Why the Unjustified Cursor Hate?

Unraveling the Irrational Aversion to Cursors: The Cursor Dilemma

While it is understandable to choose more efficient set operations over cursors in relational database operations, the extreme aversion to cursors deserves further exploration. This irrational hatred, which often leads to excessive measures to avoid using cursors, raises many questions.

Expense Dilemma

The "overhead" associated with cursors is simply inherent to the Relational Database Management System (RDBMS) API. Cursors are the basis for the operation of various RDBMS internal components. However, using collection-based operators (which bundle cursor results into a single collection) can reduce API back-and-forth interactions.

Limitations of collections

Cursors predate languages ​​with first-class collection support. Lacking such collections, legacy languages ​​process one line at a time. Modern languages ​​overcome this limitation and provide seamless processing of result sets as collections.

Slowing down syndrome

Misuse of cursors, especially in nested loops, can exacerbate performance problems. A misunderstanding of relational joins can lead to the use of inefficient nested loops instead of simple joins, resulting in unacceptably slow operations. However, it is not the cursor itself that causes performance problems, but its improper use.

Scale Barrier

For massive result sets (such as those encountered during table dumps), cursors are still essential because set-based operations have difficulty materializing such large data sets in memory.

Alternative methods

An object-relational mapping (ORM) layer provides a viable solution that protects developers from the complexities of cursor management and decouples SQL from application code. This approach reduces the coding burden associated with cursors without sacrificing performance.

Conclusion

Cursors themselves are not evil and should not replace relational operations, but there is an irrational aversion to cursors that often leads to unnecessary avoidance. Understanding the role of cursors in an RDBMS architecture and the limitations of set-based operations can help eliminate this fear, allowing developers to use cursors effectively when necessary.

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