On Tue, Sep 6, 2016 at 10:40 AM, Doug Doole <ddo...@salesforce.com> wrote: >> The ICU ABI (not API) is also versioned. The way that this is done is >> that all functions are actually macros to a versioned symbol. So >> ucol_open() is actually a macro that expands to, say, ucol_open_57() in >> ICU version 57. (They also got rid of a dot in their versions a while >> ago.) It's basically hand-crafted symbol versioning. That way, you can >> link with multiple versions of ICU at the same time. However, the >> purpose of that, as I understand it, is so that plugins can have a >> different version of ICU loaded than the main process or another plugin. > > In terms of postgres using the right version of ICU, it doesn't buy >> anything beyond what the soname mechanism does. > > You can access the versioned API as well, it's just not documented. (The ICU > team does support this - we worked very closely with them when doing all > this.) We exploited the versioned API when we learned that there is no > guarantee of backwards compatibility in collations. You can't just change a > collation under a user (at least that was our opinion) since it can cause > all sorts of problems. Refreshing a collation (especially on the fly) is a > lot more work than we were prepared to take on. So we exploited the > versioned APIs.
I originally got some of this information from the ICU Doxygen site for the C API, which isn't great documentation, but also isn't bad. I admit that there are certainly gaps in my understanding of how to bridge our requirements with versioning to what ICU can give us. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers