PipelineDB快速上手
PipelineDB是PostgreSQL的一个扩展插件，提供流式数据处理的相关功能。
PipelineDB安装与配置
PipelineDB可以直接通过官方rpm包安装。
加载PipelineDB需要添加动态链接库，在postgresql.conf中修改配置项并重启：
shared_preload_libraries = 'pipelinedb'
max_worker_processes = 128
注意如果不修改max_worker_processes会报错。其他配置都参照标准的PostgreSQL
PipelineDB使用样例 —— 维基PV数据
-- 创建Stream
CREATE FOREIGN TABLE wiki_stream (
hour timestamp,
project text,
title text,
view_count bigint,
size bigint)
SERVER pipelinedb;
-- 在Stream上进行聚合
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;
然后，向Stream中插入数据：
curl -sL http://pipelinedb.com/data/wiki-pagecounts | gunzip | \
psql -c "
COPY wiki_stream (hour, project, title, view_count, size) FROM STDIN"
基本概念
PipelineDB中的基本抽象被称之为：连续视图（Continuous View）。