最近逛书店，看到了《太平洋战争三部曲》，翻看了之后觉得很有兴趣继续读，就下载到kindle上继续阅读，断断续续的把三本快要看完了，中间又穿插着看了美剧《太平洋战争》，和书对照，里面有些互相引证的部分。美剧中的是以美军普通士兵的视角来看待太平...
Clickhouse Thinking
列存储 https://clickhouse.com/docs/knowledgebase/key-value ch的列存储，每一列是独立的文件存储，select * from test where k = 1 limit 10的查询，如果k是order by的列，那么查找会很快速的定位到文件，然后文件内查找定位到行，然后就得到所在文件的行数，之后再去找其他所有列对应的文件，然后读取对应行...
Clickhouse Projections
确认projection生效： https://clickhouse.com/docs/knowledgebase/projection_example ReadFromPreparedSource (for_column2) 可以看出是走了projection clickhouse-23.12 :) explain indexes = 1 SELECT count() from table1_projections where column2 > 999 and column1 > 1; ┌─explain─────────────────────────────────────┐ │ Expression ((Projection + Before ORDER BY)) │ │ Aggregating │ │ Filter │ │ ReadFromPreparedSource (for_column2) │ └─...
Baby Talk
小朋友快要3岁了，有时候会说一些很有意思的话，这里做一些记录。 我好烦 //闹钟响了 Baby: 什么声音？ Mom： 闹钟的声音 Baby：快把闹钟关掉，我好烦 //妈妈去关闹钟 无中生有 去取快递时 Baby： 是不是我的消防车到了 之前并没有答应过他要买消防车 拆快递时...
Clickhouse Optimize
Query cache https://clickhouse.com/docs/en/operations/query-cache https://clickhouse.com/blog/introduction-to-the-clickhouse-query-cache-and-design v23.1 开始支持Query cache, 即可以缓存查询结果，可以选择针对会话启用。 设置项： query_cache_min_query_runs 查询运行过多少次才会启用缓存 query_cache_min_query_duration 查询运行时间超过多少才会缓存 query_cache_ttl cache 过期时间 query_cache_max_entries 往缓存表中存储的缓存结果条数 use_query_cache 此查询是否使用缓存 enable_reads_from_query_cache 此查询是否先从缓存中读 enable_writes_to_query_cache 此查询的结果...
Clickhouse Deduplication
Deduplication Strategies 笔记 去重操作，CH不是在插入阶段去重，而是插入后，速度会很快，影响: 任何时间，数据中可能会有重复数据 分区合并时，才会去重 查询语句需要适配重复数据 几种合并： ReplacingMergeTree： 相同排序键的会被合并 CollapsingMergeTree: 有一个字段标识取消，可...
Clickhouse MV
《Everything you should know about materialized views.》 阅读笔记 原理 materialized views（以下简称MV）在insert的时候触发，并不会读源表，往一个表insert后，MV会从insert的数据中进行创建。 因此，源表甚至可以是个NULL Engine，即实际不...
Hello 2024
Hello 2024, goodby 2023. In 2024, I wish I’ll write more blog posts, at least one pre week. Last year, I finally got a basement to do some woodworking, and recently I bought a some wood and a lot of woodworking tools, every weekend I will go there and do some woodworking, I only finished a horse bench, three shelfs, wish I will finish one or two tables in 2024.
Zsh eat my curl Output
I got a strange problem today, a URL is supposed to return something in it’s body, but when use curl to get that url, it outputs nothing. curl 'http://localhost:9527/static/a.js' At first, I think it might be server problems, but when using wireshark to see the traffic, there is nothing wrong, http header followed by \r\n then http response body. I have also noticed that this happens when the response body is short. Testing with browser or python-requests is fine. So it’s not the server error, could it be curl’s problem? Let’s strace it. >> strace -vv curl 'http://localhost:9527/static/a.js' ...... recvfrom(5, "HTTP/1.1 200 OK\r\nServer: YNM3K-9"..., 102400, 0, NULL, NULL) = 443 newfstatat(1, "", {st_dev=makedev(0, 0x1d), st_ino=6, st_mode=S_IFCHR|0620, st_nlink=1, st_uid=1000, st_gid=5, st_blksize=1024, st_blocks=0, st_rdev=makedev(0x88, 0x3), st_atime=1703671640 /* 2023-12-27T18:07:20....
Auto open apps on Mac
I poweroff my laptop every night. So I have to open some app I use everyday when I started the laptop. I use a script by Justin Hileman, to open news tabs in terminal. Save this script as init.sh, run sh init.sh in the terminal, and it will do several things: run wg.sh, setup wireguard tunnal open new tab, start a tmux session open new tab, using mosh to ssh a server open new tab, open a txt file using vim open github in chrome start vs code show a popup message #!/bin/bash # # Open new Terminal tabs from the command line # # Author: Justin Hileman (http://justinhileman.com) # # Installation: # Add the following function to your `.bashrc` or `....