N+1 queries are a popular problem in many applications that run SQL queries. The problem can be described easily as follows: 1 query fetching a parent value is runN queries fetching each individual child values are run This problem isn't limited to SQL, it can happen with any poorly designed API that does not allow … Continue reading Using jOOQ’s DiagnosticsConnection to detect N+1 Queries
Tag: JDBC
Ad-hoc Data Type Conversion with jOOQ 3.15
jOOQ 3.15 shipped with a ton of new features, the most important ones being: MULTISET support (type safe, nested collections)Reactive SQL support via R2DBC A very useful, lesser known new feature is "ad-hoc data type conversion". Data type converters and bindings have been around in jOOQ for a long time. Their goal is to allow … Continue reading Ad-hoc Data Type Conversion with jOOQ 3.15
Simulating Latency with SQL / JDBC
I've run across a fun little trick to simulate latency in your development environments when testing some SQL queries. Possible use-cases including to validate that backend latency won't bring down your frontend, or that your UX is still bearable, etc. https://twitter.com/gunnarmorling/status/1361061234569805832 The solution is PostgreSQL and Hibernate specific, though to doesn't have to be. Besides, … Continue reading Simulating Latency with SQL / JDBC
How to Run a Bulk INSERT .. RETURNING Statement With Oracle and JDBC
When inserting records into SQL databases, we often want to fetch back generated IDs and possibly other trigger, sequence, or default generated values. Let's assume we have the following table: -- DB2 CREATE TABLE x ( i INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY, j VARCHAR(50), k DATE DEFAULT CURRENT_DATE ); -- PostgreSQL CREATE TABLE … Continue reading How to Run a Bulk INSERT .. RETURNING Statement With Oracle and JDBC
How to Fetch Oracle DBMS_OUTPUT from JDBC
When working with Oracle stored procedures, it is not uncommon to have debug log information available from DBMS_OUTPUT commands. For instance, if we have a procedure like this: CREATE TABLE my_table (i INT); CREATE OR REPLACE PROCEDURE my_procedure (i1 INT, i2 INT) IS BEGIN INSERT INTO my_table SELECT i1 FROM dual UNION ALL SELECT i2 … Continue reading How to Fetch Oracle DBMS_OUTPUT from JDBC
How I Incorrectly Fetched JDBC ResultSets. Again.
You know JDBC, right? It's that really easy, concise API that we love to use to work with virtually any database, relational or not. It has essentially three types that you need to care about: ConnectionStatement (and its subtypes)ResultSet All the other types some sort of utilities. Now, with the above three, we can do … Continue reading How I Incorrectly Fetched JDBC ResultSets. Again.
jOOQ Tuesdays: Brett Wooldridge Shows What it Takes to Write the Fastest Java Connection Pool
Welcome to the jOOQ Tuesdays series. In this series, we’ll publish an article on the third Tuesday every other month where we interview someone we find exciting in our industry from a jOOQ perspective. This includes people who work with SQL, Java, Open Source, and a variety of other related topics. I'm very excited to … Continue reading jOOQ Tuesdays: Brett Wooldridge Shows What it Takes to Write the Fastest Java Connection Pool
How to Fetch Oracle 12c Implicit Cursors with JDBC and jOOQ
Earlier this week, I've blogged about how to execute SQL batches with JDBC and jOOQ. This was useful for the MySQL, SQL Server, and Sybase users among you. Today, we'll discuss a slightly more difficult task, how to fetch Oracle 12c implicit cursors - which are essentially the same thing. What's an implicit cursor? Oracle … Continue reading How to Fetch Oracle 12c Implicit Cursors with JDBC and jOOQ
How to Execute SQL Batches With JDBC and jOOQ
Some databases (in particular MySQL and T-SQL databases like SQL Server and Sybase) support a very nice feature: They allow for running a "batch" of statements in a single statement. For instance, in SQL Server, you can do something like this: -- Statement #1 DECLARE @table AS TABLE (id INT); -- Statement #2 SELECT * … Continue reading How to Execute SQL Batches With JDBC and jOOQ
How to Prevent JDBC Resource Leaks with JDBC and with jOOQ
In a recent consulting gig, I was analysing a client's connection pool issue in a productive system, where during some peak loads, all the Java processes involving database interactions just started queueing up until nothing really worked anymore. No exceptions, though, and when the peak load was gone in the evening, everything returned back to … Continue reading How to Prevent JDBC Resource Leaks with JDBC and with jOOQ