hoon

INSERT에서 shared lock을 거는 이유 질문

<blockquote>MySQL 서버에 연결된 컨넥션중에서 해당 테이블을 사용하는 컨넥션의 개수만큼 해당 메모리 공간 예약이 필요합니다.</blockquote>그렇군요 😃<blockquote>내부적으로 테이블을 리빌드하며, 온라인으로 컬럼 추가가 불가능합니다.</blockquote>default를 표현식으로 추가하는 경우는 instant로 컬럼추가가 불가능하군요. 신기하네요.<blockquote>TEXT 타입은 항상 오프페이지로 저장되는 것은 아닙니다. 하나의 레코드 사이즈가 데이터페이지의 절반 크기보다 작은 경우 가변길이 컬럼의 값은 기존 다른 컬럼들과 함께 동일한 데이터페이지에 저장됩니다.</blockquote>text는 왜 row사이즈 제한(64KB)에 포함안되는지는 잘 이해가 안되네요. text나 varchar 둘다 오프페이지로도 저장될 수 있고 저장될 수 있어서 비슷한거같은데.. <a target="_blank" rel="noopener noreferrer nofollow" href="https://dev.mysql.com/doc/refman/8.0/en/column-count-limit.html#row-size-limits">https://dev.mysql.com/doc/refman/8.0/en/column-count-limit.html#row-size-limits</a> 공식문서에도 이유는 안나와있군요 🤔 근데 프로그램이 다 이유가 있는 동작만 하는건 아니니 그냥 그러려니..&nbsp;답변 감사합니다.좀더 찾아보니 성욱님이 적으신 블로그글에 제 질문과 관련된 내용들이 많이 나오네요.<a target="_blank" rel="noopener noreferrer nofollow" href="https://medium.com/daangn/varchar-vs-text-230a718a22a1">https://medium.com/daangn/varchar-vs-text-230a718a22a1</a>

(1,2강) char, varchar, text 관련 질문

5번은 <a target="_blank" rel="noopener noreferrer nofollow" href="https://www.inflearn.com/questions/1305027/text-%ED%83%80%EC%9E%85-%EB%8D%B0%EC%9D%B4%ED%84%B0%EA%B0%80-%EC%A0%80%EC%9E%A5%EB%90%98%EB%8A%94-%EC%9C%84%EC%B9%98%EC%97%90-%EB%8C%80%ED%95%B4-%EC%A7%88%EB%AC%B8%EB%93%9C%EB%A6%BD%EB%8B%88%EB%8B%A4">https://www.inflearn.com/questions/1305027/text-%ED%83%80%EC%9E%85-%EB%8D%B0%EC%9D%B4%ED%84%B0%EA%B0%80-%EC%A0%80%EC%9E%A5%EB%90%98%EB%8A%94-%EC%9C%84%EC%B9%98%EC%97%90-%EB%8C%80%ED%95%B4-%EC%A7%88%EB%AC%B8%EB%93%9C%EB%A6%BD%EB%8B%88%EB%8B%A4</a>여기에 질문이 있군요.

그리고 보통 어떨때 임베디드를 쓰고 어떨떄 이너클래스를 따로 만드는지 용도의 주 사용처가 궁금합니다!

이너클래스로 새로운 엔티티! 와 임베디드 차이?

동시성 떄문에 세션에 concurrenthashmap 쓰는것에 대한 질문입니다.

세션에서 동시성 이슈가 발생할수 있다고 하셨는데

<pre><code>spring:
 config:
 activate:
 on-profile: local
 datasource:
 url: "jdbc:h2:mem:balance;MODE=MYSQL;NON_KEYWORDS=USER"
 username: "sa"
 password: ""
 driver-class-name: org.h2.Driver
 jpa:
 hibernate:
 ddl-auto: create
 properties:
 hibernate:
 format_sql: true
 show_sql: true
 dialect: org.hibernate.dialect.H2Dialect
 open-in-view: false
 h2:
 console:
 enabled: true
 path: /h2-console

server:
 port: 8081


---

spring:
 config:
 activate:
 on-profile: dev
 datasource:
 url: "jdbc:mysql://localhost/balance"
 username: "root"
 password: "Abcd1234!"
 driver-class-name: com.mysql.cj.jdbc.Driver
 jpa:
 hibernate:
 ddl-auto: none
 properties:
 hibernate:
 format_sql: true
 show_sql: true
 dialect: org.hibernate.dialect.MySQL8Dialect
 open-in-view: false


server:
 port: 8081</code></pre>와 같고 dev 로 실행시켰고 mysql 안에 balance 에는 테이블과 정보를 새로 넣어두었습니다

배포해서 서버접속하는것까지 성공하였습니다

깃에 공부한거 정리하며 올리는중인데

<pre class="hljs"><code>
dependencies {
 implementation 'org.springframework.boot:spring-boot-starter-web'
 } 를 추가하였더니 정상작동합니다 이유가 뭔가요????</code></pre>

프로젝트 실행이 안돼요

/Library/Java/JavaVirtualMachines/jdk-11.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA <a target="_blank" rel="noopener noreferrer nofollow" href="http://CE.app/Contents/lib/idea_rt.jar=63069:/Applications/IntelliJ">CE.app/Contents/lib/idea_rt.jar=63069:/Applications/IntelliJ</a> IDEA <a target="_blank" rel="noopener noreferrer nofollow" href="http://CE.app/Contents/bin">CE.app/Contents/bin</a> -Dfile.encoding=UTF-8 -classpath /Users/kimyunsoo/Downloads/jdbc 7/out/production/classes:/Users/kimyunsoo/Downloads/jdbc 7/out/production/resources:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework.boot/spring-boot-starter-jdbc/2.7.5/b57c3f8fb2fe235a8ff368755092371423bbc5b3/spring-boot-starter-jdbc-2.7.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework.boot/spring-boot-starter/2.7.5/c28e1546461803490588085345ba5d2897d232bc/spring-boot-starter-2.7.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/com.zaxxer/HikariCP/4.0.3/107cbdf0db6780a065f895ae9d8fbf3bb0e1c21f/HikariCP-4.0.3.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-jdbc/5.3.23/c859919a644942822e49cb7f2404b2c4d3cba040/spring-jdbc-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework.boot/spring-boot-autoconfigure/2.7.5/96646e63a2296d0a3209383e81cdb8c87ab2f913/spring-boot-autoconfigure-2.7.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework.boot/spring-boot/2.7.5/fd04e228e6e21b7ad13c10ae29afd31868d842e5/spring-boot-2.7.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework.boot/spring-boot-starter-logging/2.7.5/61f4c53e35baa31a269bbeb7bb9d5e781448feef/spring-boot-starter-logging-2.7.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/jakarta.annotation/jakarta.annotation-api/1.3.5/59eb84ee0d616332ff44aba065f3888cf002cd2d/jakarta.annotation-api-1.3.5.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-core/5.3.23/91407dc1106ea423c44150f3da1a0b4f8e25e5ca/spring-core-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.yaml/snakeyaml/1.30/8fde7fe2586328ac3c68db92045e1c8759125000/snakeyaml-1.30.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-api/1.7.36/6c62681a2f655b49963a5983b8b0950a6120ae14/slf4j-api-1.7.36.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-tx/5.3.23/ab313b4028c62e18fe02defdd5050af704778428/spring-tx-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-beans/5.3.23/3bdefbf6042ed742cbe16f27d2d14cca9096a606/spring-beans-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-context/5.3.23/530b36b2ce2c9e471c6a260c3f181bcd20325a58/spring-context-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-classic/1.2.11/4741689214e9d1e8408b206506cbe76d1c6a7d60/logback-classic-1.2.11.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.apache.logging.log4j/log4j-to-slf4j/2.17.2/17dd0fae2747d9a28c67bc9534108823d2376b46/log4j-to-slf4j-2.17.2.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.slf4j/jul-to-slf4j/1.7.36/ed46d81cef9c412a88caef405b58f93a678ff2ca/jul-to-slf4j-1.7.36.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-jcl/5.3.23/3c7eb5fcca67b611065f73ff4325e398f8b051a3/spring-jcl-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-aop/5.3.23/30d0034ba29178e98781d85f51a7eb709a628e9b/spring-aop-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.springframework/spring-expression/5.3.23/3a676bf4b9bc42bd37ab5ad264acb6ceb63397a2/spring-expression-5.3.23.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-core/1.2.11/a01230df5ca5c34540cdaa3ad5efb012f1f1f792/logback-core-1.2.11.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/org.apache.logging.log4j/log4j-api/2.17.2/f42d6afa111b4dec5d2aea0fe2197240749a4ea6/log4j-api-2.17.2.jar:/Users/kimyunsoo/.gradle/caches/modules-2/files-2.1/com.h2database/h2/2.1.214/d5c2005c9e3279201e12d4776c948578b16bf8b2/h2-2.1.214.jar hello.jdbc.JdbcApplication . ____ _ /\\ / ___'_ __ (_)_ _ \ \ \ \( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \ \\/ ___)| |_)| | | | | || (_| | ) ) ) ) ' |____| .__|_| |_|_| |_\__, | / / / / =========|_|==============|___/=/_/_/_/ :: Spring Boot :: (v2.7.5)2023-08-04 11:11:53.900 INFO 59660 --- [ main] hello.jdbc.JdbcApplication : Starting JdbcApplication using Java 11.0.18 on gim-yeonsuui-MacBookAir.local with PID 59660 (/Users/kimyunsoo/Downloads/jdbc 7/out/production/classes started by kimyunsoo in /Users/kimyunsoo/Downloads/jdbc 7)2023-08-04 11:11:53.903 INFO 59660 --- [ main] hello.jdbc.JdbcApplication : No active profile set, falling back to 1 default profile: "default"2023-08-04 11:11:54.570 INFO 59660 --- [ main] hello.jdbc.JdbcApplication : Started JdbcApplication in 0.908 seconds (JVM running for 1.132)Process finished with exit code 0&nbsp;이렇게 뜨고 바로 꺼집니다 ㅠㅠ

<pre class="hljs"><code>MvcMemberFormServlet 를 비워뒀더니 그런거였네요
근데 왜 비워두면 오류가 나면서 저런페이지가 뜨는건가요?? 
ServletApplication 가 시작의 기준아닌가요??</code></pre>

hoon

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