Re: [v9.2] make_greater_string() does not return a string in some cases

Hello, the work is finished.
Version 4 of the patch is attached to this message.
- Add rough description of the algorithm as comment to  pg_utf8_increment() and pg_eucjp_increment().
- Fixed a bug of pg_utf8_increment() found while  working. pg_(utf8|eucjp)_increment are retested on whole valid  code
pointsto be properly handled.
 
- The comment previously pointed out as being wrong in grammar  is left untouched. I'm sorry to bother you with my poor
English.
 


At Tue, 11 Oct 2011 16:55:00 +0900 (JST), Kyotaro HORIGUCHI <horiguchi.kyotaro@oss.ntt.co.jp> wrote 
> >   One thing I still think it would be useful to add,
> > though, is some comments to pg_utf8_increment() and
> > pg_eucjp_increment() describing the algorithm being used.  Can you
> > take a crack at that?
> 
>  Yes I'll do it in a day or two.
Regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 8ceea82..59f8c37 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -5664,6 +5664,19 @@ pattern_selectivity(Const *patt, Pattern_Type ptype)/*
+ * This function is "character increment" function for bytea used in
+ * make_greater_string() that has same interface with pg_wchar_tbl.charinc.
+ */
+static bool
+byte_increment(unsigned char *ptr, int len)
+{
+    if (*ptr >= 255) return false;
+
+    (*ptr)++;
+    return true;
+}
+
+/* * Try to generate a string greater than the given string or any * string it is a prefix of.  If successful, return
apalloc'd string * in the form of a Const node; else return NULL.
 
@@ -5702,6 +5715,7 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)    int
len;   Datum        cmpstr;    text       *cmptxt = NULL;
 
+    character_incrementer charincfunc;    /*     * Get a modifiable copy of the prefix string in C-string format, and
set
@@ -5763,29 +5777,33 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)        }    }
+    if (datatype == BYTEAOID)
+        charincfunc = &byte_increment;
+    else
+        charincfunc = pg_database_encoding_character_incrementer();
+    while (len > 0)    {
-        unsigned char *lastchar = (unsigned char *) (workstr + len - 1);
-        unsigned char savelastchar = *lastchar;
+        int charlen = 1;
+        unsigned char *lastchar;
+        Const       *workstr_const;
+        
+        if (datatype != BYTEAOID)
+            charlen = len - pg_mbcliplen(workstr, len, len - 1);
+        
+        lastchar = (unsigned char *) (workstr + len - charlen);        /*
-         * Try to generate a larger string by incrementing the last byte.
+         * Try to generate a larger string by incrementing the last byte or
+         * character.         */
-        while (*lastchar < (unsigned char) 255)
-        {
-            Const       *workstr_const;
-
-            (*lastchar)++;
-            if (datatype != BYTEAOID)
-            {
-                /* do not generate invalid encoding sequences */
-                if (!pg_verifymbstr(workstr, len, true))
-                    continue;
-                workstr_const = string_to_const(workstr, datatype);
-            }
-            else
+        if (charincfunc(lastchar, charlen))
+        {
+            if (datatype == BYTEAOID)                workstr_const = string_to_bytea_const(workstr, len);
+            else
+                workstr_const = string_to_const(workstr, datatype);            if
(DatumGetBool(FunctionCall2Coll(ltproc,                                              collation,
 
@@ -5804,20 +5822,10 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
pfree(workstr_const);       }
 
-        /* restore last byte so we don't confuse pg_mbcliplen */
-        *lastchar = savelastchar;
-        /*
-         * Truncate off the last character, which might be more than 1 byte,
-         * depending on the character encoding.
+         * Truncate off the last character or byte.         */
-        if (datatype != BYTEAOID && pg_database_encoding_max_length() > 1)
-            len = pg_mbcliplen(workstr, len, len - 1);
-        else
-            len -= 1;
-
-        if (datatype != BYTEAOID)
-            workstr[len] = '\0';
+        len -= charlen;    }    /* Failed... */
diff --git a/src/backend/utils/mb/wchar.c b/src/backend/utils/mb/wchar.c
index f23732f..a213636 100644
--- a/src/backend/utils/mb/wchar.c
+++ b/src/backend/utils/mb/wchar.c
@@ -1336,6 +1336,264 @@ pg_utf8_islegal(const unsigned char *source, int length)/*
*-------------------------------------------------------------------
+ * character incrementer
+ *
+ * These functions accept "charptr", a pointer to the first byte of a
+ * maybe-multibyte character. Try `increment' the character and return
+ * true if successed.  If these functions returns false, the character
+ * should be untouched.  These functions must be implemented in
+ * correspondence with verifiers, in other words, the rewrited
+ * character by this function must pass the check by pg_*_verifier()
+ * if returns true.
+ * -------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+static bool
+pg_generic_charinc(unsigned char *charptr, int len)
+{
+     unsigned char *lastchar = (unsigned char *) (charptr + len - 1);
+     unsigned char savelastchar = *lastchar;
+     const char *const_charptr = (const char *)charptr;
+ 
+     while (*lastchar < (unsigned char) 255)
+     {
+         (*lastchar)++;
+         if (!pg_verifymbstr(const_charptr, len, true))
+             continue;
+         return true;
+     }
+ 
+     *lastchar = savelastchar;
+     return false;
+}
+ 
+/*
+ * Calculate the valid UTF-8 byte sequence that is the smallest of the
+ * greater than the given valid UTF-8 byte sequence for single
+ * character. The word `valid' here means that pg_utf8_islegal() says
+ * that it is valid.  pg_utf8_increment does this roughly with the
+ * following algorithm.
+ * 
+ *  - If the length of the sequence is 1, the byte is between 0x01 and
+ *    0x7f. It is simplly incremented if less than 0x7f.
+ *
+ *  - Otherwise the bytes after the first one ranges between 0x80 and
+ *    0xbf.  The sequence is incremented from the last byte and the
+ *    carry is propagated up to the first byte.
+ *
+ * Only the UTF-8 byte sequences corresponding to the following
+ * unicode point which have no character allocated make this function
+ * to fail in spite of its validity.
+ *
+ * U+0007F, U+007FF, U+0FFFF, U+10FFFF
+ * 
+ */
+static bool
+pg_utf8_increment(unsigned char *charptr, int length)
+{
+     unsigned char a;
+     unsigned char bak[4];
+    unsigned char limit;
+ 
+     switch (length)
+     {
+         default:
+             /* reject lengths 5 and 6 for now */
+             return false;
+         case 4:
+            bak[3] = charptr[3];
+             a = charptr[3];
+             if (a < 0xBF)
+             {
+                 charptr[3]++;
+                 break;
+             }
+             charptr[3] = 0x80;
+             /* FALL THRU */
+         case 3:
+            bak[2] = charptr[2];
+             a = charptr[2];
+             if (a < 0xBF)
+             {
+                 charptr[2]++;
+                 break;
+             }
+             charptr[2] = 0x80;
+             /* FALL THRU */
+         case 2:
+            bak[1] = charptr[1];
+             a = charptr[1];
+            switch (*charptr)
+            {
+            case 0xED:
+                limit = 0x9F;
+                break;
+
+            case 0xF4:
+                limit = 0x8F;
+                break;
+
+            default:
+                limit = 0xBF;
+
+            }
+
+            if (a < limit)
+            {
+                 charptr[1]++;
+                 break;
+             }
+
+             charptr[1] = 0x80;
+             /* FALL THRU */
+         case 1:
+            bak[0] = *charptr;
+             a = *charptr;
+             if (a == 0x7F || a == 0xDF || a == 0xEF || a == 0xF4)
+            {
+                /* Rewinding modified bytes and return fail. length is
+                 * confirmed to be between 1 and 4 here. */
+                memcpy(charptr, bak, length);
+                 return false;
+             }
+             charptr[0]++;
+             break;
+     }
+     
+     return true;
+}
+ 
+/* Calculate the valid EUC-JP byte sequence that is the smallest of
+ * the greater than the given valid EUC-JP byte sequence for single
+ * character. The word `valid' here means that pg_eucjp_verifier()
+ * syas that it is valid. This function does this roughly with the
+ * following algorithm.
+ *
+ *  - If the sequence starts with SS2(0x8e), it must be a two-byte
+ *    sequence representing JIS X 0201 characters with the second byte
+ *    ranges between 0xa1 and 0xde. It is simplly incremented at the
+ *    second byte if less than 0xde, and otherwise rewrite whole the
+ *    sequence to 0xa1 0xa1 as the result.
+ *
+ *  - If the sequence starts with SS3(0x8f), it must be a three-byte
+ *    sequence which the last two bytes ranges between 0xa1 and 0xfe.
+ *    The bytes are incremented from the last within the range and
+ *    propagate the carry up to the first byte.
+ *
+ *  - If the sequence starts with the values other than the aboves and
+ *    its MSB is set, it must be a two-byte sequence representing JIS
+ *    X 0208 characters with both bytes ranges between 0xa1 and 0xfe.
+ *    The bytes are incremented from the latter within the range and
+ *    propagate the carry up to the first byte.
+ *
+ *  - Otherwise the sequence is consists of single byte representing
+ *    ASCII characters. It is incremented up to 0x7f.
+ *    
+ * Only three EUC-JP byte sequences shown below which has no character
+ * allocated make this function to fail in spite of its validity.
+ *
+ * 0x7f, 0xfe 0xfe, 0x8f 0xfe 0xfe
+ *
+ */
+static bool
+pg_eucjp_increment(unsigned char *charptr, int length)
+{
+     unsigned char bak[3];
+     unsigned char c1, c2;
+     signed int i;
+ 
+     c1 = *charptr;
+ 
+     switch (c1)
+     {
+         case SS2:    /* JIS X 0201 */
+             if (length != 2) return false;
+ 
+             c2 = charptr[1];
+ 
+             if (c2 > 0xde)
+                 charptr[0] = charptr[1] = 0xa1;
+             else if (c2 < 0xa1)
+                 charptr[1] = 0xa1;
+             else
+                 charptr[1]++;
+ 
+             break;
+ 
+         case SS3:    /* JIS X 0212 */
+             if (length != 3) return false;
+ 
+             for (i = 2 ; i > 0 ; i--)
+             {
+                bak[i] = charptr[i];
+                 c2 = charptr[i];
+                 if (c2 < 0xa1)
+                 {
+                     charptr[i] = 0xa1;
+                     return true;
+                 }
+                 else if (c2 < 0xfe)
+                 {
+                     charptr[i]++;
+                     break;
+                 }
+                 charptr[i] = 0xa1;
+             }
+ 
+ 
+             if (i == 0)      /* Out of 3-byte code region */
+             {
+                charptr[1] = bak[1];
+                charptr[2] = bak[2];
+                 return false;
+             }
+             
+             break;
+ 
+         default:
+             if (IS_HIGHBIT_SET(c1))     /* JIS X 0208? */
+             {
+                 if (length != 2) return false;
+           
+                 for (i = 1 ; i >= 0 ; i--)    /* i must be signed */
+                 {
+                    bak[i] = charptr[i];
+                     c2 = charptr[i];
+                     if (c2 < 0xa1)
+                     {
+                         charptr[i] = 0xa1;
+                         return true;
+                     }
+                     else if (c2 < 0xfe)
+                     {
+                         charptr[i]++;
+                         break;
+                     }
+                     charptr[i] = 0xa1;
+                 }
+           
+                 if (i < 0)    /*  Out of 2 byte code region */
+                 {
+                     charptr[0] = bak[0];
+                     charptr[1] = bak[1];
+                     return false;
+                 }
+             }
+             else
+             {    /* ASCII, single byte */
+                 if (c1 > 0x7e)
+                     return false;
+                 (*charptr)++;
+             }
+     }
+   
+     return true;
+}
+#endif
+
+/*
+ *------------------------------------------------------------------- * encoding info table * XXX must be sorted by
thesame order as enum pg_enc (in mb/pg_wchar.h) *-------------------------------------------------------------------
 
@@ -1459,6 +1717,25 @@ pg_database_encoding_max_length(void)}/*
+ * give the character incrementer for the encoding for the current database
+ */
+character_incrementer
+pg_database_encoding_character_incrementer(void)
+{
+    switch (GetDatabaseEncoding())
+    {
+        case PG_UTF8:
+            return pg_utf8_increment;
+            
+        case PG_EUC_JP:
+            return pg_eucjp_increment;
+            
+        default:
+            return pg_generic_charinc;
+    }
+}
+
+/* * Verify mbstr to make sure that it is validly encoded in the current * database encoding.  Otherwise same as
pg_verify_mbstr().*/
 
diff --git a/src/include/mb/pg_wchar.h b/src/include/mb/pg_wchar.h
index 826c7af..728175c 100644
--- a/src/include/mb/pg_wchar.h
+++ b/src/include/mb/pg_wchar.h
@@ -284,6 +284,8 @@ typedef int (*mblen_converter) (const unsigned char *mbstr);typedef int (*mbdisplaylen_converter)
(constunsigned char *mbstr);
 
+typedef bool (*character_incrementer) (unsigned char *mbstr, int len);
+typedef int (*mbverifier) (const unsigned char *mbstr, int len);typedef struct
@@ -389,6 +391,7 @@ extern int pg_encoding_mbcliplen(int encoding, const char *mbstr,extern int
pg_mbcharcliplen(constchar *mbstr, int len, int imit);extern int    pg_encoding_max_length(int encoding);extern int
pg_database_encoding_max_length(void);
+extern character_incrementer pg_database_encoding_character_incrementer(void);extern int    PrepareClientEncoding(int
encoding);externint    SetClientEncoding(int encoding);