Introduce unicode_version(), icu_unicode_version(), and
unicode_assigned().
The latter requires introducing a new lookup table for the Unicode
General Category, which is generated along with the other Unicode
lookup tables.
Discussion: https://postgr.es/m/CA+TgmoYzYR-yhU6k1XFCADeyj=Oyz2PkVsa3iKv+keM8wp-F_A@mail.gmail.com
Reviewed-by: Peter Eisentraut
PostgreSQL 13 and newer versions are directly impacted by that through
the SQL function normalize(), which would cause a call of this function
to write one byte past its allocation if using in input an empty
string after recomposing the string with NFC and NFKC. Older versions
(v10~v12) are not directly affected by this problem as the only code
path using normalization is SASLprep in SCRAM authentication that
forbids the case of an empty string, but let's make the code more robust
anyway there so as any out-of-core callers of this function are covered.
The solution chosen to fix this issue is simple, with the addition of a
fast-exit path if the decomposed string is found as empty. This would
only happen for an empty string as at its lowest level a codepoint would
be decomposed as itself if it has no entry in the decomposition table or
if it has a decomposition size of 0.
Some tests are added to cover this issue in v13~. Note that an empty
string has always been considered as normalized (grammar "IS NF[K]{C,D}
NORMALIZED", through the SQL function is_normalized()) for all the
operations allowed (NFC, NFD, NFKC and NFKD) since this feature has been
introduced as of 2991ac5. This behavior is unchanged but some tests are
added in v13~ to check after that.
I have also checked "make normalization-check" in src/common/unicode/,
while on it (works in 13~, and breaks in older stable branches
independently of this commit).
The release notes should just mention this commit for v13~.
Reported-by: Matthijs van der Vleuten
Discussion: https://postgr.es/m/17277-0c527a373794e802@postgresql.org
Backpatch-through: 10
This adds SQL expressions NORMALIZE() and IS NORMALIZED to convert and
check Unicode normal forms, per SQL standard.
To support fast IS NORMALIZED tests, we pull in a new data file
DerivedNormalizationProps.txt from Unicode and build a lookup table
from that, using techniques similar to ones already used for other
Unicode data. make update-unicode will keep it up to date. We only
build and use these tables for the NFC and NFKC forms, because they
are too big for NFD and NFKD and the improvement is not significant
enough there.
Reviewed-by: Daniel Verite <daniel@manitou-mail.org>
Reviewed-by: Andreas Karlsson <andreas@proxel.se>
Discussion: https://www.postgresql.org/message-id/flat/c1909f27-c269-2ed9-12f8-3ab72c8caf7a@2ndquadrant.com
Jeff Davis
Michael Paquier
Peter Eisentraut