/ocean/postgre
PG_BIN=$PG_HOME/current/bin
PGLOG=$PG_HOME/data/logs/pg96
PGLOG_FILE=$PGLOG/postgre_server.log
PGDATA=$PG_HOME/data/pg96

============ control ============
${PG_BIN}/initdb -U $PGUSER -W    #run once 

${PG_BIN}/pg_ctl -l $PGLOG_FILE start   
#${PG_BIN}/pg_ctl -l $PGLOG_FILE  -o "-F -p 5480" start 
${PG_BIN}/pg_ctl -l $PGLOG_FILE restart 
${PG_BIN}/pg_ctl   status
${PG_BIN}/pg_ctl -l $PGLOG_FILE  stop -m fast

============ create  ============
${PG_BIN}/createdb -O $PGUSER  $PGDATABASE
${PG_BIN}/createuser -P -E -e $PGUSER

${PG_BIN}/dropuser $PGUSER
${PG_BIN}/dropdb  $PGDATABASE

============ login psql ============
psql -U username -h hostname -p port -d dbname

PGUSER=admin
PGPASSWORD=password
PGDATABASE=meta_int

============ ops in psql =============
help: \h
quit: \q

list DB: \l
list tables: \dt *.* (all table of all schema)
list index: \di
lsit schema: \dn

switch DB: \c dbname:
desc table: \d tblname

alter table [tblname] add column [col_name] [type];

install DB

// find rpm
ls -lt /net/stealth.nj.ssmb.com/export1/home1.localhost/sw/Linux | grep -i postgre 
// install
rpm -ivh postgresql96-libs-9.6.15-1PGDG.rhel6.x86_64.rpm
rpm -ivh postgresql96-9.6.15-1PGDG.rhel6.x86_64
rpm -ivh postgresql96-server-9.6.15-1PGDG.rhel6.x86_64

ln -s /usr/pgsql-9.6/bin $PG_HOME/current

// config file:
$PGDATA\pg_hba.conf
$PGDATA\postgresql.conf

// uninstall
rpm -e postgresql96-server-9.6.15-1PGDG.rhel6.x86_64

PG features

connect local

connect by vscode sqltools:

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jdbc_url：jdbc:postgresql://oceanap02d.nam.nsroot.net:5432/meta_int
url: postgresql://oceanap02d.nam.nsroot.net:5432/meta_int

username: admin
password: password

Json support

there are 2 types to save json data:

Json type: will save as document 
Jsonb type: has only useful value for higher performance (GIN index)

Jsonb/Json query ops

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Jsonb specially supported query

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example

-- @block return json object
select '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json->'tags' as tags;

-- @block return text
select '{"foo": [true, "bar"], "tags": {"a": 1, "b": null}}'::json->>'tags' as tags;

-- @block path select: will return "bar"
select '{"a": [1, "bar", 2], "tags": {"a": 1, "b": null}}'::json#>'{a,1}';

-- @block contain value
select '{"nickname": "gs", "avatar": "avatar_url", "tags": ["python", "golang", "db"]}'::jsonb @> '{"nickname": "gs"}'::jsonb;
--select '{"nickname": "gs", "avatar": "avatar_url", "tags": ["python", "golang", "db"]}'::jsonb->'nickname' = '"gs"';

-- @block select content of accounts_jsonb
-- @conn PGSQL
select content from test.accounts_jsonb

-- @block contain nickname = 'cowww'
-- @conn PGSQL
select content from test.accounts_jsonb where content @> '{"nickname" : "cowww"}'

-- @block select content tags contain 'scala'
-- @conn PGSQL
select content from test.accounts_jsonb where content::jsonb->'tags' ? 'scala'

-- @block map normal row to json object
select row_to_json(company) from public.company;

more details refer to: here

Server push

可以将关于特定主题的消息广播给正在监听该主题的所有连接订户。
消息由Postgres服务器推送到侦听客户端。不需要轮询，
但您的数据库驱动程序应支持异步向应用程序传递通知。

-- create a listener on a channel
LISTEN 'my_channel';

-- send message to channel
NOTIFY 'my_channel', 'my message text';


-- 结合 trigger 触发器 pg_notify:

SELECT pg_notify('foo_events', '{"userid":42,"action":"grok"}');

Java client


connection.notificationHandler(notification -> {
  System.out.println("Received " + notification.getPayload() + 
  " on channel " + notification.getChannel());
});

connection.query("LISTEN some-channel", ar -> {
  System.out.println("Subscribed to channel");
});

Table inherit

example

CREATE TABLE invoices (
    invoice_number   int  NOT NULL PRIMARY KEY,
    issued_on        date NOT NULL DEFAULT now()
);

CREATE TABLE government_invoices (
    department_id    text NOT NULL
) INHERITS (invoices);

PARTITION 拆分表: postgreSQL 10

将一个逻辑的大表，分割成物理的小表。从而获得几点优势：

1.提高查询性能，特别是对于某些只落在某一段区间的查询；分块可以减少索引的大小，从而可以全部放在内存中

2.当查询访问某一块的大部分数据时，原来需要随机访问的，现在可以seq scan；避免随机扫描

3.块操作（加载或者删除）都可以直接对partition操作
ALTER TABLE DETACH PARTITION或者直接 DROP TABLE）进行处理，避免了vacuum的负载

4.冷热数据分离存储

CREATE TABLE measurement (
    city_id         int not null,
    logdate         date not null,
    peaktemp        int,
    unitsales       int
) PARTITION BY RANGE (logdate);

CREATE TABLE measurement_y2008m01 PARTITION OF measurement
    FOR VALUES FROM ('2008-01-01') TO ('2008-02-01')
    WITH (parallel_workers = 4)
    TABLESPACE fasttablespace;

CREATE TABLE measurement_y2006m02 PARTITION OF measurement
    FOR VALUES FROM ('2006-02-01') TO ('2006-03-01');

CREATE TABLE measurement_y2006m03 PARTITION OF measurement
    FOR VALUES FROM ('2006-03-01') TO ('2006-04-01');

postgres_fdw 外包装数据

Hash，GIN, BRIN index

Array type 数组类型， range 区间类型

https://www.kancloud.cn/hfpp2012/postgresqlbook/467209

pg readme