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Indexing support for pattern matching operations via separate operator

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class when lc_collate is not C.
This commit is contained in:
Peter Eisentraut
2003-05-15 15:50:21 +00:00
parent 2a2f6cfa39
commit 2c0556068f
20 changed files with 489 additions and 208 deletions
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123
src/backend/utils/adt/selfuncs.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.136 2003/04/16 04:37:58 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.137 2003/05/15 15:50:18 petere Exp $
*
*-------------------------------------------------------------------------
*/
@ -180,8 +180,6 @@ static void get_join_vars(List *args, Var **var1, Var **var2);
static Selectivity prefix_selectivity(Query *root, Var *var, Oid vartype,
Const *prefix);
static Selectivity pattern_selectivity(Const *patt, Pattern_Type ptype);
static bool string_lessthan(const char *str1, const char *str2,
Oid datatype);
static Oid find_operator(const char *opname, Oid datatype);
static Datum string_to_datum(const char *str, Oid datatype);
static Const *string_to_const(const char *str, Oid datatype);
@ -3619,51 +3617,21 @@ pattern_selectivity(Const *patt, Pattern_Type ptype)
/*
* We want to test whether the database's LC_COLLATE setting is safe for
* LIKE/regexp index optimization.
* Try to generate a string greater than the given string or any
* string it is a prefix of. If successful, return a palloc'd string;
* else return NULL.
*
* The key requirement here is that given a prefix string, say "foo",
* we must be able to generate another string "fop" that is greater
* than all strings "foobar" starting with "foo". Unfortunately, a
* non-C locale may have arbitrary collation rules in which "fop" >
* "foo" is not sufficient to ensure "fop" > "foobar". Until we can
* come up with a more bulletproof way of generating the upper-bound
* string, the optimization is disabled in all non-C locales.
* than all strings "foobar" starting with "foo".
*
* (In theory, locales other than C may be LIKE-safe so this function
* could be different from lc_collate_is_c(), but in a different
* theory, non-C locales are completely unpredictable so it's unlikely
* to happen.)
* If we max out the righthand byte, truncate off the last character
* and start incrementing the next. For example, if "z" were the last
* character in the sort order, then we could produce "foo" as a
* string greater than "fonz".
*
* Be sure to maintain the correspondence with the code in initdb.
*/
bool
locale_is_like_safe(void)
{
return lc_collate_is_c();
}
/*
* Try to generate a string greater than the given string or any string it is
* a prefix of. If successful, return a palloc'd string; else return NULL.
*
* To work correctly in non-ASCII locales with weird collation orders,
* we cannot simply increment "foo" to "fop" --- we have to check whether
* we actually produced a string greater than the given one. If not,
* increment the righthand byte again and repeat. If we max out the righthand
* byte, truncate off the last character and start incrementing the next.
* For example, if "z" were the last character in the sort order, then we
* could produce "foo" as a string greater than "fonz".
*
* This could be rather slow in the worst case, but in most cases we won't
* have to try more than one or two strings before succeeding.
*
* XXX this is actually not sufficient, since it only copes with the case
* where individual characters collate in an order different from their
* numeric code assignments. It does not handle cases where there are
* cross-character effects, such as specially sorted digraphs, multiple
* sort passes, etc. For now, we just shut down the whole thing in locales
* that do such things :-(
* This could be rather slow in the worst case, but in most cases we
* won't have to try more than one or two strings before succeeding.
*/
Const *
make_greater_string(const Const *str_const)
@ -3699,18 +3667,16 @@ make_greater_string(const Const *str_const)
/*
* Try to generate a larger string by incrementing the last byte.
*/
while (*lastchar < (unsigned char) 255)
if (*lastchar < (unsigned char) 255)
{
(*lastchar)++;
if (string_lessthan(str, workstr, datatype))
{
/* Success! */
Const *workstr_const = string_to_const(workstr, datatype);
Const *workstr_const;
pfree(str);
pfree(workstr);
return workstr_const;
}
(*lastchar)++;
workstr_const = string_to_const(workstr, datatype);
pfree(str);
pfree(workstr);
return workstr_const;
}
/* restore last byte so we don't confuse pg_mbcliplen */
@ -3736,57 +3702,6 @@ make_greater_string(const Const *str_const)
return (Const *) NULL;
}
/*
* Test whether two strings are "<" according to the rules of the given
* datatype. We do this the hard way, ie, actually calling the type's
* "<" operator function, to ensure we get the right result...
*/
static bool
string_lessthan(const char *str1, const char *str2, Oid datatype)
{
Datum datum1 = string_to_datum(str1, datatype);
Datum datum2 = string_to_datum(str2, datatype);
bool result;
switch (datatype)
{
case TEXTOID:
result = DatumGetBool(DirectFunctionCall2(text_lt,
datum1, datum2));
break;
case BPCHAROID:
result = DatumGetBool(DirectFunctionCall2(bpcharlt,
datum1, datum2));
break;
case VARCHAROID:
result = DatumGetBool(DirectFunctionCall2(varcharlt,
datum1, datum2));
break;
case NAMEOID:
result = DatumGetBool(DirectFunctionCall2(namelt,
datum1, datum2));
break;
case BYTEAOID:
result = DatumGetBool(DirectFunctionCall2(bytealt,
datum1, datum2));
break;
default:
elog(ERROR, "string_lessthan: unexpected datatype %u", datatype);
result = false;
break;
}
pfree(DatumGetPointer(datum1));
pfree(DatumGetPointer(datum2));
return result;
}
/* See if there is a binary op of the given name for the given datatype */
/* NB: we assume that only built-in system operators are searched for */
static Oid