DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports Events Over 2 million developers have joined DZone. Join Today! Thanks for visiting DZone today,
Edit Profile Manage Email Subscriptions Moderation Admin Console How to Post to DZone Article Submission Guidelines
View Profile
Sign Out
Refcards
Trend Reports
Events
Zones
Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Partner Zones AWS Cloud
by AWS Developer Relations
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Partner Zones
AWS Cloud
by AWS Developer Relations
Building Scalable Real-Time Apps with AstraDB and Vaadin
Register Now

Trending

  • How To Integrate Microsoft Team With Cypress Cloud
  • Tomorrow’s Cloud Today: Unpacking the Future of Cloud Computing
  • Replacing Apache Hive, Elasticsearch, and PostgreSQL With Apache Doris
  • Design Patterns for Microservices: Ambassador, Anti-Corruption Layer, and Backends for Frontends

Trending

  • How To Integrate Microsoft Team With Cypress Cloud
  • Tomorrow’s Cloud Today: Unpacking the Future of Cloud Computing
  • Replacing Apache Hive, Elasticsearch, and PostgreSQL With Apache Doris
  • Design Patterns for Microservices: Ambassador, Anti-Corruption Layer, and Backends for Frontends
  1. DZone
  2. Data Engineering
  3. Databases
  4. PL/SQL Puzzle: What Assumptions Am I Making?

PL/SQL Puzzle: What Assumptions Am I Making?

In this article, see what assumptions the author is making in his code.

Steven Feuerstein user avatar by
Steven Feuerstein
·
Jan. 02, 20 · Opinion
Like (7)
Save
Tweet
Share
13.96K Views

Join the DZone community and get the full member experience.

Join For Free

Person doing puzzle

Almost certainly, whenever you write a procedure or function, you make certain assumptions. Some of them are quite reasonable, such as "I assume my database is up and running." Some of them are scary, such as, "I assume my users will never change their minds."

But many simply go unnoticed. You don't even realize you are making an assumption until it smacks you in face, most likely in production, when an unexpected error exposes the assumption.

So in this PL/SQL puzzle, as I state on Twitter:

The procedure shown below compiles without error. What assumptions am I making so that when it executes, it does not terminate with an exception?

OK, let's dive in. I provide below all of the assumptions I was aware of and also some others that were provided on Twitter on the very active discussion that followed. As usual, I learned something new from the community!

You might also like:  Code You Should Never See in PL/SQL

Line 3: By hardcoding the datatype to VARCHAR2(100), we assume that the last names in the employees table never exceed that length. Better to use: TABLE OF employees.last_name%TYPE

Lines 7 - 10: An unlimited BULK COLLECT assumes there will always be enough PGA (session memory) for the collection, no matter how big the table gets. A nasty assumption, bound to fail long after you left the project. Use FETCH with LIMIT instead as demonstrated in this LiveSQL script.

Also, Jacek Gebal suggests another related assumption:  The number of rows in the collection doesn't exceed the limit for nested tables. Since that limit is 2**31 (2 raised to the 31st power), I am pretty sure you will run out of PGA memory first. But he's right: it's still an assumption. :-)

Line 12: Assumes that there is at least 1 element in the collection. Otherwise, FIRST and LAST return NULL and PL/SQL raises

 ORA-06502: PL/SQL: numeric or value error 

What should you do instead? Much better:

 FOR indx IN 1 .. l_employees.COUNT 

Which assumes a sequentially filled collection from 1. So, what is better about that? BULK COLLECT always fills a collection from index 1 and sequentially from there.

Line 14: Assumes that do_more_stuff accepts VARCHAR2 or CLOB values and also does not raise exception.

Line 16:  There is no exception handler! So one really big fat assumption I make is that none of the code in the procedure will cause an exception to be raised. In particular, as pointed out by Abul Samed, I assume that Exception handling is done in procedure do_more_stuff.

Or...I have decided that I do not care if an exception is raised in either of the procedures, because my standards dictate that I only handle exceptions at the outermost block and this procedure is called by others. I don't generally consider that a good idea. I like to handle exceptions locally, log any application state specific to the block (such as values of local variables).

What else did I assume?

Did I miss anything? Do you have any stories to share about assumptions you've made in your code or seen in other developers' code that resulted in some less-than-optimal results?

Further Reading

A Guide to High-Performance PL/SQL

PL/SQL — Don’t Mix and Match Scope

PL/SQL Database

Published at DZone with permission of Steven Feuerstein, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Trending

  • How To Integrate Microsoft Team With Cypress Cloud
  • Tomorrow’s Cloud Today: Unpacking the Future of Cloud Computing
  • Replacing Apache Hive, Elasticsearch, and PostgreSQL With Apache Doris
  • Design Patterns for Microservices: Ambassador, Anti-Corruption Layer, and Backends for Frontends

Comments

Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 600 Park Offices Drive
  • Suite 300
  • Durham, NC 27709
  • support@dzone.com

Let's be friends: