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| author | Peter Eisentraut <peter@eisentraut.org> | 2019-03-22 12:09:32 +0100 |
|---|---|---|
| committer | Peter Eisentraut <peter@eisentraut.org> | 2019-03-22 12:12:43 +0100 |
| commit | 5e1963fb764e9cc092e0f7b58b28985c311431d9 (patch) | |
| tree | 544492f24e3d48d00bd2a19c11663f84f1e18ce4 /src/backend/utils/adt/like_support.c | |
| parent | 2ab6d28d233af17987ea323e3235b2bda89b4f2e (diff) | |
| download | postgresql-5e1963fb764e9cc092e0f7b58b28985c311431d9.tar.gz postgresql-5e1963fb764e9cc092e0f7b58b28985c311431d9.zip | |
Collations with nondeterministic comparison
This adds a flag "deterministic" to collations. If that is false,
such a collation disables various optimizations that assume that
strings are equal only if they are byte-wise equal. That then allows
use cases such as case-insensitive or accent-insensitive comparisons
or handling of strings with different Unicode normal forms.
This functionality is only supported with the ICU provider. At least
glibc doesn't appear to have any locales that work in a
nondeterministic way, so it's not worth supporting this for the libc
provider.
The term "deterministic comparison" in this context is from Unicode
Technical Standard #10
(https://unicode.org/reports/tr10/#Deterministic_Comparison).
This patch makes changes in three areas:
- CREATE COLLATION DDL changes and system catalog changes to support
this new flag.
- Many executor nodes and auxiliary code are extended to track
collations. Previously, this code would just throw away collation
information, because the eventually-called user-defined functions
didn't use it since they only cared about equality, which didn't
need collation information.
- String data type functions that do equality comparisons and hashing
are changed to take the (non-)deterministic flag into account. For
comparison, this just means skipping various shortcuts and tie
breakers that use byte-wise comparison. For hashing, we first need
to convert the input string to a canonical "sort key" using the ICU
analogue of strxfrm().
Reviewed-by: Daniel Verite <daniel@manitou-mail.org>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://www.postgresql.org/message-id/flat/1ccc668f-4cbc-0bef-af67-450b47cdfee7@2ndquadrant.com
Diffstat (limited to 'src/backend/utils/adt/like_support.c')
| -rw-r--r-- | src/backend/utils/adt/like_support.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/src/backend/utils/adt/like_support.c b/src/backend/utils/adt/like_support.c index 69509811ef7..a65e63736c4 100644 --- a/src/backend/utils/adt/like_support.c +++ b/src/backend/utils/adt/like_support.c @@ -258,6 +258,20 @@ match_pattern_prefix(Node *leftop, patt = (Const *) rightop; /* + * Not supported if the expression collation is nondeterministic. The + * optimized equality or prefix tests use bytewise comparisons, which is + * not consistent with nondeterministic collations. The actual + * pattern-matching implementation functions will later error out that + * pattern-matching is not supported with nondeterministic collations. + * (We could also error out here, but by doing it later we get more + * precise error messages.) (It should be possible to support at least + * Pattern_Prefix_Exact, but no point as along as the actual + * pattern-matching implementations don't support it.) + */ + if (!get_collation_isdeterministic(expr_coll)) + return NIL; + + /* * Try to extract a fixed prefix from the pattern. */ pstatus = pattern_fixed_prefix(patt, ptype, expr_coll, |