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Office Hours June 2020: Exploring the PL/SQL Profilers

The PL/SQL engine offers two profiler utilities to help identify performance bottlenecks in your application:

1. DBMS_PROFILER

That's the name of the package that provides an API to the profiler that computes the time that your PL/SQL program spends at each line, in each subprogram. Saves runtime statistics in database tables, which you can then query.

2. DBMS_HPROF

The hierarchical profiler; this utility reports the dynamic execution program profile of your PL/SQL program, organized by subprogram invocations. It accounts for SQL and PL/SQL execution times separately. Requiring no special source or compile-time preparation, it generates reports in HTML. You can also store profiler data and results in relational format in database tables for custom report generation (such as third-party tools offer).

You can find lots more information about these two profilers in the documentation.

In our June 2nd 2020 Office Hours session, I am very pleased to have Shashank Barki, an experienced d…
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Virtual Private Database: Beyond the Basics

Virtual Private Database (VPD), also referred to as row-level security or RLS, is a feature built into the Oracle Database that allows you to set up security policies on tables that restrict which rows a user can see or change based on the policy logic.

One of the nicest things about VPD is that this logic (and the fact that a filter is being applied) is completely invisible to the user. They just see the data relevant to them and none the wiser about all that other data in the data.

Here's a simple example to drive the point home: suppose I am building a health care application and it contains a patients table. The security policy is straightforward:
A patient can only see their own information.A doctor can see only the information about their own patients.A clinic administrator can see information only about the patients in their clinic. In all three cases, the user would sign on to the application and execute this identical query and only their rows would appear.

SELECT * FROM p…

Why DBMS_OUTPUT.PUT_LINE should not be in your application code

A database developer recently came across my Bulletproof PL/SQL presentation, which includes this slide.

That first item in the list caught his attention:
Never put calls to DBMS_OUTPUT.PUT_LINE in your application code. So he sent me an email asking why I would say that. Well, I suppose that is the problem with publishing slide decks. All the explanatory verbiage is missing. I suppose maybe I should do a video. :-)

But in the meantime, allow me to explain.

First, what does DBMS_OUTPUT.PUT_LINE do? It writes text out to a buffer, and when your current PL/SQL block terminates, the buffer is displayed on your screen.

[Note: there can be more to it than that. For example, you could in your own code call DBMS_OUTPUT.GET_LINE(S) to get the contents of the buffer and do something with it, but I will keep things simple right now.]

Second, if I am telling you not to use this built-in, how could text from your program be displayed on your screen?

Not without a lot of difficulty, that's fo…

An Application Alerting Utility

A few weeks ago, Mike Hichwa asked me to come up with a package that would implement a simple alerting utility: specify a triggering event (based on a query or a PL/SQL expression) and then take the specified actions when it is triggered.

Seeing as he is my boss, I said "OK" and got to work (my favorite kind of work: writing some PL/SQL code). We did our usual bit to expand scope, then did our usual bit to agree that this is enough for a first pass. And then Mike said: "Go ahead and write a blog post about it, share it with the community."

So here goes.

The basic idea is we start up a job using DBMS_SCHEDULER that runs every N minutes. When it runs, it checks to see if any alerts need to be triggered. If so, it then takes one or more actions associated with that alert.

Let's start with our tables.
Utility configuration How often should the job wake up? Should it disable checking for alerts? What is the name of the "callout" for sending emails? And if…

Results are in for the PL/SQL Challenge Championship for 2019!

Another Oracle Dev Gym championship completed! Find below the rankings for the PL/SQL Challenge Championship for 2019. The number next to the player's name is the number of times that player has participated in a championship. Below the table of results for this championship, you will find another list showing the championship history of each of these players.

Congratulations first and foremost to our top-ranked players:

1st Place: MarkusId

2nd Place: mentzel.iudith

3rd Place: NielsHecker


Next, congratulations to everyone who played in the championship. We hope you found it entertaining, challenging and educational. And for those who were not able to participate in the championship, we will make the championship as a whole available as a workout, so you can take it just like these players did.

Finally, our deepest gratitude to our reviewer, Elic, who has once again performed an invaluable service to our community.

RankNameTotal Time% CorrectTotal Score1MarkusId (1)28 m83%41852ment…

Rankings for Logic Annual Championship for 2019

You will find below the rankings for the Logic Annual Championship for 2019, held in February 2020 on the Oracle Dev Gym. The number next to the player's name is the number of times that player has participated in a championship. Below the table of results for this championship, you will find another list showing the championship history of each of these players.

Congratulations first and foremost to our top-ranked players:

1st Place: Stelios Vlasopoulos

2nd Place: Sartograph

3rd Place: NielsHecker


Next, congratulations to everyone who played in the championship. We hope you found it entertaining, challenging and educational. And for those who were not able to participate in the championship, you can take the quizzes through the Practice feature. We will also make the championship as a whole available as a Workout, so you can take it just like these players did.

Finally, many thanks to Eli Feuerstein, Logic Quizmaster who provided a very challenging set of quizzes, and our deepest…

PL/SQL Office Hours: Virtual Private Database in the Wild

Virtual Private Database (VPD), also referred to as row-level security or RLS, is a feature built into the Oracle Database that allows you to set up security policies on tables that restrict which rows a user can see or change based on the policy logic.

One of the nicest things about VPD is that this logic (and the fact that a filter is being applied) is completely invisible to the user. They just see the data relevant to them and none the wiser about all that other data in the data.

Here's a simple example to drive the point home: suppose I am building a health care application and it contains a patients table. The security policy is straightforward:

A patient can only see their own information.
A doctor can see only the information about their own patients.
A clinic administrator can see information only about the patients in their clinic.

In all three cases, the user would sign on to the application and execute the same query:

SELECT * FROM patients

and only their rows would ap…