Bruce Momjian wrote: > I have committed the first draft of the PG 17 release notes; you can > see the results here: > > https://momjian.us/pgsql_docs/release-17.html
About the changes in collations: <quote> Create a "builtin" collation provider similar to libc's C locale (Jeff Davis) It uses a "C" locale which is identical but independent of libc, but it allows the use of non-"C" collations like "en_US" and "C.UTF-8" with the "C" locale, which libc does not. MORE? </quote> The new builtin provider has two collations: * ucs_basic which is 100% identical to "C". It was introduced several versions ago and the v17 novelty is simply to change its pg_collation.collprovider from 'c' to 'b'. * pg_c_utf8 which sorts like "C" but is Unicode-aware for the rest, which makes it quite different from "C". It's also different from the other UTF-8 collations that could be used up to v17 in that it does not depend on an external library, making it free from the collation OS-upgrade risks. The part that is concretely of interest to users is the introduction of pg_c_utf8. As described in [1]: <quote> pg_c_utf8 This collation sorts by Unicode code point values rather than natural language order. For the functions lower, initcap, and upper, it uses Unicode simple case mapping. For pattern matching (including regular expressions), it uses the POSIX Compatible variant of Unicode Compatibility Properties. Behavior is efficient and stable within a Postgres major version. This collation is only available for encoding UTF8. </quote> I'd suggest that the relnote entry should be more like a condensed version of that description, without mentioning en_US or C.UTF-8, whose existence and semantics are OS-dependent, contrary to pg_c_utf8. [1] https://www.postgresql.org/docs/devel/collation.html Best regards, -- Daniel Vérité https://postgresql.verite.pro/ Twitter: @DanielVerite
