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Collations with nondeterministic comparison

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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
This commit is contained in:
Peter Eisentraut
2019-03-22 12:09:32 +01:00
parent 2ab6d28d23
commit 5e1963fb76
69 changed files with 2090 additions and 242 deletions
Download Patch File Download Diff File Expand all files Collapse all files

100
src/backend/access/hash/hashfunc.c
View File

@@ -27,8 +27,10 @@
#include "postgres.h"
#include "access/hash.h"
#include "catalog/pg_collation.h"
#include "utils/builtins.h"
#include "utils/hashutils.h"
#include "utils/pg_locale.h"
/*
* Datatype-specific hash functions.
@@ -243,15 +245,51 @@ Datum
hashtext(PG_FUNCTION_ARGS)
{
text *key = PG_GETARG_TEXT_PP(0);
Oid collid = PG_GET_COLLATION();
pg_locale_t mylocale = 0;
Datum result;
/*
* Note: this is currently identical in behavior to hashvarlena, but keep
* it as a separate function in case we someday want to do something
* different in non-C locales. (See also hashbpchar, if so.)
*/
result = hash_any((unsigned char *) VARDATA_ANY(key),
VARSIZE_ANY_EXHDR(key));
if (!collid)
ereport(ERROR,
(errcode(ERRCODE_INDETERMINATE_COLLATION),
errmsg("could not determine which collation to use for string hashing"),
errhint("Use the COLLATE clause to set the collation explicitly.")));
if (!lc_collate_is_c(collid) && collid != DEFAULT_COLLATION_OID)
mylocale = pg_newlocale_from_collation(collid);
if (!mylocale || mylocale->deterministic)
{
result = hash_any((unsigned char *) VARDATA_ANY(key),
VARSIZE_ANY_EXHDR(key));
}
else
{
#ifdef USE_ICU
if (mylocale->provider == COLLPROVIDER_ICU)
{
int32_t ulen = -1;
UChar *uchar = NULL;
Size bsize;
uint8_t *buf;
ulen = icu_to_uchar(&uchar, VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));
bsize = ucol_getSortKey(mylocale->info.icu.ucol,
uchar, ulen, NULL, 0);
buf = palloc(bsize);
ucol_getSortKey(mylocale->info.icu.ucol,
uchar, ulen, buf, bsize);
result = hash_any(buf, bsize);
pfree(buf);
}
else
#endif
/* shouldn't happen */
elog(ERROR, "unsupported collprovider: %c", mylocale->provider);
}
/* Avoid leaking memory for toasted inputs */
PG_FREE_IF_COPY(key, 0);
@@ -263,12 +301,52 @@ Datum
hashtextextended(PG_FUNCTION_ARGS)
{
text *key = PG_GETARG_TEXT_PP(0);
Oid collid = PG_GET_COLLATION();
pg_locale_t mylocale = 0;
Datum result;
/* Same approach as hashtext */
result = hash_any_extended((unsigned char *) VARDATA_ANY(key),
VARSIZE_ANY_EXHDR(key),
PG_GETARG_INT64(1));
if (!collid)
ereport(ERROR,
(errcode(ERRCODE_INDETERMINATE_COLLATION),
errmsg("could not determine which collation to use for string hashing"),
errhint("Use the COLLATE clause to set the collation explicitly.")));
if (!lc_collate_is_c(collid) && collid != DEFAULT_COLLATION_OID)
mylocale = pg_newlocale_from_collation(collid);
if (!mylocale || mylocale->deterministic)
{
result = hash_any_extended((unsigned char *) VARDATA_ANY(key),
VARSIZE_ANY_EXHDR(key),
PG_GETARG_INT64(1));
}
else
{
#ifdef USE_ICU
if (mylocale->provider == COLLPROVIDER_ICU)
{
int32_t ulen = -1;
UChar *uchar = NULL;
Size bsize;
uint8_t *buf;
ulen = icu_to_uchar(&uchar, VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));
bsize = ucol_getSortKey(mylocale->info.icu.ucol,
uchar, ulen, NULL, 0);
buf = palloc(bsize);
ucol_getSortKey(mylocale->info.icu.ucol,
uchar, ulen, buf, bsize);
result = hash_any_extended(buf, bsize, PG_GETARG_INT64(1));
pfree(buf);
}
else
#endif
/* shouldn't happen */
elog(ERROR, "unsupported collprovider: %c", mylocale->provider);
}
PG_FREE_IF_COPY(key, 0);