Infinite loop getting stored procedure name from DDL

Question

I have this regular expression to check if a DLL have a prodcedure

var expReg = "(((ALTER|CREATE|OR|REPLACE| )*)+)?PROCEDURE.*";    
return (Regex.IsMatch(textProcedure, expReg, RegexOptions.IgnoreCase)

I use it with SQL Server or Oracle DLL.

Sometimes works, and sometime have a infinite loop.

What is the problem? Any help is greatly appreciated.

What do you want to match? Please, give some sample strings and expected result. — Toto, Dec 12 '14 at 14:44
possible duplicate of [Why my Python regular expression pattern run so slowly?](http://stackoverflow.com/questions/27448200/why-my-python-regular-expression-pattern-run-so-slowly) — ivan_pozdeev, Dec 12 '14 at 17:17

score 2 · Accepted Answer · answered Dec 12 '14 at 14:41

A pattern of the form (X*)+ is a very bad idea in regex, because it can cause catastrophic backtracking. This kind of pattern forces the regex engine to try all the possible combinations before failing. This can take a long time.

In your case, I think the * is not required, simply use:

(?:ALTER|CREATE|OR|REPLACE|\s)+PROCEDURE

I've removed the ? too because otherwise the mere presence of the word PROCEDURE would be sufficient for the pattern to match.

This can be further simplified to:

(?:ALTER|CREATE|REPLACE)\s+PROCEDURE

Since it should be sufficient to match REPLACE PROCEDURE in the string CREATE OR REPLACE PROCEDURE.

Thanks Lucas. You send a solution, and a cause of my poor regular expresion. I think that your solution can help some people. — Victor Sanchez, Dec 15 '14 at 14:14

Infinite loop getting stored procedure name from DDL

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