9.7. Pattern Matching

9.7. Pattern Matching

9.7. 模式匹配

There are three separate approaches to pattern matching provided by PostgreSQL: the traditional SQL LIKE operator, the more recent SIMILAR TO operator (added in SQL:1999), and POSIX-style regular expressions. Aside from the basic “does this string match this pattern?” operators, functions are available to extract or replace matching substrings and to split a string at matching locations.

PostgreSQL提供了三種單獨的模式匹配方法：傳統的SQL LIKE運算符，SIMILAR TO運算符（在SQL：1999中添加）和POSIX樣式的正則表達式。除了基本的“此字符串是否匹配此模式？”運算符，函數可用於提取或替換匹配的子字符串並在匹配的位置拆分字符串。

 

Tip

小貼士

If you have pattern matching needs that go beyond this, consider writing a user-defined function in Perl or Tcl.

如果有超出此範圍的模式匹配需求，可以考慮使用Perl或Tcl編寫用戶自定義的函數。

 

Caution

注意

While most regular-expression searches can be executed very quickly, regular expressions can be contrived that take arbitrary amounts of time and memory to process. Be wary of accepting regular-expression search patterns from hostile sources. If you must do so, it is advisable to impose a statement timeout.

儘管大多數正則表達式搜索可以非常快速地執行，但卻也可以構造能夠耗費任意時間及內存去執行的正則表達式。 因此從未知來源接受正則表達式的時候，一定要謹慎。 如果必須這樣做，則建議強制限制語句超時。

 

Searches using SIMILAR TO patterns have the same security hazards, since SIMILAR TO provides many of the same capabilities as POSIX-style regular expressions.

使用SIMILAR TO模式進行的搜索具有相同的安全隱患，因爲SIMILAR TO提供了許多與POSIX樣式正則表達式相同的功能。

 

LIKE searches, being much simpler than the other two options, are safer to use with possibly-hostile pattern sources.

與其他兩個選項相比，LIKE搜索要簡單得多，它與可能有害的模式源一起使用安全性會高一些。