From d8f3752133d53cf4fe0d8040fc08dd033c02a222 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 31 Dec 1999 05:38:25 +0000
Subject: [PATCH] Generate double-sided LIKE indexquals that work even in weird
locales, by continuing to increment the rightmost character until we get a
string that is demonstrably greater than the pattern prefix.
---
src/backend/optimizer/path/indxpath.c | 208 ++++++++++++++++++++------
1 file changed, 163 insertions(+), 45 deletions(-)
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 1e9154edb95..b8aea22d107 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.74 1999/12/31 03:41:03 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.75 1999/12/31 05:38:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -23,6 +23,7 @@
#include "catalog/pg_amop.h"
#include "catalog/pg_operator.h"
#include "executor/executor.h"
+#include "mb/pg_wchar.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
@@ -92,7 +93,12 @@ static Prefix_Status regex_fixed_prefix(char *patt, bool case_insensitive,
char **prefix);
static List *prefix_quals(Var *leftop, Oid expr_op,
char *prefix, Prefix_Status pstatus);
+static char *make_greater_string(const char * str, 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);
+static bool string_lessthan(const char * str1, const char * str2,
+ Oid datatype);
/*
@@ -1653,7 +1659,7 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
case OID_TEXT_REGEXEQ_OP:
case OID_TEXT_ICREGEXEQ_OP:
if (! op_class(find_operator(">=", TEXTOID), opclass, relam) ||
- ! op_class(find_operator("<=", TEXTOID), opclass, relam))
+ ! op_class(find_operator("<", TEXTOID), opclass, relam))
isIndexable = false;
break;
@@ -1661,7 +1667,7 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
case OID_BPCHAR_REGEXEQ_OP:
case OID_BPCHAR_ICREGEXEQ_OP:
if (! op_class(find_operator(">=", BPCHAROID), opclass, relam) ||
- ! op_class(find_operator("<=", BPCHAROID), opclass, relam))
+ ! op_class(find_operator("<", BPCHAROID), opclass, relam))
isIndexable = false;
break;
@@ -1669,7 +1675,7 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
case OID_VARCHAR_REGEXEQ_OP:
case OID_VARCHAR_ICREGEXEQ_OP:
if (! op_class(find_operator(">=", VARCHAROID), opclass, relam) ||
- ! op_class(find_operator("<=", VARCHAROID), opclass, relam))
+ ! op_class(find_operator("<", VARCHAROID), opclass, relam))
isIndexable = false;
break;
@@ -1677,7 +1683,7 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
case OID_NAME_REGEXEQ_OP:
case OID_NAME_ICREGEXEQ_OP:
if (! op_class(find_operator(">=", NAMEOID), opclass, relam) ||
- ! op_class(find_operator("<=", NAMEOID), opclass, relam))
+ ! op_class(find_operator("<", NAMEOID), opclass, relam))
isIndexable = false;
break;
}
@@ -1774,7 +1780,7 @@ expand_indexqual_conditions(List *indexquals)
/*
* Extract the fixed prefix, if any, for a LIKE pattern.
- * *prefix is set to a palloc'd prefix string with 1 spare byte,
+ * *prefix is set to a palloc'd prefix string,
* or to NULL if no fixed prefix exists for the pattern.
* The return value distinguishes no fixed prefix, a partial prefix,
* or an exact-match-only pattern.
@@ -1786,7 +1792,7 @@ like_fixed_prefix(char *patt, char **prefix)
int pos,
match_pos;
- *prefix = match = palloc(strlen(patt)+2);
+ *prefix = match = palloc(strlen(patt)+1);
match_pos = 0;
for (pos = 0; patt[pos]; pos++)
@@ -1823,7 +1829,7 @@ like_fixed_prefix(char *patt, char **prefix)
/*
* Extract the fixed prefix, if any, for a regex pattern.
- * *prefix is set to a palloc'd prefix string with 1 spare byte,
+ * *prefix is set to a palloc'd prefix string,
* or to NULL if no fixed prefix exists for the pattern.
* The return value distinguishes no fixed prefix, a partial prefix,
* or an exact-match-only pattern.
@@ -1858,7 +1864,7 @@ regex_fixed_prefix(char *patt, bool case_insensitive,
}
/* OK, allocate space for pattern */
- *prefix = match = palloc(strlen(patt)+2);
+ *prefix = match = palloc(strlen(patt)+1);
match_pos = 0;
/* note start at pos 1 to skip leading ^ */
@@ -1906,11 +1912,10 @@ prefix_quals(Var *leftop, Oid expr_op,
List *result;
Oid datatype;
Oid oproid;
- void *conval;
Const *con;
Oper *op;
Expr *expr;
- int prefixlen;
+ char *greaterstr;
Assert(pstatus != Prefix_None);
@@ -1953,14 +1958,7 @@ prefix_quals(Var *leftop, Oid expr_op,
oproid = find_operator("=", datatype);
if (oproid == InvalidOid)
elog(ERROR, "prefix_quals: no = operator for type %u", datatype);
- /* Note: we cheat a little by assuming that textin() will do for
- * bpchar and varchar constants too...
- */
- conval = (datatype == NAMEOID) ?
- (void*) namein(prefix) : (void*) textin(prefix);
- con = makeConst(datatype, ((datatype == NAMEOID) ? NAMEDATALEN : -1),
- PointerGetDatum(conval),
- false, false, false, false);
+ con = string_to_const(prefix, datatype);
op = makeOper(oproid, InvalidOid, BOOLOID, 0, NULL);
expr = make_opclause(op, leftop, (Var *) con);
result = lcons(expr, NIL);
@@ -1975,43 +1973,92 @@ prefix_quals(Var *leftop, Oid expr_op,
oproid = find_operator(">=", datatype);
if (oproid == InvalidOid)
elog(ERROR, "prefix_quals: no >= operator for type %u", datatype);
- conval = (datatype == NAMEOID) ?
- (void*) namein(prefix) : (void*) textin(prefix);
- con = makeConst(datatype, ((datatype == NAMEOID) ? NAMEDATALEN : -1),
- PointerGetDatum(conval),
- false, false, false, false);
+ con = string_to_const(prefix, datatype);
op = makeOper(oproid, InvalidOid, BOOLOID, 0, NULL);
expr = make_opclause(op, leftop, (Var *) con);
result = lcons(expr, NIL);
/*
- * In ASCII locale we say "x <= prefix\377". This does not
- * work for non-ASCII collation orders, and it's not really
- * right even for ASCII. FIX ME!
- * Note we assume the passed prefix string is workspace with
- * an extra byte, as created by the xxx_fixed_prefix routines above.
+ * If we can create a string larger than the prefix, say "x < greaterstr".
*/
-#ifndef USE_LOCALE
- prefixlen = strlen(prefix);
- prefix[prefixlen] = '\377';
- prefix[prefixlen+1] = '\0';
+ greaterstr = make_greater_string(prefix, datatype);
+ if (greaterstr)
+ {
+ oproid = find_operator("<", datatype);
+ if (oproid == InvalidOid)
+ elog(ERROR, "prefix_quals: no < operator for type %u", datatype);
+ con = string_to_const(greaterstr, datatype);
+ op = makeOper(oproid, InvalidOid, BOOLOID, 0, NULL);
+ expr = make_opclause(op, leftop, (Var *) con);
+ result = lappend(result, expr);
+ pfree(greaterstr);
+ }
- oproid = find_operator("<=", datatype);
- if (oproid == InvalidOid)
- elog(ERROR, "prefix_quals: no <= operator for type %u", datatype);
- conval = (datatype == NAMEOID) ?
- (void*) namein(prefix) : (void*) textin(prefix);
- con = makeConst(datatype, ((datatype == NAMEOID) ? NAMEDATALEN : -1),
- PointerGetDatum(conval),
- false, false, false, false);
- op = makeOper(oproid, InvalidOid, BOOLOID, 0, NULL);
- expr = make_opclause(op, leftop, (Var *) con);
- result = lappend(result, expr);
+ return result;
+}
+
+/*
+ * 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 in a sufficiently weird locale, this might produce incorrect results?
+ * For example, in German I believe "ss" is treated specially --- if we are
+ * given "foos" and return "foot", will this actually be greater than "fooss"?
+ */
+static char *
+make_greater_string(const char * str, Oid datatype)
+{
+ char *workstr;
+ int len;
+
+ /* Make a modifiable copy, which will be our return value if successful */
+ workstr = pstrdup((char *) str);
+
+ while ((len = strlen(workstr)) > 0)
+ {
+ unsigned char *lastchar = (unsigned char *) (workstr + len - 1);
+
+ /*
+ * Try to generate a larger string by incrementing the last byte.
+ */
+ while (*lastchar < (unsigned char) 255)
+ {
+ (*lastchar)++;
+ if (string_lessthan(str, workstr, datatype))
+ return workstr; /* Success! */
+ }
+ /*
+ * Truncate off the last character, which might be more than 1 byte
+ * in MULTIBYTE case.
+ */
+#ifdef MULTIBYTE
+ len = pg_mbcliplen((const unsigned char *) workstr, len, len-1);
+ workstr[len] = '\0';
+#else
+ *lastchar = '\0';
#endif
+ }
- return result;
+ /* Failed... */
+ pfree(workstr);
+ return NULL;
}
+/*
+ * Handy subroutines for match_special_index_operator() and friends.
+ */
+
/* See if there is a binary op of the given name for the given datatype */
static Oid
find_operator(const char * opname, Oid datatype)
@@ -2027,3 +2074,74 @@ find_operator(const char * opname, Oid datatype)
return InvalidOid;
return optup->t_data->t_oid;
}
+
+/*
+ * Generate a Datum of the appropriate type from a C string.
+ * Note that all of the supported types are pass-by-ref, so the
+ * returned value should be pfree'd if no longer needed.
+ */
+static Datum
+string_to_datum(const char * str, Oid datatype)
+{
+ /* We cheat a little by assuming that textin() will do for
+ * bpchar and varchar constants too...
+ */
+ if (datatype == NAMEOID)
+ return PointerGetDatum(namein((char *) str));
+ else
+ return PointerGetDatum(textin((char *) str));
+}
+
+/*
+ * Generate a Const node of the appropriate type from a C string.
+ */
+static Const *
+string_to_const(const char * str, Oid datatype)
+{
+ Datum conval = string_to_datum(str, datatype);
+
+ return makeConst(datatype, ((datatype == NAMEOID) ? NAMEDATALEN : -1),
+ conval, false, false, false, false);
+}
+
+/*
+ * 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 = text_lt((text *) datum1, (text *) datum2);
+ break;
+
+ case BPCHAROID:
+ result = bpcharlt((char *) datum1, (char *) datum2);
+ break;
+
+ case VARCHAROID:
+ result = varcharlt((char *) datum1, (char *) datum2);
+ break;
+
+ case NAMEOID:
+ result = namelt((NameData *) datum1, (NameData *) datum2);
+ break;
+
+ default:
+ elog(ERROR, "string_lessthan: unexpected datatype %u", datatype);
+ result = false;
+ break;
+ }
+
+ pfree(DatumGetPointer(datum1));
+ pfree(DatumGetPointer(datum2));
+
+ return result;
+}
--
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