yarn uninstall

yarn remove xxx

yarn add xxxx

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Docker not found when freshly installed on Mac

- Docker Desktop -> Settings -> Advanced -> Choose System, not User -> Click [Apply & restart]

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Arrow function vs Function declaration

1. arrow function can not use this
2. arrow function must be defined before use
3. Function declaration can use new 

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spring boot test,spring context

1. get value from application.yaml
1. use environment
2. use profile
3. @component
1. component scan 
2. initialize the component
3. add it to spring application context
4. can get the bean from application context
5. @Component equals @Bean in a @Configuration
4. can use @SpringBootTest to load spring application context 
2. 
   

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after add ports to runing docker container

have to re-create container

docker-compose up -d --force-recreate xxx

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git,commit,branch ,cherry-pick ,merge

• commit 
• is snapshot of all files
• not a change set
•  to store the hash ID of the latest commit in a branch name.
• branch name is just the lastest hash of commi branch name is just the lastest hash of commit
• In fact, this is the very definition of a branch name: a name like master simply stores the hash ID of the commit we want to call the latest for that branch. So given the A--B--C string of commits, we just add the name master, pointing to commit C:

• To remember which branch we want Git to update, as well as which commit we have checked-out right now, Git has the special name HEAD
• current branch
• A--B--C--D <-- develop (HEAD), master
• HEAD still names the current commit.
• A detached HEAD just means that Git has made the name HEAD point directly to some commit instead of attaching it to a branch name

• git merge
• git checkout master
• set HEAD to master
• git merge develop
• go backwards from master and develop, to find a shared base commit (祖先), called merge base
• The merge base commit is determined entirely by the commit graph,
• git diff baseCommint master  => get change set 1 
• git diff basecommit  develop   => get change set 2
• git combine the difference , use  a new commit id to save the result  ( merge commit )
• cherry-pick
• git diff somecommitId to get the change set
• just put the change on current commit(branch)
• but it maybe not works very well, git use cherry-pick-style merge, force the merge base commit to be the parent of the cherry-picked commit.
• cherry-pick create a new commit to save the result. 

•        G--H--F'   <-- master (HEAD)
        /
  ...--D
        \
         E--F   <-- develop

•  cherry-pick uses Git's merge machinery to do the change-combining, but leaves the graph unmerged, simply making a copy of some existing commit

• git merge somecommitid(branch)
• git merge -no-ff

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postgres, golang , sqlx, placeholder, in

sql:  where some_id = any(:some_name)

golang, sqlx: 

 " some_name" :  pg.StringArray([]string )

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vscode ,gvm ,GOROOT

gvm install go19.2
gvm list
gvm use go19.2 --default

=>GOROOT、GOPATH　will be set by gvm automatically

vsCode　will use the go defined by $GOROOT

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kotest -

 "someContainer " - {

 "someTest" { }

 "someTest" { }

}

- はContainerの意味であり、その中に、別のScopeが必要

ない場合は、実行されない。

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mysql explain select

 ## explain select

- access_type:

- all(全件検索)/index(indexの全件検索)はfull-scanであり、要注意。

- indexはallより良い。

- possible_keys: 使用可能なindex(primary-key is index)

- key: 実際使ったindex

- ref: indexのKeyと比較するcolumn

- patition: 使ったpatition. patationは何？大きなテーブルを分解すること

- patitionは使えるかも！

- 分解のtypeは：RANGE,LIST,HASH,KEY

- rows: 大体の件数を推測した結果

- filtered: 条件が効いて、次の層に行く件数の割合。小さい方が良い。

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