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Displaying posts with tag: stored functions (reset)
Why MySQL Stored Procedures, Functions and Triggers Are Bad For Performance

MySQL stored procedures, functions and triggers are tempting constructs for application developers. However, as I discovered, there can be an impact on database performance when using MySQL stored routines. Not being entirely sure of what I was seeing during a customer visit, I set out to create some simple tests to measure the impact of triggers on database performance. The outcome might surprise you.

Why stored routines are not optimal performance wise: short version

Recently, I worked with a customer to profile the performance of triggers and stored routines. What I’ve learned about stored routines: “dead” code (the code in a branch which will never run) can still significantly slow down the response time of a function/procedure/trigger. We will need to be careful to clean up what we do not need.

Profiling MySQL stored functions

Let’s compare these four simple stored functions (in MySQL 5.7): …

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Implicit Commit Functions?

Somebody asked about the possibility of putting DML statements inside MySQL stored functions. DML statements like the INSERT, UPDATE, and DELETE. When I said, “Yes, you can put DML statements inside functions.” They showed me the error they encountered, which is only raised at compilation when you put an explicit COMMIT statement or a Data Definition Language (DDL) statement (CREATE, ALTER, DROP, or RENAME) inside a MySQL function. The actual error message displayed is:

ERROR 1422 (HY000): Explicit OR implicit commit IS NOT allowed IN stored FUNCTION OR TRIGGER.

While an explicit COMMIT is obvious when placed inside a function, the implicit COMMIT statement isn’t obvious unless you know a DDL statement generates one. This means you can’t include any DDL statement inside a stored …

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Next Week’s MySQL Sessions at ODTUG Kaleidoscope

By now you know that there is a MySQL Track during next week’s ODTUG Kaleidoscope in Washington, DC. Ronald Bradford and I organized the schedule at the last minute (Ronald did a lot of the work!). It was difficult to fill a schedule with 19 sessions that are either 1 hour or 1.5 hours long, and to do it I ended up with three presentations.

At each presentation I will be giving away a copy of The MySQL Administrator’s Bible, so be sure to show up! All MySQL track sessions are in Maryland C, and all times are Eastern.

On Monday, June 28th from 4 pm – 5:30 pm I will be presenting …

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A micro-benchmark of stored routines in MySQL

Ever wondered how fast stored routines are in MySQL? I just ran a quick micro-benchmark to compare the speed of a stored function against a "roughly equivalent" subquery. The idea -- and there may be shortcomings that are poisoning the results here, your comments welcome -- is to see how fast the SQL procedure code is at doing basically the same thing the subquery code does natively (so to speak).

Before we go further, I want to make sure you know that the queries I'm writing here are deliberately mis-optimized to force a bad execution plan. You should never use IN() subqueries the way I do, at least not in MySQL 5.1 and earlier.

I loaded the World sample database and cooked up this query:

PLAIN TEXT SQL:

  1. SELECT sql_no_cache sum(ci.Population) FROM City AS ci
  2.   WHERE …
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Showing entries 1 to 4