E'' is more a marker than a type. I realize making E a type might work, but it seems unusual. What we could do is backpatch E'' to 8.0.X as a no-op like it will be in 8.1. --------------------------------------------------------------------------- Jeff Davis wrote: > >From what I've read, it looks like 8.1 will introduce the E'' escape > string, and eventually postgresql will change the normal '' strings to > be more SQL-compliant. > > If I wanted to start being forwards-compatible right now, and I have > existing databases in 7.4 and 8.0, my idea was to create a type E. Any > string using that type would work in 7.4/8.0 as normal, and then when I > upgrade to 8.1 I will drop the type and the applications will still work. > > To do that is relatively simple, I'd just use the textin/out functions > that already exist to create the type (which in 7.4/8.0 will give the > desired behavior of escaping). Like so: > > CREATE FUNCTION ein(CSTRING) RETURNS E AS 'textin' LANGUAGE internal; > > CREATE FUNCTION eout(E) RETURNS CSTRING AS 'textout' LANGUAGE internal; > > CREATE TYPE E (input=ein,output=eout); > > CREATE CAST (E AS TEXT) WITHOUT FUNCTION AS IMPLICIT; > > CREATE CAST (TEXT AS E) WITHOUT FUNCTION AS IMPLICIT; > > Then, when I upgrade a system to 8.1, I can just remove the type, and > all the applications will still work. Eventually when the '' strings are > changed, I can start using those again, but in a SQL-compliant way. > > Does this migration path make sense? Will creating the type possibly > cause casting problems of some kind? I read something about possibly > "backpatching" the E'' string to 8.0. If someone did that, what would be > the difference between applying a backpatch and what I did above? > > One thing that has me concerned about the idea is that there are some > string constants, like B'' and X'' that aren't really types. Does that > mean that E'' won't be a type? Why are B'' and X'' not types, and are > there any other notations like that that are not types? > > Regards, > Jeff Davis > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > -- Bruce Momjian | http://candle.pha.pa.us pgman@xxxxxxxxxxxxxxxx | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
