From ef61fbf8ebaceaca14528895c64536eb2c07dd4f Mon Sep 17 00:00:00 2001 From: Rawley Date: Thu, 30 Nov 2023 15:13:29 -0600 Subject: [PATCH] Add article about jpa --- jpa-hibernate-stupid-performance.html | 62 +++++++++++++++++++++++++++ trying-lite-xl.html | 17 ++++++++ 2 files changed, 79 insertions(+) create mode 100644 jpa-hibernate-stupid-performance.html create mode 100644 trying-lite-xl.html diff --git a/jpa-hibernate-stupid-performance.html b/jpa-hibernate-stupid-performance.html new file mode 100644 index 0000000..a489662 --- /dev/null +++ b/jpa-hibernate-stupid-performance.html @@ -0,0 +1,62 @@ + + + + Achieving Stupid Performance with JPA and Hibernate + + + +
+ << back +

JPA is slow, lets make it stupid fast

+

+ JPA is not performant. Mainly because of things like batching, and this incessant idea that + querying relationships lazily is somehow fast, its literally just deferring the work, which makes sense + if you potentially don't want to use the data, but most people want that data anyways, or serialize it. +

+

+ I experienced this recently with a massive data set, this database was 1 core table of 4 million rows, followed by multiple child One-To-Many table + of close to 10 million rows, and a single One-to-One with ~4 million rows as well. To use the service built on top of this massive data, you had to search + with JPA search specifications, which turns out also to be insanely slow. The benchmark starts us at 15 or so minutes, which is obviously unacceptable. +

+

Time to go fast

+

+ By enabling 

logging.level.org.hibernate.SQL=DEBUG
and 
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE
, + you're able to see the ridiculous number queries JPA is executing, they're un-countable, there's so many!! How can we fix this? +

+

+ If you're thinking of using 

@Batch(100)
, it could work, only issue is JPA will batch each relationship, so each of our tables will still require + 
n/100
calls where 
n
is the number of rows with relationships. So theoretically a 100x speed bump right? Well, it's actually more + like a 33x performance bump, since you still have the overhead of making the database connections, and need to get a lock every time you select. Doing this we moved to around + 3-5 minutes depending on load per large call. This however, was still unacceptable. +

+

+ What if instead we just forced JPA to use 

OUTER JOIN
? Isn't that exactly what the ANSI SQL wizards would tell you to do? + Obviously, this is the solution, one single connection, 1 lock, and let the B-Tree optimizations inside of the database handle all of this ugliness for us. + To do this you need to use something called 
@EntityGraph
 + on your JPA repository, what this does is forces JPA to use a 
OUTER JOIN
+ to join relationships. This even works on nested entities, say I have Entity A with a child B which also has a One-to-Many on C, all you need to do + is add the relationship to the entity graph with the 
@NamedEntityGraph
annotation, then provide it with a few nice args like name, + and attributeNodes which will point to your sub entity. Then finally on your JPA repository call you stitch the entity graph back together. +

+

+ 

+                
+@Repository
+public interface ARepository extends JpaRepository, JpaSpecificationExecutor {
+    @Override
+    @EntityGraph(attributePaths = { "bs", "B.cs" }) // Where B's are children of A's, and C's are children of B's.
+    Page findAll(@Nullable Specification specification, Pageable pageable);
+}
+                
+
+

+

+ After applying these, the query time went down from 15 minutes to ... *drum-roll* ... 3 seconds. So please, for the love of all that is computationally efficient, force your JPA + to use 

OUTER JOIN
, or even roll your own SQL, ORM's really are one of the biggest trade-offs, and they really can bite you. This is why tend to + stay in the 
DBI
universe when I write Perl. It's funny shocking Ruby on Rails and Java developers with my ~15ms queries :D +

+
+
+
+ + diff --git a/trying-lite-xl.html b/trying-lite-xl.html new file mode 100644 index 0000000..32979dd --- /dev/null +++ b/trying-lite-xl.html @@ -0,0 +1,17 @@ + + + Running mod_perl with Mojolicious in Docker + + + + + +
+ << back +

Trying Lite-XL

+

+ +

+
+ +