Michael Fuhr <[EMAIL PROTECTED]> writes: > On Mon, Aug 15, 2005 at 08:21:23PM -0400, Tom Lane wrote: >> Given that we consider trailing spaces in char(n) to be semantically >> insignificant, would it make sense to strip them before doing the >> regex pattern match?
> How standards-compliant would that be? Does the standard specify > what should happen when using SIMILAR TO with a char(n) value? Hmm ... suddenly I'm getting a strong sense of deja vu ... think we've been around this merry-go-round before. SQL99 says ii) The <predicate> MC LIKE PC is true if there exists a partitioning of MCV into substrings such that: 1) A substring of MCV is a sequence of 0 (zero) or more contiguous <character representation>s of MCV and each <character representation> of MCV is part of exactly one substring. 2) If the i-th substring specifier of PCV is an arbitrary character specifier, the i-th substring of MCV is any single <character representation>. 3) If the i-th substring specifier of PCV is an arbitrary string specifier, then the i-th substring of MCV is any sequence of 0 (zero) or more <character representation>s. 4) If the i-th substring specifier of PCV is neither an arbitrary character specifier nor an arbitrary string specifier, then the i-th substring of MCV is equal to that substring specifier according to the collating sequence of the <like predicate>, without the appending of <space> characters to MCV, and has the same length as that substring specifier. 5) The number of substrings of MCV is equal to the number of substring specifiers of PCV. Rule ii.4 says that you use the collating sequence associated with the data values, which is where the SQL spec keeps its space sensitivity information --- but the restrictions about not adding space characters and having the same length seem to be intended to prevent use of pad-space-insensitivity to create a match. I think we read this text before, came to the same conclusion, and put in the special operator to make it behave that way. So ... never mind. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq