ahhhh. This is what confused me-- the documentation for the prepare statement mentions this perf boost being quite explicit about including the null, then also makes the ambiguous statement that "the zSQL string ends at either the first '\000' or '\u0000' character or the nbyteth byte, whichever comes first." Since the null gets ignored, I interpreted this as meaning that the nth byte was ignored, and that providing the proper data size was the source of the performance boost (possibly by eliminating a search for null termination).
Thank you for the clarification :-). -sean -----Original Message----- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Richard Hipp Sent: Wednesday, September 21, 2011 12:23 PM To: General Discussion of SQLite Database Subject: Re: [sqlite] c-api document suggestion On Wed, Sep 21, 2011 at 3:05 PM, Sean Pieper <spie...@nvidia.com> wrote: > There's an apparent inconsistency in the behavior of sqlite3_bind_text and > sqlite3_prepare_v2. > If the user supplies the length of the argument rather than using -1, > bind_text expects that this length exclude the null termination, whereas > prepare apparently expects it to include the null termination. > No, sqlite3_prepare_v2() does not *expect* N to be size+1. sqlite3_prepare_v2() with length N will process all text up to the first zero-character, or the first N bytes, whichever come first. So you are perfectly free to set N equal to the length of the string exclusive of the zero-terminator, just as in bind_text(). However, if you are willing to make N equal to the length of the string plus one, then SQLite can avoid a memcpy() and thus give a very small performance advantage. But that is purely an optimization, and a minor one at that. It will work correctly regardless of whether N is strlen() or strlen()+1. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users ----------------------------------------------------------------------------------- This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. ----------------------------------------------------------------------------------- _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
