pipelinedb 初探
pipelinedb的安装：
ref:
http://docs.pipelinedb.com/installation.html#installation
http://docs.pipelinedb.com/quickstart.html#quickstart
说明： pipelinedb 现在已经是pg的一个插件 ，【Since PipelineDB runs as an extension to PostreSQL, begin by installing PostgreSQL】。 我们需要先安装pg，然后安装pipeline的扩展即可
需要先安装postgresql-server11版本
postgresql11-server-11.2-1PGDG.rhel7.x86_64
postgresql11-11.2-1PGDG.rhel7.x86_64
然后，安装对应版本的pipelinedb
rpm -ivh pipelinedb-postgresql-11-1.0.0-13.centos7.x86_64.rpm
# 初始化pg
su - postgres
/usr/pgsql-11/bin/pg_ctl initdb -D /var/lib/pgsql/11/data
修改pg的配置文件
listen_addresses = '*'
max_worker_processes = 128
shared_preload_libraries = 'pipelinedb'
# 启动pg
/usr/pgsql-11/bin/pg_ctl start -D /var/lib/pgsql/11/data
# 登录pg
/usr/pgsql-11/bin/psql
create database pipeline ;
\c pipeline;
create extension pipelinedb;
# 这里还可以有些创建账号、添加pg_hba地址授权等操作，不在本文讨论的范畴内。
/usr/pgsql-11/bin/psql pipeline # 登录后，执行如下的2个SQL：
-- 创建一个外部表，实际数据来自pipelinedb
CREATE FOREIGN TABLE wiki_stream (
hour timestamp,
project text,
title text,
view_count bigint,
size bigint)
SERVER pipelinedb;-- 创建CV视图
CREATE VIEW wiki_stats WITH (action=materialize) AS
SELECT hour, project,
count(*) AS total_pages,
sum(view_count) AS total_views,
min(view_count) AS min_views,
max(view_count) AS max_views,
avg(view_count) AS avg_views,
percentile_cont(0.99) WITHIN GROUP (ORDER BY view_count) AS p99_views,
sum(size) AS total_bytes_served
FROM wiki_stream
GROUP BY hour, project;# 查看数据表：
pipeline=# \d
List of relations
Schema | Name | Type | Owner
--------+------------------+---------------+----------
public | wiki_stats | view | postgres
public | wiki_stats_def | view | postgres
public | wiki_stats_mrel | table | postgres
public | wiki_stats_osrel | foreign table | postgres
public | wiki_stats_seq | sequence | postgres
public | wiki_stream | foreign table | postgres
(6 rows)# 现在我们将数据集解压缩为流并将其写入stdin，它可以用作COPY的输入
curl -sL http://pipelinedb.com/data/wiki-pagecounts | gunzip | /usr/pgsql-11/bin/psql pipeline -c "COPY wiki_stream (hour, project, title, view_count, size) FROM STDIN"
# 查看测试的数据集：
/usr/pgsql-11/bin/psql pipeline -c "SELECT * FROM wiki_stats ORDER BY total_views DESC";
# 要查看系统中当前的连续视图及其定义，可以运行以下查询：
pipeline=# SELECT * FROM pipelinedb.views;
id | schema | name | active | query
----+--------+------------+--------+----------------------------------------------------------------------------------------------------------------------------------
3 | public | wiki_stats | t | SELECT wiki_stream.hour, +
| | | | wiki_stream.project, +
| | | | count(*) AS total_pages, +
| | | | sum(wiki_stream.view_count) AS total_views, +
| | | | min(wiki_stream.view_count) AS min_views, +
| | | | max(wiki_stream.view_count) AS max_views, +
| | | | avg(wiki_stream.view_count) AS avg_views, +
| | | | percentile_cont((0.99)::double precision) WITHIN GROUP (ORDER BY ((wiki_stream.view_count)::double precision)) AS p99_views,+
| | | | sum(wiki_stream.size) AS total_bytes_served +
| | | | FROM wiki_stream +
| | | | GROUP BY wiki_stream.hour, wiki_stream.project
(1 row)pipelinedb 在实时流式计算方面，有很多用法。具体可以参照德哥的github。
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