欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

PostgreSQL 9.4版本的物化视图更新

程序员文章站 2022-05-11 09:14:46
...

PostgreSQL的9.4版本出来有一段时间了,也更新了很多内容,其中之一是比较感兴趣的物化视图的更新,对比原先的物化视图语法,新增

PostgreSQL的9.4版本出来有一段时间了,也更新了很多内容,其中之一是比较感兴趣的物化视图的更新,对比原先的物化视图语法,新增了一个CONCURRENTLY参数。

一、新语法:

--创建语法,未有更新 CREATE MATERIALIZED VIEW table_name [ (column_name [, ...] ) ] [ WITH ( storage_parameter [= value] [, ... ] ) ] [ TABLESPACE tablespace_name ] AS query [ WITH [ NO ] DATA ] --刷新语法 REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] name [ WITH [ NO ] DATA ]

二、数据准备:

[postgres@ ~]$ psql psql (9.4.1) Type "help" for help. postgres=# create table tbl_kenyon(id int,remark text); CREATE TABLE postgres=# insert into tbl_kenyon select generate_series(1,1000000),md5(random()::text); INSERT 0 1000000 postgres=# select * from tbl_kenyon limit 10; id | remark ----+---------------------------------- 1 | d4fc1c7440a4d1672028586c2bb76514 2 | 5c1590519fa47f02db2895146a5f62a4 3 | 1710ac4199746e9bfa188f1655d1f857 4 | 6cae64191c2bc309a4884301e77b26ad 5 | 813987a5c3af2d75bd0de6e288083b10 6 | c52baa42cda22c89719bfb59dde1f78b 7 | 491003337ea4e887c5ac24d174c691c6 8 | 455cdf32b170fcf2b450c0b974fbf310 9 | 43adb30aeb0a21ab35fdf97064ad1d21 10 | 97dc1adc5484244a077e87ef36ecfe09 (10 rows) --创建简单的物化视图 postgres=# create materialized view mv_tbl_kenyon as select * from tbl_kenyon ; SELECT 1000000 postgres=# \d+ List of relations Schema | Name | Type | Owner | Size | Description --------+---------------+-------------------+----------+-------+------------- public | mv_tbl_kenyon | materialized view | postgres | 65 MB | public | tbl_kenyon | table | postgres | 65 MB | (2 rows)

三、测试用例:

--测试不带concurrently postgres=# insert into tbl_kenyon values(1000001,md5(random()::text)); INSERT 0 1 postgres=# select max(id) from mv_tbl_kenyon ; max --------- 1000000 (1 row) postgres=# \timing Timing is on. postgres=# refresh materialized view mv_tbl_kenyon ; REFRESH MATERIALIZED VIEW Time: 2056.460 ms --测试带concurrently,需要建一个唯一索引 postgres=# insert into tbl_kenyon values(1000002,md5(random()::text)); INSERT 0 1 Time: 9.434 ms postgres=# refresh materialized view concurrently mv_tbl_kenyon; ERROR: cannot refresh materialized view "public.mv_tbl_kenyon" concurrently HINT: Create a unique index with no WHERE clause on one or more columns of the materialized view. Time: 22109.877 ms postgres=# create unique index idx_ken on mv_tbl_kenyon(id); CREATE INDEX Time: 707.721 ms postgres=# select max(id) from mv_tbl_kenyon ; max --------- 1000001 (1 row) Time: 1.110 ms postgres=# begin; BEGIN postgres=# refresh materialized view concurrently mv_tbl_kenyon; REFRESH MATERIALIZED VIEW Time: 24674.739 ms --如果在refresh的时候,前面加个begin; --还能发现在开启的另外的session里面,是不会阻塞查询的,反之不加concurrently会阻塞 postgres=# select * from mv_tbl_kenyon limit 10; id | remark ----+---------------------------------- 1 | d4fc1c7440a4d1672028586c2bb76514 2 | 5c1590519fa47f02db2895146a5f62a4 3 | 1710ac4199746e9bfa188f1655d1f857 4 | 6cae64191c2bc309a4884301e77b26ad 5 | 813987a5c3af2d75bd0de6e288083b10 6 | c52baa42cda22c89719bfb59dde1f78b 7 | 491003337ea4e887c5ac24d174c691c6 8 | 455cdf32b170fcf2b450c0b974fbf310 9 | 43adb30aeb0a21ab35fdf97064ad1d21 10 | 97dc1adc5484244a077e87ef36ecfe09 (10 rows)

四、源码
相关唯一索引的源码,在matview.c里面可以查看:

--先初始化唯一索引是false foundUniqueIndex = false; --如果找到唯一索引赋值为true if (foundUniqueIndex) appendStringInfoString(&querybuf, " AND "); colname = quote_identifier(NameStr((tupdesc->attrs[attnum - 1])->attname)); appendStringInfo(&querybuf, "newdata.%s ", colname); type = attnumTypeId(matviewRel, attnum); op = lookup_type_cache(type, TYPECACHE_EQ_OPR)->eq_opr; mv_GenerateOper(&querybuf, op); appendStringInfo(&querybuf, " mv.%s", colname); foundUniqueIndex = true; --如果找不到唯一索引报error if (!foundUniqueIndex) ereport(ERROR,(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("cannot refresh materialized view \"%s\" concurrently",matviewname), errhint("Create a unique index with no WHERE clause on one or more columns of the materialized view."))); appendStringInfoString(&querybuf, " AND newdata OPERATOR(pg_catalog.*=) mv) " "WHERE newdata IS NULL OR mv IS NULL " "ORDER BY tid");

五、总结:
1.新版的物化视图新增了concurrently参数,可以使在刷新视图时不会锁住该物化视图的查询工作
2.该参数的原理和优缺点与索引的concurrently类似,以时间来换取查询锁,,刷新的速度会变得很慢
3.增量刷新的参数还没有,比较遗憾

------------------------------------华丽丽的分割线------------------------------------

CentOS 6.3环境下yum安装PostgreSQL 9.3

PostgreSQL缓存详述

Windows平台编译 PostgreSQL

Ubuntu下LAPP(Linux+Apache+PostgreSQL+PHP)环境的配置与安装

Ubuntu上的phppgAdmin安装及配置

CentOS平台下安装PostgreSQL9.3

PostgreSQL配置Streaming Replication集群

如何在CentOS 7/6.5/6.4 下安装PostgreSQL 9.3 与 phpPgAdmin

------------------------------------华丽丽的分割线------------------------------------

PostgreSQL 的详细介绍:请点这里
PostgreSQL 的下载地址:请点这里

本文永久更新链接地址