PostgreSQL 9.5于2016年1月7日正式发布,此版本主要带来了以下几个方面的特性: UPSERT, Row Level Security, and Big Data
1)UPSERT
UPSERT是INSERT, ON CONFLICT UPDATE的简写,简而言之就是:插入数据,正常时写入,主键冲突时更新。以下给个简单的例子:
--创建测试表,并插入一条数据。
CREATE TABLE customer (cust_id INTEGER PRIMARY KEY, name TEXT); INSERT INTO customer VALUES (100, ’Big customer’); --常规INSERT语句,主键冲突,报错。 INSERT INTO customer VALUES (100, ’Non-paying customer’); ERROR: duplicate key value violates unique constraint "customer_pkey" DETAIL: Key (cust_id)=(100) already exists. --新特性,主键冲突时,自动更新数据。 INSERT INTO customer VALUES (100, ’Non-paying customer’) ON CONFLICT (cust_id) DO UPDATE SET name = EXCLUDED.name; SELECT * FROM customer; cust_id | name ---------+--------------------- 100 | Non-paying customer
2)Row Level Security
行级安全控制,看代码:
--创建测试表,并开启行级别安全策略
CREATE TABLE orders (id INTEGER, product TEXT, entered_by TEXT); ALTER TABLE orders ENABLE ROW LEVEL SECURITY; CREATE POLICY orders_control ON orders FOR ALL TO PUBLIC USING (entered_by = CURRENT_USER); GRANT ALL ON TABLE orders TO PUBLIC; --创建两个用户 CREATE USER emp1; CREATE USER emp2; --分别插入一条数据 SET SESSION AUTHORIZATION emp1; INSERT INTO orders VALUES (101, ’fuse’, CURRENT_USER); SET SESSION AUTHORIZATION emp2; INSERT INTO orders VALUES (102, ’bolt’, CURRENT_USER); --使用超级用户,可以看到所有纪录。 SET SESSION AUTHORIZATION postgres; SELECT * FROM orders; id | product | entered_by -----+---------+------------ 101 | fuse | emp1 102 | bolt | emp2 --普通账号只能看到自己的纪录。 SET SESSION AUTHORIZATION emp1; SELECT * FROM orders; id | product | entered_by -----+---------+------------ 101 | fuse | emp1 SET SESSION AUTHORIZATION emp2; SELECT * FROM orders; id | product | entered_by -----+---------+------------ 102 | bolt | emp2
3)Big Data
3.1)BRIN Indexing
一种占用空间特别小的索引,适合超大数据量且自然排序(如:id递增)的表。
看例子:
CREATE TABLE brin_example AS SELECT generate_series(1,100000000) AS id; CREATE INDEX btree_index ON brin_example(id); CREATE INDEX brin_index ON brin_example USING brin(id); SELECT relname, pg_size_pretty(pg_relation_size(oid)) FROM pg_class WHERE relname LIKE ’brin_%’ OR relname = ’btree_index’ ORDER BY relname; relname | pg_size_pretty --------------+---------------- brin_example | 3457 MB btree_index | 2142 MB brin_index | 104 kB --以上三行是关键,看大小!!!
3.2)Faster Sorts
使用了一种叫做“abbreviated keys”的算法,使得对varchar(),text和NUMERIC()几种类型排序更快,查询提速2~12倍,索引创建提速20倍。
3.3)CUBE, ROLLUP and GROUPING SETS
聚集函数类sql更好写了,OLAP更方便。代码例子太长,就不贴了。
3.4) Foreign Data Wrappers (FDWs)
外部数据包装,
上代码:
--以前得这个写
CREATE FOREIGN TABLE remote.customers ( id int NOT NULL, name text, company text, registered_date date, expiry_date date, active boolean, status text, account_level text) SERVER dest_server OPTIONS (schema_name 'public'); CREATE FOREIGN TABLE remote.purchases ( id int NOT NULL, purchase_time timestamptz, payment_time timestamptz, itemid int, volume int, invoice_sent boolean) SERVER dest_server OPTIONS (schema_name 'public'); --9.5可以这么写 IMPORT FOREIGN SCHEMA public FROM SERVER dest_server INTO remote; --其他写法 IMPORT FOREIGN SCHEMA public EXCEPT (reports, audit) FROM SERVER dest_server INTO remote; IMPORT FOREIGN SCHEMA public LIMIT TO (customers, purchases) FROM SERVER dest_server INTO remote;
3.5)TABLESAMPLE
方便对数据进行抽样。
上代码:
--抽样10%数据
select * from ts_test tablesample system(10);
PostgreSQL越来越强大了。种种迹象来看(BRUCE MOMJIAN说的),PostgreSQL正在朝着多方向发展:
1)Big data大数据:BRIN的支持,Foreign Data Wrappers支持。
2)Data analytics 数据分析:grouping sets, cube, rollup的支持
3)Large servers :Faster Sorts,Hashing性能改善,多核大内存支持更好,比如:IBM POWER-8, having 24 cores, 192 hardware threads, and 492GB RAM环境下,TPS达到40万。
4)NoSQL:JSONB相关支持,单机性能是MongoDB的好几倍。
以上示例代码来自以下: