I have to design a web application to retrieve data from a huge single table with 40 columns and several thousands of rows for select query and few rows/columns for updation.
Can you please suggest me that for faster performance, use of Hibernate is feasible or not as i only have single table and do not have any joins ?
Or should i use jdbc dao ?
database : sql server 2008
java 7
If you use Hibernate right, there's no problem in fetching an arbitrarily large result set. Just avoid from queries (use select ... from ... queries) and use ScrollableResults. If you use plain JDBC, you'll be able to get started quicker because Hibernate needs to be configured first, you need to write the mapping file, etc. but later on it might pay off since the code you write will be much simpler. Hibernate is very good at taking the boilerplate out of client code.
If you want to retrieve several thousand records and pagination is not possible then It might be a performance issue. Because hibernate will create an object against everyone and store it in its persistence context. If you create too many objects, it uses up a lot of memory. For these type of operations JDBC is better. For similar discussion see Hibernate performance issues using huge databases
Related
I have a Java application where we use spring data JPA to query our oracle database. For one use case, I need to fetch all the records present in the table. Now the table has record count of 400,000 thousand and it might grow in the near future. I don't feel comfortable pulling all records into the JVM since we don't know how large they can be. So, I want to configure the code to fetch specific number of records at a time say 50,000 and process before it goes to next 50,000. Is there a way I can achieve this with JPA? I came across this JDBC property that can be used with hibernate hibernate.jdbc.fetch_size. What I am trying to understand is if I use repository.findAll() returning List<Entity>How can a fetch Size work in this case? because List will have all the entities. I was also looking into repository methods returning Stream<>, not sure if I have to use that. Please do suggest. If there can be better solution for this use case?
Thanks
With JPA you can use the Pagination feature, means you tell the Repository how many result should be present at one page. (E.g. 50 000)
For more information follow up here https://www.baeldung.com/jpa-pagination
I use Spring Data JPA (hibernate) generated queries for fetching data from my Sqlserver. Now i am getting performance related issues in my system.
Load findByLoadId(Integer loadId);
This is the query i am using to get data. This query returns 25 cell data but i only use 5 data from that.
can i use direct native query like
select id,date,createdBy,createdOn,loadName from Load where
loadId=:loadId
but if native query is suggestable then I am having question like Does ORM frameWork reduce performence by getting unneeded data from Database?
By "data cell" I assume that you are referring to database table columns, and not to records. The answer to your question is that yes, ORM frameworks might tend to just do a SELECT * under the hood, which can result in unwanted information being sent across the network to your application. If the JPA repository interface is behaving this way, you may switch to either an explicit JPA query (e.g. using the #Query annotation), or even a native query. Then, just select the columns you want. The issue here is that ORM frameworks map object templates (e.g. classes) to entire database tables. So, the concept of entity implicitly includes every database column. If you go with the option of selecting only certain columns, you may need to do some juggling on the Java side. Note that if the use a JPA query, your code would still, in theory, be database independent.
I have a table with more than 100 columns. We are using spring jdbc in our application.
As there were so many columns in the table, I decided to use BeanPropertyRowMapper for fetching the records from DB. This was to avoid writing the hardcoded column and property names in the code which become difficult to manage.
However, when the application went to performance test, I found that there is significant performance hit due to using BeanPropertyRowMapper. I decide to re-write the code with RowMapper with mapping columns names manually from resultSet to the data object properties. This improved the performance.
My question is, if BeanPropertyRowMapper cannot be used with high number of columns, then how is it helping writing cleaner manageable code.
Is there any other way using JDBC I can achieve performance as well as manageable code?
If I want to fetch million rows in hibernate, how would it work? Will hibernate crash? How can I optimize that.
typically you wouldn't use hibernate for this. If you need to do a batch operation, use sql or the hibernate wrappers for batch operations. There is no way loading millions of records is going to end well for your application. Your app with thrash as the gc runs, or possibly crash. there has to be another option.
If you read one/write one it will probably work fine. Are you sure this the way you want to read 1,000,000 rows? It will likely take a while.
If you want all the objects to be in memory at the same time, you might well be challenged.
You can optimize it best, probably, by finding a different way. For example, you can dump from the database using database tools much more quickly than reading with hibernate.
You can select sums, maxes, and counts in the database without returning a million rows over the network.
What are you trying to accomplish, exactly?
For this you would be better off using spring's jdbc tools with a row handler. It will run the query and then perform some action on a row at a time.
Bring only the columns you need. Try it out in a test environment.
You should try looking at the StatelessSession interface and example of which can be found here:
http://mrmcgeek.blogspot.com/2010/09/bulk-data-loading-with-hibernate.html
I need to use an Entity framework with my application, and I have used table - partitions in Oracle database. With simple JDBC, I am able to select data from a specific partition. But I don't know whether I can do the same with hibernate or Eclipse link (JPA). If someone knows how to do that, please do let me know.
usually the select statement in JDBC - SQL is,
select * from TABLE_NAME partiton(PARTITON_NAME) where FIELD_NAME='PARAMETER_VALUE';
How can I do the same with Hibernates or JPA?
Please share at least a link for learning sources.
Thanks!!!
JPA or any other ORM framework does not support Oracle partition tables natively (atleast in my knowledge).
There are different possible solutions though, depending on the nature of your problem:
Refactor your classes so that data that needs to be treated differently in real-life, belongs in a separate class. Sometimes this is called vertical partitioning (partitions are not obtained across rows, rather across columns).
Use Oracle partition tables underneath and use native SQL queries or stored procedures from JPA. This is just a possibile solution (I haven't attempted this).
Use Hibernate Shards. Although the typical use case for Hibernate Shards is not for a single database, it presents a singular view of distributed databases to an application developer.
Related:
JPA Performance, Don't Ignore the Database
EclipseLink supports partitioning or sharding with different options.
You can find more about this and examples here:
http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Advanced_JPA_Development/Data_Partitioning
Table partitioning is data organization on physical level. In a word, partitioning is a poor man index. Like the later, it is supposed to be entirely transparent to the user. A SQL query is allowed to refer to the entire table, but not partition. Then, it is query optimizer job to decide if it can leverage a certain partition, or index.