high-performance-java-persistence | Performance Java Persistence book and video course code | Object-Relational Mapping library
kandi X-RAY | high-performance-java-persistence Summary
kandi X-RAY | high-performance-java-persistence Summary
The High-Performance Java Persistence book and video course code examples
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high-performance-java-persistence Key Features
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QUESTION
I'm currently reading Vlad Mihalcea's book High-Performance Java Persistence.
In the Bytecode Enhancement section, it is said that enableDirtyTracking can optimize performance with large amounts of data through replacing reflections. But I'm just wondering if there are any disadvantages?
Unfortunately, I couldn't find any or only very old information.
...ANSWER
Answered 2019-Nov-18 at 19:50The enableAssociationManagement only works from parent to child entities, not the other way around. So, it's not very useful. Better synchronize both ends of a bidirectional association.
The enableLazyInitialization can be useful for lazy attributes, as explained in this article.
The enableDirtyTracking setting is not needed if you make sure the Persistence Context never loads too many entities. You are better off reducing the Persistence Context size than using this setting.
The enableExtendedEnhancement setting allow a you to extends more than the entity classes, so bytecode enhancement can work even beyond calling getters and setters on entities. This setting is not recommended.
QUESTION
I have been consulting a number of approaches/posts/stackoverflow questions in order to deal with the following error (full stack trace) when running a Kotlin/SpringBoot application:
...ANSWER
Answered 2020-Apr-25 at 04:11Extending with an example, sorry I know I am a bit late
in your pom.xml:
QUESTION
In High Performance Java Persistence book's 6.3.3.3 section it's written that Lost Update phenomena is possible in MySQL Repeatable Read isolation level. This is the screenshot:
Assuming the following(isolation level is REPEATABLE READ):
...ANSWER
Answered 2019-Nov-18 at 12:27In Repeatable Read isolation level shouldn't MySQL MVCC prevent Lost Update using database level Pessimistic Locking resulting into transaction rollback?
According to the SQL standard, Repeatable Read should prevent:
- dirty reads
- non-repeatable reads
The standard says nothing about lost updates because the standard was designed when 2PL (Two-Phase Locking) was the facto Concurrency Control mechanism.
If you use 2PL, then the Repeatable Read isolation level will, indeed, prevent a Lost Update.
However, MVCC can provide Repeatable Reads via multiple versions of a tuple, but, in order to prevent Lost Updates, they also need the transaction scheduler to track tuple modifications for the records read by a certain transaction. Apparently, InnoDB does not work like that.
shouldn't MySQL MVCC prevent Lost Update using database-level Pessimistic Locking resulting into transaction rollback
Now, if you read carefully the Transactions chapter in my High-Performance Java Persistence book, you will find out that MVCC does not use any Pessimistic Locking in Repeatable Read. The only locks taken are the gap and next-key locks taken on the clustered index, but those don't prevent Lost Updates.
MySQL uses Pessimistic Locking for Serializable only, which provides a 2PL Concurrency Control model, even when using the MVCC_based InnoDB storage engine.
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Install high-performance-java-persistence
PostgreSQL You should install PostgreSQL and the password for the postgres user should be admin. Now you need to create a high_performance_java_persistence database.
Oracle You need to download and install Oracle XE Set the sys password to admin Connect to Oracle using the "sys as sysdba" user and create a new user: alter session set "_ORACLE_SCRIPT"=true; create user oracle identified by admin default tablespace users; grant dba to oracle; alter system set processes=1000 scope=spfile; alter system set sessions=1000 scope=spfile; ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;
MySQL You should install MySQL 8 and the password for the mysql user should be admin. Now, you need to create a high_performance_java_persistence schema Beside having all privileges on this schema, the mysql user also requires select permission on mysql.PROC. If you don't have a mysql user created at database installation time, you can create one as follows: CREATE USER 'mysql'@'localhost'; SET PASSWORD for 'mysql'@'localhost'='admin'; GRANT ALL PRIVILEGES ON high_performance_java_persistence.* TO 'mysql'@'localhost'; GRANT SELECT ON mysql.* TO 'mysql'@'localhost'; FLUSH PRIVILEGES;
SQL Server You should install SQL Server Express Edition with Tools. Chose mixed mode authentication and set the sa user password to adm1n. Open SQL Server Configuration Manager -> SQL Server Network Configuration and enable Named Pipes and TCP In the right pane of the TCP/IP option, choose Properties, then IP Addresses and make sure you Enable all listed IP addresses. You need to blank the dynamic TCP port value and configure the static TCP port 1433 for all IPs. Open SQL Server Management Studio and create the high_performance_java_persistence database
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