On 2019-Dec-03, Alvaro Herrera wrote: > Now, I have to say that this doesn't make me terribly happy, because I > would like the additional ability to limit the printed values to N > bytes. This means the new function would have to have an additional > argument to indicate the maximum length (pass 0 to print all args > whole) ... and the logic then because more involved because we need > logic to stop printing early.
So after actually writing this, it seems that it's better to have a separate path for this; otherwise you need to scan the whole input string (strchr or friends), which might be long. I tried to see how to make strnlen() work for us, but I found no simple way to print the "..." at the end. So this just runs once per char. I think that's okay, since the intended usage is to print a few dozen bytes, like ExecBuildSlotValueDescription does (64 bytes is what all its callers do). Another point: this implementation is not strict about how many input characters it prints. It counts up to maxlen *output* characters, which means if it duplicates a ', that's one less input char printed. (Given the usage of this function, this seems a feature rather than a bug. The first implementation did the opposite, and on the whole it seemed worse.) If anyone can suggest a smarter implementation, I'm all ears. (Maybe do strnlen(maxlen), then count strnlen(1) starting at that point -- so if that returns >=1, print the "..."?) -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
