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 此查询的结果是否写入缓存 Materialized View 物化视图，看这篇 ...

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，可以声明取消前面的数据，然后再插入新数据，多线程写的情况不适用。 VersionedCollapsingMergeTree： 带有版本号的去重，可以 Q： 为什么数据没有被去重？ ...

《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，即实际不写入数据，仅用来在inser时触发MV的动作。 ...

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.

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 /* 2023-12-27T18:07:20.893334033+0800 */, st_atime_nsec=893334033, st_mtime=1703671640 /* 2023-12-27T18:07:20.893334033+0800 */, st_mtime_nsec=893334033, st_ctime=1703662393 /* 2023-12-27T15:33:13.893334033+0800 */, st_ctime_nsec=893334033}, AT_EMPTY_PATH) = 0 brk(0x560907e02000) = 0x560907e02000 rt_sigaction(SIGPIPE, {sa_handler=SIG_IGN, sa_mask=[PIPE], sa_flags=SA_RESTORER|SA_RESTART, sa_restorer=0x7f68b677f710}, NULL, 8) = 0 rt_sigaction(SIGPIPE, {sa_handler=SIG_IGN, sa_mask=[PIPE], sa_flags=SA_RESTORER|SA_RESTART, sa_restorer=0x7f68b677f710}, NULL, 8) = 0 write(1, "a.js", 4a.js) = 4 rt_sigaction(SIGPIPE, NULL, {sa_handler=SIG_IGN, sa_mask=[PIPE], sa_flags=SA_RESTORER|SA_RESTART, sa_restorer=0x7f68b677f710}, 8) = 0 ...... From strace output, I can see it write a.js to fd 1, which is stdout, so it get the response body, and write to stdout, maybe it’s the terminal? ...

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 `.bash_profile`, # or save it somewhere (e.g. `~/.tab.bash`) and source it in `.bashrc` # # Usage: # tab Opens the current directory in a new tab # tab [PATH] Open PATH in a new tab # tab [CMD] Open a new tab and execute CMD # tab [PATH] [CMD] ... You can prob'ly guess function tab () { local cmd="" local cdto="$PWD" local args="$@" if [ -d "$1" ]; then cdto=`cd "$1"; pwd` args="${@:2}" fi if [ -n "$args" ]; then cmd="; $args" fi osascript &>/dev/null <<EOF tell application "iTerm" tell current window set newTab to (create tab with default profile) tell newTab tell current session write text "cd \"$cdto\"$cmd" end tell end tell end tell end tell EOF } function alert(){ title="$1" msg="$2" osascript &>/dev/null <<EOF display notification "$msg" with title "$title" EOF } ~/wg.sh || exit tab "tmux new -s x" tab "mosh root@xxxx" tab "vi notes.txt" open -a "Google Chrome" https://github.com/ code alert "have a nice day"

最近开始用一台旧的XPS 13笔记本，之前被自动升级到了win 11，于是就开始了windows的体验，目前可以使用WSL2，里面安装了ubuntu 22.04, 然后发现了另外一个比较有意思的软件，就是winget, 这个之前一直没有用过，这次就体验了一下。 winget是一个windows的命令行的软件管理器，运行winget update, 它会自动探测系统中已安装的软件版本，然后和数据库中对比，之后就可以选择性的升级。命令行安装或者升级软件还是很方便的，除了部分软件会弹出一个权限确认的窗口外，基本不需要人工交互。这个解决了windows没有软件库的问题，也解决了升级问题。不是所有软件都自身带有自动升级和新版本检测的，比如kicad，不用winget的话，想更新就要自己去官网检查、下载、安装才可以。 ...

不同步某些配置项 参考：https://code.visualstudio.com/docs/editor/settings-sync#_configuring-synced-data 可以设置settingsSync.ignoredSettings, 或者直接在gui上，将“同步此配置”的勾选去掉。比如我可能希望在不同的设备上有不同的主题，就可以配置为 ...

调试ci 参考这篇文章： https://www.lullabot.com/articles/debugging-jobs-gitlab-ci 本地配置gitlab runner环境 在本地代码中操作，修改ci脚本使其在适当的位置sleep 本地提交改动过的代码，注意ci只会执行在git仓库中的代码 运行runner docker exec进入运行中的容器 本地运行runner，注意增加超时时间，避免被杀掉 ...

投影projection 官方文档https://clickhouse.com/docs/en/sql-reference/statements/alter/projection 创建这个特性时的讨论：https://github.com/ClickHouse/ClickHouse/issues/14730 ...