MDEV-25449 Add MY_COLLATION_HANDLER::strnncollsp_nchars()bb-10.3-bar-MDEV-25449

22 files changed, 312 insertions, 33 deletions

diff --git a/include/m_ctype.h b/include/m_ctype.h
index 1cdff1f54cc..82243855dd1 100644
--- a/include/m_ctype.h
+++ b/include/m_ctype.h
@@ -330,6 +330,32 @@ struct my_collation_handler_st
 		       const uchar *, size_t, const uchar *, size_t, my_bool);
   int     (*strnncollsp)(CHARSET_INFO *,
                          const uchar *, size_t, const uchar *, size_t);
+  /*
+    strncollsp_nchars() - similar to strnncollsp() but compares not more
+                          than nchars characters only.
+    This function is usually used to compare CHAR(N) values stored in records.
+    These record values are padded with trailing spaces up to the maximum
+    possible octet length. For example, a column of the data type
+      `CHAR(3) CHARACTER SET utf8mb4`
+    reserves 12 octets. If we store ASCII 'abc', the record we'll contain
+    'abc' followed by 9 space characters. Trailing spaces are just fillers here,
+    they are not actual data! To compare such buffers with CHAR(3) values,
+    we cannot use strncollsp(a,12,b,12) - it may return a wrong result in case
+    of a NOPAD collation of a multi-byte character set.
+    In such scenarios we should use strnncollsp_nchars(a,12,b,12,3).
+
+    Note, this function counts contraction parts as individual characters.
+    For example, the Czech letter 'ch' (in Czech collations)
+    is ordinary counted by "nchars" as TWO characters (not as one).
+    Also, we presume that the "nchars" limit will ignore only
+    trailing filler space characters (not important data). So the limit
+    will never tear apart contractions like 'ch' in the way that
+    'c' takes part in comparison while 'h' is ignored.
+  */
+  int     (*strnncollsp_nchars)(CHARSET_INFO *,
+                                const uchar *str1, size_t len1,
+                                const uchar *str2, size_t len2,
+                                size_t nchars);
   size_t     (*strnxfrm)(CHARSET_INFO *,
                          uchar *dst, size_t dstlen, uint nweights,
                          const uchar *src, size_t srclen, uint flags);
diff --git a/sql/field.cc b/sql/field.cc
index 76d9a3ccf95..4bbbc740b39 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -7304,23 +7304,10 @@ Field_string::compatible_field_size(uint field_metadata,
 
 int Field_string::cmp(const uchar *a_ptr, const uchar *b_ptr)
 {
-  size_t a_len, b_len;
-
-  if (field_charset->mbmaxlen != 1)
-  {
-    size_t char_len= field_length/field_charset->mbmaxlen;
-    a_len= my_charpos(field_charset, a_ptr, a_ptr + field_length, char_len);
-    b_len= my_charpos(field_charset, b_ptr, b_ptr + field_length, char_len);
-  }
-  else
-    a_len= b_len= field_length;
-  /*
-    We have to remove end space to be able to compare multi-byte-characters
-    like in latin_de 'ae' and 0xe4
-  */
-  return field_charset->coll->strnncollsp(field_charset,
-                                          a_ptr, a_len,
-                                          b_ptr, b_len);
+  return field_charset->coll->strnncollsp_nchars(field_charset,
+                                                 a_ptr, field_length,
+                                                 b_ptr, field_length,
+                                                 Field_string::char_length());
 }
 
 
@@ -7718,19 +7705,6 @@ int Field_varstring::cmp(const uchar *a_ptr, const uchar *b_ptr)
 }
 
 
-static int cmp_str_prefix(const uchar *ua, size_t alen, const uchar *ub,
-                          size_t blen, size_t prefix, CHARSET_INFO *cs)
-{
-  const char *a= (char*)ua, *b= (char*)ub;
-  MY_STRCOPY_STATUS status;
-  prefix/= cs->mbmaxlen;
-  alen= cs->cset->well_formed_char_length(cs, a, a + alen, prefix, &status);
-  blen= cs->cset->well_formed_char_length(cs, b, b + blen, prefix, &status);
-  return cs->coll->strnncollsp(cs, ua, alen, ub, blen);
-}
-
-
-
 int Field_varstring::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
                                 size_t prefix_len)
 {
@@ -7750,8 +7724,12 @@ int Field_varstring::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
     a_length= uint2korr(a_ptr);
     b_length= uint2korr(b_ptr);
   }
-  return cmp_str_prefix(a_ptr+length_bytes, a_length, b_ptr+length_bytes,
-                        b_length, prefix_len, field_charset);
+  return field_charset->coll->strnncollsp_nchars(field_charset,
+                                                 a_ptr + length_bytes,
+                                                 a_length,
+                                                 b_ptr + length_bytes,
+                                                 b_length,
+                                                 prefix_len / field_charset->mbmaxlen);
 }
 
 
@@ -8535,7 +8513,10 @@ int Field_blob::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
   memcpy(&blob1, a_ptr+packlength, sizeof(char*));
   memcpy(&blob2, b_ptr+packlength, sizeof(char*));
   size_t a_len= get_length(a_ptr), b_len= get_length(b_ptr);
-  return cmp_str_prefix(blob1, a_len, blob2, b_len, prefix_len, field_charset);
+  return field_charset->coll->strnncollsp_nchars(field_charset,
+                                                 blob1, a_len,
+                                                 blob2, b_len,
+                                                 prefix_len / field_charset->mbmaxlen);
 }
 
 
diff --git a/strings/ctype-big5.c b/strings/ctype-big5.c
index 3991a219ab5..fdaa34eeaf0 100644
--- a/strings/ctype-big5.c
+++ b/strings/ctype-big5.c
@@ -6711,6 +6711,7 @@ static MY_COLLATION_HANDLER my_collation_handler_big5_chinese_ci=
   NULL,			/* init */
   my_strnncoll_big5_chinese_ci,
   my_strnncollsp_big5_chinese_ci,
+  my_strnncollsp_nchars_big5_chinese_ci,
   my_strnxfrm_big5_chinese_ci,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -6727,6 +6728,7 @@ static MY_COLLATION_HANDLER my_collation_handler_big5_bin=
   NULL,	                /* init */
   my_strnncoll_big5_bin,
   my_strnncollsp_big5_bin,
+  my_strnncollsp_nchars_big5_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -6743,6 +6745,7 @@ static MY_COLLATION_HANDLER my_collation_handler_big5_chinese_nopad_ci=
   NULL,			/* init */
   my_strnncoll_big5_chinese_ci,
   my_strnncollsp_big5_chinese_nopad_ci,
+  my_strnncollsp_nchars_big5_chinese_nopad_ci,
   my_strnxfrm_big5_chinese_nopad_ci,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -6759,6 +6762,7 @@ static MY_COLLATION_HANDLER my_collation_handler_big5_nopad_bin=
   NULL,	                /* init */
   my_strnncoll_big5_bin,
   my_strnncollsp_big5_nopad_bin,
+  my_strnncollsp_nchars_big5_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-bin.c b/strings/ctype-bin.c
index c052e427322..e70111da89b 100644
--- a/strings/ctype-bin.c
+++ b/strings/ctype-bin.c
@@ -125,6 +125,17 @@ static int my_strnncollsp_binary(CHARSET_INFO * cs __attribute__((unused)),
 }
 
 
+static int my_strnncollsp_nchars_binary(CHARSET_INFO * cs __attribute__((unused)),
+                                        const uchar *s, size_t slen,
+                                        const uchar *t, size_t tlen,
+                                        size_t nchars)
+{
+  set_if_smaller(slen, nchars);
+  set_if_smaller(tlen, nchars);
+  return my_strnncoll_binary(cs, s, slen, t, tlen, 0);
+}
+
+
 static int my_strnncoll_8bit_bin(CHARSET_INFO * cs __attribute__((unused)),
                                  const uchar *s, size_t slen,
                                  const uchar *t, size_t tlen,
@@ -199,6 +210,17 @@ static int my_strnncollsp_8bit_bin(CHARSET_INFO * cs __attribute__((unused)),
 }
 
 
+static int my_strnncollsp_nchars_8bit_bin(CHARSET_INFO * cs,
+                                          const uchar *a, size_t a_length,
+                                          const uchar *b, size_t b_length,
+                                          size_t nchars)
+{
+  set_if_smaller(a_length, nchars);
+  set_if_smaller(b_length, nchars);
+  return my_strnncollsp_8bit_bin(cs, a, a_length, b, b_length);
+}
+
+
 static int my_strnncollsp_8bit_nopad_bin(CHARSET_INFO * cs
                                          __attribute__((unused)),
                                          const uchar *a, size_t a_length,
@@ -208,6 +230,17 @@ static int my_strnncollsp_8bit_nopad_bin(CHARSET_INFO * cs
 }
 
 
+static int my_strnncollsp_nchars_8bit_nopad_bin(CHARSET_INFO * cs,
+                                         const uchar *a, size_t a_length,
+                                         const uchar *b, size_t b_length,
+                                         size_t nchars)
+{
+  set_if_smaller(a_length, nchars);
+  set_if_smaller(b_length, nchars);
+  return my_strnncollsp_8bit_nopad_bin(cs, a, a_length, b, b_length);
+}
+
+
 /* This function is used for all conversion functions */
 
 static size_t my_case_str_bin(CHARSET_INFO *cs __attribute__((unused)),
@@ -487,6 +520,7 @@ MY_COLLATION_HANDLER my_collation_8bit_bin_handler =
   my_coll_init_8bit_bin,
   my_strnncoll_8bit_bin,
   my_strnncollsp_8bit_bin,
+  my_strnncollsp_nchars_8bit_bin,
   my_strnxfrm_8bit_bin,
   my_strnxfrmlen_simple,
   my_like_range_simple,
@@ -503,6 +537,7 @@ MY_COLLATION_HANDLER my_collation_8bit_nopad_bin_handler =
   my_coll_init_8bit_bin,
   my_strnncoll_8bit_bin,
   my_strnncollsp_8bit_nopad_bin,
+  my_strnncollsp_nchars_8bit_nopad_bin,
   my_strnxfrm_8bit_nopad_bin,
   my_strnxfrmlen_simple,
   my_like_range_simple,
@@ -519,6 +554,7 @@ static MY_COLLATION_HANDLER my_collation_binary_handler =
   NULL,			/* init */
   my_strnncoll_binary,
   my_strnncollsp_binary,
+  my_strnncollsp_nchars_binary,
   my_strnxfrm_8bit_bin,
   my_strnxfrmlen_simple,
   my_like_range_simple,
diff --git a/strings/ctype-cp932.c b/strings/ctype-cp932.c
index bf97d1feb83..94450af4b91 100644
--- a/strings/ctype-cp932.c
+++ b/strings/ctype-cp932.c
@@ -34667,6 +34667,7 @@ static MY_COLLATION_HANDLER my_collation_handler_cp932_japanese_ci=
   NULL,                  /* init */
   my_strnncoll_cp932_japanese_ci,
   my_strnncollsp_cp932_japanese_ci,
+  my_strnncollsp_nchars_cp932_japanese_ci,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34683,6 +34684,7 @@ static MY_COLLATION_HANDLER my_collation_handler_cp932_bin=
   NULL,	                /* init */
   my_strnncoll_cp932_bin,
   my_strnncollsp_cp932_bin,
+  my_strnncollsp_nchars_cp932_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34699,6 +34701,7 @@ static MY_COLLATION_HANDLER my_collation_handler_cp932_japanese_nopad_ci=
   NULL,                  /* init */
   my_strnncoll_cp932_japanese_ci,
   my_strnncollsp_cp932_japanese_nopad_ci,
+  my_strnncollsp_nchars_cp932_japanese_nopad_ci,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34715,6 +34718,7 @@ static MY_COLLATION_HANDLER my_collation_handler_cp932_nopad_bin=
   NULL,	                /* init */
   my_strnncoll_cp932_bin,
   my_strnncollsp_cp932_nopad_bin,
+  my_strnncollsp_nchars_cp932_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-czech.c b/strings/ctype-czech.c
index 17c4c98c24e..33d43d4dd4e 100644
--- a/strings/ctype-czech.c
+++ b/strings/ctype-czech.c
@@ -610,6 +610,7 @@ static MY_COLLATION_HANDLER my_collation_latin2_czech_ci_handler =
   NULL,			/* init */
   my_strnncoll_czech,
   my_strnncollsp_czech,
+  my_strnncollsp_nchars_generic_8bit,
   my_strnxfrm_czech,
   my_strnxfrmlen_czech,
   my_like_range_czech,
diff --git a/strings/ctype-euc_kr.c b/strings/ctype-euc_kr.c
index deb13957900..22f8c4ec7c0 100644
--- a/strings/ctype-euc_kr.c
+++ b/strings/ctype-euc_kr.c
@@ -9957,6 +9957,7 @@ static MY_COLLATION_HANDLER my_collation_handler_euckr_korean_ci=
   NULL,                 /* init */
   my_strnncoll_euckr_korean_ci,
   my_strnncollsp_euckr_korean_ci,
+  my_strnncollsp_nchars_euckr_korean_ci,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -9973,6 +9974,7 @@ static MY_COLLATION_HANDLER my_collation_handler_euckr_bin=
   NULL,                 /* init */
   my_strnncoll_euckr_bin,
   my_strnncollsp_euckr_bin,
+  my_strnncollsp_nchars_euckr_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -9989,6 +9991,7 @@ static MY_COLLATION_HANDLER my_collation_handler_euckr_korean_nopad_ci=
   NULL,                 /* init */
   my_strnncoll_euckr_korean_ci,
   my_strnncollsp_euckr_korean_nopad_ci,
+  my_strnncollsp_nchars_euckr_korean_nopad_ci,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -10005,6 +10008,7 @@ static MY_COLLATION_HANDLER my_collation_handler_euckr_nopad_bin=
   NULL,                 /* init */
   my_strnncoll_euckr_bin,
   my_strnncollsp_euckr_nopad_bin,
+  my_strnncollsp_nchars_euckr_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-eucjpms.c b/strings/ctype-eucjpms.c
index 118e8286703..58ea37d36e6 100644
--- a/strings/ctype-eucjpms.c
+++ b/strings/ctype-eucjpms.c
@@ -67495,6 +67495,7 @@ static MY_COLLATION_HANDLER my_collation_eucjpms_japanese_ci_handler =
     NULL,		/* init */
     my_strnncoll_eucjpms_japanese_ci,
     my_strnncollsp_eucjpms_japanese_ci,
+    my_strnncollsp_nchars_eucjpms_japanese_ci,
     my_strnxfrm_mb,	/* strnxfrm     */
     my_strnxfrmlen_simple,
     my_like_range_mb,   /* like_range   */
@@ -67511,6 +67512,7 @@ static MY_COLLATION_HANDLER my_collation_eucjpms_bin_handler =
     NULL,		/* init */
     my_strnncoll_eucjpms_bin,
     my_strnncollsp_eucjpms_bin,
+    my_strnncollsp_nchars_eucjpms_bin,
     my_strnxfrm_mb,
     my_strnxfrmlen_simple,
     my_like_range_mb,
@@ -67527,6 +67529,7 @@ static MY_COLLATION_HANDLER my_collation_eucjpms_japanese_nopad_ci_handler =
     NULL,		/* init */
     my_strnncoll_eucjpms_japanese_ci,
     my_strnncollsp_eucjpms_japanese_nopad_ci,
+    my_strnncollsp_nchars_eucjpms_japanese_nopad_ci,
     my_strnxfrm_mb_nopad,	/* strnxfrm     */
     my_strnxfrmlen_simple,
     my_like_range_mb,   /* like_range   */
@@ -67543,6 +67546,7 @@ static MY_COLLATION_HANDLER my_collation_eucjpms_nopad_bin_handler =
     NULL,		/* init */
     my_strnncoll_eucjpms_bin,
     my_strnncollsp_eucjpms_nopad_bin,
+    my_strnncollsp_nchars_eucjpms_nopad_bin,
     my_strnxfrm_mb_nopad,
     my_strnxfrmlen_simple,
     my_like_range_mb,
diff --git a/strings/ctype-gb2312.c b/strings/ctype-gb2312.c
index 166619bf5cc..84246ad6671 100644
--- a/strings/ctype-gb2312.c
+++ b/strings/ctype-gb2312.c
@@ -6362,6 +6362,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gb2312_chinese_ci=
   NULL,                 /* init */
   my_strnncoll_gb2312_chinese_ci,
   my_strnncollsp_gb2312_chinese_ci,
+  my_strnncollsp_nchars_gb2312_chinese_ci,
   my_strnxfrm_mb,       /* strnxfrm   */
   my_strnxfrmlen_simple,
   my_like_range_mb,     /* like_range */
@@ -6378,6 +6379,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gb2312_bin=
   NULL,	                /* init */
   my_strnncoll_gb2312_bin,
   my_strnncollsp_gb2312_bin,
+  my_strnncollsp_nchars_gb2312_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -6394,6 +6396,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gb2312_chinese_nopad_ci=
   NULL,                 /* init */
   my_strnncoll_gb2312_chinese_ci,
   my_strnncollsp_gb2312_chinese_nopad_ci,
+  my_strnncollsp_nchars_gb2312_chinese_nopad_ci,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -6410,6 +6413,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gb2312_nopad_bin=
   NULL,	                /* init */
   my_strnncoll_gb2312_bin,
   my_strnncollsp_gb2312_nopad_bin,
+  my_strnncollsp_nchars_gb2312_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-gbk.c b/strings/ctype-gbk.c
index efaa2e5c728..d7ea47c409f 100644
--- a/strings/ctype-gbk.c
+++ b/strings/ctype-gbk.c
@@ -10645,6 +10645,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gbk_chinese_ci=
   NULL,                 /* init */
   my_strnncoll_gbk_chinese_ci,
   my_strnncollsp_gbk_chinese_ci,
+  my_strnncollsp_nchars_gbk_chinese_ci,
   my_strnxfrm_gbk_chinese_ci,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -10661,6 +10662,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gbk_bin=
   NULL,                 /* init */
   my_strnncoll_gbk_bin,
   my_strnncollsp_gbk_bin,
+  my_strnncollsp_nchars_gbk_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -10677,6 +10679,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gbk_chinese_nopad_ci=
   NULL,                 /* init */
   my_strnncoll_gbk_chinese_ci,
   my_strnncollsp_gbk_chinese_nopad_ci,
+  my_strnncollsp_nchars_gbk_chinese_nopad_ci,
   my_strnxfrm_gbk_chinese_nopad_ci,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -10693,6 +10696,7 @@ static MY_COLLATION_HANDLER my_collation_handler_gbk_nopad_bin=
   NULL,                 /* init */
   my_strnncoll_gbk_bin,
   my_strnncollsp_gbk_nopad_bin,
+  my_strnncollsp_nchars_gbk_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-latin1.c b/strings/ctype-latin1.c
index f9fa1488aa6..bcf1cc6c9f1 100644
--- a/strings/ctype-latin1.c
+++ b/strings/ctype-latin1.c
@@ -726,6 +726,7 @@ static MY_COLLATION_HANDLER my_collation_german2_ci_handler=
   NULL,			/* init */
   my_strnncoll_latin1_de,
   my_strnncollsp_latin1_de,
+  my_strnncollsp_nchars_generic_8bit,
   my_strnxfrm_latin1_de,
   my_strnxfrmlen_simple,
   my_like_range_simple,
diff --git a/strings/ctype-simple.c b/strings/ctype-simple.c
index 17cb51ff8cb..2227f595885 100644
--- a/strings/ctype-simple.c
+++ b/strings/ctype-simple.c
@@ -208,6 +208,18 @@ int my_strnncollsp_simple(CHARSET_INFO * cs, const uchar *a, size_t a_length,
 }
 
 
+static int
+my_strnncollsp_nchars_simple(CHARSET_INFO * cs,
+                             const uchar *a, size_t a_length,
+                             const uchar *b, size_t b_length,
+                             size_t nchars)
+{
+  set_if_smaller(a_length, nchars);
+  set_if_smaller(b_length, nchars);
+  return my_strnncollsp_simple(cs, a, a_length, b, b_length);
+}
+
+
 int my_strnncollsp_simple_nopad(CHARSET_INFO * cs,
                                 const uchar *a, size_t a_length,
                                 const uchar *b, size_t b_length)
@@ -2095,6 +2107,7 @@ MY_COLLATION_HANDLER my_collation_8bit_simple_ci_handler =
     my_coll_init_simple,	/* init */
     my_strnncoll_simple,
     my_strnncollsp_simple,
+    my_strnncollsp_nchars_simple,
     my_strnxfrm_simple,
     my_strnxfrmlen_simple,
     my_like_range_simple,
@@ -2111,6 +2124,7 @@ MY_COLLATION_HANDLER my_collation_8bit_simple_nopad_ci_handler =
     my_coll_init_simple,	/* init */
     my_strnncoll_simple,
     my_strnncollsp_simple_nopad,
+    my_strnncollsp_nchars_generic_8bit,
     my_strnxfrm_simple_nopad,
     my_strnxfrmlen_simple,
     my_like_range_simple,
diff --git a/strings/ctype-sjis.c b/strings/ctype-sjis.c
index 902034b435d..bd2bf432a34 100644
--- a/strings/ctype-sjis.c
+++ b/strings/ctype-sjis.c
@@ -34046,6 +34046,7 @@ static MY_COLLATION_HANDLER my_collation_handler_sjis_japanese_ci=
   NULL,                 /* init */
   my_strnncoll_sjis_japanese_ci,
   my_strnncollsp_sjis_japanese_ci,
+  my_strnncollsp_nchars_sjis_japanese_ci,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34062,6 +34063,7 @@ static MY_COLLATION_HANDLER my_collation_handler_sjis_bin=
   NULL,                 /* init */
   my_strnncoll_sjis_bin,
   my_strnncollsp_sjis_bin,
+  my_strnncollsp_nchars_sjis_bin,
   my_strnxfrm_mb,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34078,6 +34080,7 @@ static MY_COLLATION_HANDLER my_collation_handler_sjis_japanese_nopad_ci=
   NULL,                 /* init */
   my_strnncoll_sjis_japanese_ci,
   my_strnncollsp_sjis_japanese_nopad_ci,
+  my_strnncollsp_nchars_sjis_japanese_nopad_ci,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
@@ -34094,6 +34097,7 @@ static MY_COLLATION_HANDLER my_collation_handler_sjis_nopad_bin=
   NULL,                 /* init */
   my_strnncoll_sjis_bin,
   my_strnncollsp_sjis_nopad_bin,
+  my_strnncollsp_nchars_sjis_nopad_bin,
   my_strnxfrm_mb_nopad,
   my_strnxfrmlen_simple,
   my_like_range_mb,
diff --git a/strings/ctype-tis620.c b/strings/ctype-tis620.c
index afc5771d6c5..1013922b0f9 100644
--- a/strings/ctype-tis620.c
+++ b/strings/ctype-tis620.c
@@ -852,6 +852,7 @@ static MY_COLLATION_HANDLER my_collation_ci_handler =
     NULL,		/* init */
     my_strnncoll_tis620,
     my_strnncollsp_tis620,
+    my_strnncollsp_nchars_generic_8bit,
     my_strnxfrm_tis620,
     my_strnxfrmlen_simple,
     my_like_range_simple,
@@ -867,6 +868,7 @@ static MY_COLLATION_HANDLER my_collation_nopad_ci_handler =
     NULL,		/* init */
     my_strnncoll_tis620,
     my_strnncollsp_tis620_nopad,
+    my_strnncollsp_nchars_generic_8bit,
     my_strnxfrm_tis620_nopad,
     my_strnxfrmlen_simple,
     my_like_range_simple,
diff --git a/strings/ctype-uca.c b/strings/ctype-uca.c
index 5fbbbec7874..6f505c1394a 100644
--- a/strings/ctype-uca.c
+++ b/strings/ctype-uca.c
@@ -34466,6 +34466,7 @@ MY_COLLATION_HANDLER my_collation_mb_uca_nopad_handler =
     my_coll_init_uca,
     my_strnncoll_any_uca,
     my_strnncollsp_generic_uca_nopad,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_generic_uca_nopad,
     my_strnxfrmlen_any_uca,
     my_like_range_mb,
@@ -34483,6 +34484,7 @@ MY_COLLATION_HANDLER my_collation_generic_uca_nopad_handler =
     my_coll_init_uca,
     my_strnncoll_any_uca,
     my_strnncollsp_generic_uca_nopad,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_generic_uca_nopad,
     my_strnxfrmlen_any_uca,
     my_like_range_generic,
@@ -34499,6 +34501,7 @@ MY_COLLATION_HANDLER my_collation_any_uca_handler_multilevel=
     my_coll_init_uca,
     my_strnncoll_any_uca_multilevel,
     my_strnncollsp_any_uca_multilevel,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_any_uca_multilevel,
     my_strnxfrmlen_any_uca_multilevel,
     my_like_range_generic,
@@ -34515,6 +34518,7 @@ MY_COLLATION_HANDLER my_collation_generic_uca_nopad_handler_multilevel =
     my_coll_init_uca,
     my_strnncoll_any_uca_multilevel,
     my_strnncollsp_generic_uca_nopad_multilevel,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_any_uca_multilevel,
     my_strnxfrmlen_any_uca_multilevel,
     my_like_range_generic,
@@ -34566,6 +34570,7 @@ MY_COLLATION_HANDLER my_collation_ucs2_uca_handler =
   my_coll_init_uca,	/* init */
   my_strnncoll_ucs2_uca,
   my_strnncollsp_ucs2_uca,
+  my_strnncollsp_nchars_generic,
   my_strnxfrm_ucs2_uca,
   my_strnxfrmlen_any_uca,
   my_like_range_generic,
@@ -35531,6 +35536,7 @@ MY_COLLATION_HANDLER my_collation_any_uca_handler =
     my_coll_init_uca,	/* init */
     my_strnncoll_any_uca,
     my_strnncollsp_any_uca,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_any_uca,
     my_strnxfrmlen_any_uca,
     my_like_range_mb,
@@ -37465,6 +37471,7 @@ MY_COLLATION_HANDLER my_collation_utf32_uca_handler =
     my_coll_init_uca,        /* init */
     my_strnncoll_any_uca,
     my_strnncollsp_any_uca,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_any_uca,
     my_strnxfrmlen_any_uca,
     my_like_range_generic,
@@ -38430,6 +38437,7 @@ MY_COLLATION_HANDLER my_collation_utf16_uca_handler =
     my_coll_init_uca,        /* init */
     my_strnncoll_any_uca,
     my_strnncollsp_any_uca,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_any_uca,
     my_strnxfrmlen_any_uca,
     my_like_range_generic,
diff --git a/strings/ctype-ucs2.c b/strings/ctype-ucs2.c
index 48e9f501cd9..4a3fa813a8d 100644
--- a/strings/ctype-ucs2.c
+++ b/strings/ctype-ucs2.c
@@ -1549,6 +1549,7 @@ static MY_COLLATION_HANDLER my_collation_utf16_general_ci_handler =
   NULL,                /* init */
   my_strnncoll_utf16_general_ci,
   my_strnncollsp_utf16_general_ci,
+  my_strnncollsp_nchars_utf16_general_ci,
   my_strnxfrm_unicode,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -1565,6 +1566,7 @@ static MY_COLLATION_HANDLER my_collation_utf16_bin_handler =
   NULL,                /* init */
   my_strnncoll_utf16_bin,
   my_strnncollsp_utf16_bin,
+  my_strnncollsp_nchars_utf16_bin,
   my_strnxfrm_unicode_full_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -1581,6 +1583,7 @@ static MY_COLLATION_HANDLER my_collation_utf16_general_nopad_ci_handler =
   NULL,                /* init */
   my_strnncoll_utf16_general_ci,
   my_strnncollsp_utf16_general_nopad_ci,
+  my_strnncollsp_nchars_utf16_general_nopad_ci,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -1597,6 +1600,7 @@ static MY_COLLATION_HANDLER my_collation_utf16_nopad_bin_handler =
   NULL,                /* init */
   my_strnncoll_utf16_bin,
   my_strnncollsp_utf16_nopad_bin,
+  my_strnncollsp_nchars_utf16_nopad_bin,
   my_strnxfrm_unicode_full_nopad_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -1882,6 +1886,7 @@ static MY_COLLATION_HANDLER my_collation_utf16le_general_ci_handler =
   NULL,                /* init */
   my_strnncoll_utf16le_general_ci,
   my_strnncollsp_utf16le_general_ci,
+  my_strnncollsp_nchars_utf16le_general_ci,
   my_strnxfrm_unicode,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -1898,6 +1903,7 @@ static MY_COLLATION_HANDLER my_collation_utf16le_bin_handler =
   NULL,                /* init */
   my_strnncoll_utf16le_bin,
   my_strnncollsp_utf16le_bin,
+  my_strnncollsp_nchars_utf16le_bin,
   my_strnxfrm_unicode_full_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -1914,6 +1920,7 @@ static MY_COLLATION_HANDLER my_collation_utf16le_general_nopad_ci_handler =
   NULL,                /* init */
   my_strnncoll_utf16le_general_ci,
   my_strnncollsp_utf16le_general_nopad_ci,
+  my_strnncollsp_nchars_utf16le_general_nopad_ci,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -1930,6 +1937,7 @@ static MY_COLLATION_HANDLER my_collation_utf16le_nopad_bin_handler =
   NULL,                /* init */
   my_strnncoll_utf16le_bin,
   my_strnncollsp_utf16le_nopad_bin,
+  my_strnncollsp_nchars_utf16le_nopad_bin,
   my_strnxfrm_unicode_full_nopad_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -2704,6 +2712,7 @@ static MY_COLLATION_HANDLER my_collation_utf32_general_ci_handler =
   NULL, /* init */
   my_strnncoll_utf32_general_ci,
   my_strnncollsp_utf32_general_ci,
+  my_strnncollsp_nchars_utf32_general_ci,
   my_strnxfrm_unicode,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -2720,6 +2729,7 @@ static MY_COLLATION_HANDLER my_collation_utf32_bin_handler =
   NULL, /* init */
   my_strnncoll_utf32_bin,
   my_strnncollsp_utf32_bin,
+  my_strnncollsp_nchars_utf32_bin,
   my_strnxfrm_unicode_full_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -2736,6 +2746,7 @@ static MY_COLLATION_HANDLER my_collation_utf32_general_nopad_ci_handler =
   NULL, /* init */
   my_strnncoll_utf32_general_ci,
   my_strnncollsp_utf32_general_nopad_ci,
+  my_strnncollsp_nchars_utf32_general_nopad_ci,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_generic,
@@ -2752,6 +2763,7 @@ static MY_COLLATION_HANDLER my_collation_utf32_nopad_bin_handler =
   NULL, /* init */
   my_strnncoll_utf32_bin,
   my_strnncollsp_utf32_nopad_bin,
+  my_strnncollsp_nchars_utf32_nopad_bin,
   my_strnxfrm_unicode_full_nopad_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_generic,
@@ -3286,6 +3298,7 @@ static MY_COLLATION_HANDLER my_collation_ucs2_general_ci_handler =
     NULL,		/* init */
     my_strnncoll_ucs2_general_ci,
     my_strnncollsp_ucs2_general_ci,
+    my_strnncollsp_nchars_ucs2_general_ci,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_generic,
@@ -3302,6 +3315,7 @@ static MY_COLLATION_HANDLER my_collation_ucs2_bin_handler =
     NULL,		/* init */
     my_strnncoll_ucs2_bin,
     my_strnncollsp_ucs2_bin,
+    my_strnncollsp_nchars_ucs2_bin,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_generic,
@@ -3318,6 +3332,7 @@ static MY_COLLATION_HANDLER my_collation_ucs2_general_nopad_ci_handler =
     NULL,		/* init */
     my_strnncoll_ucs2_general_ci,
     my_strnncollsp_ucs2_general_nopad_ci,
+    my_strnncollsp_nchars_ucs2_general_nopad_ci,
     my_strnxfrm_unicode_nopad,
     my_strnxfrmlen_unicode,
     my_like_range_generic,
@@ -3334,6 +3349,7 @@ static MY_COLLATION_HANDLER my_collation_ucs2_nopad_bin_handler =
     NULL,		/* init */
     my_strnncoll_ucs2_bin,
     my_strnncollsp_ucs2_nopad_bin,
+    my_strnncollsp_nchars_ucs2_nopad_bin,
     my_strnxfrm_unicode_nopad,
     my_strnxfrmlen_unicode,
     my_like_range_generic,
diff --git a/strings/ctype-ujis.c b/strings/ctype-ujis.c
index 949f3aadc36..34600eda1a5 100644
--- a/strings/ctype-ujis.c
+++ b/strings/ctype-ujis.c
@@ -67239,6 +67239,7 @@ static MY_COLLATION_HANDLER my_collation_ujis_japanese_ci_handler =
     NULL,		/* init */
     my_strnncoll_ujis_japanese_ci,
     my_strnncollsp_ujis_japanese_ci,
+    my_strnncollsp_nchars_ujis_japanese_ci,
     my_strnxfrm_mb,     /* strnxfrm     */
     my_strnxfrmlen_simple,
     my_like_range_mb,   /* like_range   */
@@ -67255,6 +67256,7 @@ static MY_COLLATION_HANDLER my_collation_ujis_bin_handler =
     NULL,                    /* init */
     my_strnncoll_ujis_bin,
     my_strnncollsp_ujis_bin,
+    my_strnncollsp_nchars_ujis_bin,
     my_strnxfrm_mb,
     my_strnxfrmlen_simple,
     my_like_range_mb,
@@ -67271,6 +67273,7 @@ static MY_COLLATION_HANDLER my_collation_ujis_japanese_nopad_ci_handler =
     NULL,                    /* init */
     my_strnncoll_ujis_japanese_ci,
     my_strnncollsp_ujis_japanese_nopad_ci,
+    my_strnncollsp_nchars_ujis_japanese_nopad_ci,
     my_strnxfrm_mb_nopad,
     my_strnxfrmlen_simple,
     my_like_range_mb,
@@ -67287,6 +67290,7 @@ static MY_COLLATION_HANDLER my_collation_ujis_nopad_bin_handler =
     NULL,                    /* init */
     my_strnncoll_ujis_bin,
     my_strnncollsp_ujis_nopad_bin,
+    my_strnncollsp_nchars_ujis_nopad_bin,
     my_strnxfrm_mb_nopad,
     my_strnxfrmlen_simple,
     my_like_range_mb,
diff --git a/strings/ctype-utf8.c b/strings/ctype-utf8.c
index 1d0295000e4..5ab9007c81d 100644
--- a/strings/ctype-utf8.c
+++ b/strings/ctype-utf8.c
@@ -5532,6 +5532,7 @@ static MY_COLLATION_HANDLER my_collation_utf8_general_ci_handler =
     NULL,               /* init */
     my_strnncoll_utf8_general_ci,
     my_strnncollsp_utf8_general_ci,
+    my_strnncollsp_nchars_utf8_general_ci,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_mb,
@@ -5548,6 +5549,7 @@ static MY_COLLATION_HANDLER my_collation_utf8_general_mysql500_ci_handler =
     NULL,               /* init */
     my_strnncoll_utf8_general_mysql500_ci,
     my_strnncollsp_utf8_general_mysql500_ci,
+    my_strnncollsp_nchars_utf8_general_mysql500_ci,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_mb,
@@ -5564,6 +5566,7 @@ static MY_COLLATION_HANDLER my_collation_utf8_bin_handler =
     NULL,		/* init */
     my_strnncoll_utf8_bin,
     my_strnncollsp_utf8_bin,
+    my_strnncollsp_nchars_utf8_bin,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_mb,
@@ -5580,6 +5583,7 @@ static MY_COLLATION_HANDLER my_collation_utf8_general_nopad_ci_handler =
   NULL,               /* init */
   my_strnncoll_utf8_general_ci,
   my_strnncollsp_utf8_general_nopad_ci,
+  my_strnncollsp_nchars_utf8_general_nopad_ci,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_mb,
@@ -5596,6 +5600,7 @@ static MY_COLLATION_HANDLER my_collation_utf8_nopad_bin_handler =
   NULL,		/* init */
   my_strnncoll_utf8_bin,
   my_strnncollsp_utf8_nopad_bin,
+  my_strnncollsp_nchars_utf8_nopad_bin,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_mb,
@@ -5925,6 +5930,7 @@ static MY_COLLATION_HANDLER my_collation_cs_handler =
     NULL,		/* init */
     my_strnncoll_utf8_cs,
     my_strnncollsp_utf8_cs,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_simple,
@@ -7216,6 +7222,7 @@ static MY_COLLATION_HANDLER my_collation_filename_handler =
     NULL,               /* init */
     my_strnncoll_simple,
     my_strnncollsp_simple,
+    my_strnncollsp_nchars_generic,
     my_strnxfrm_unicode,
     my_strnxfrmlen_unicode,
     my_like_range_mb,
@@ -7893,6 +7900,7 @@ static MY_COLLATION_HANDLER my_collation_utf8mb4_general_ci_handler=
   NULL,               /* init */
   my_strnncoll_utf8mb4_general_ci,
   my_strnncollsp_utf8mb4_general_ci,
+  my_strnncollsp_nchars_utf8mb4_general_ci,
   my_strnxfrm_unicode,
   my_strnxfrmlen_unicode,
   my_like_range_mb,
@@ -7909,6 +7917,7 @@ static MY_COLLATION_HANDLER my_collation_utf8mb4_bin_handler =
     NULL,              /* init */
     my_strnncoll_utf8mb4_bin,
     my_strnncollsp_utf8mb4_bin,
+    my_strnncollsp_nchars_utf8mb4_bin,
     my_strnxfrm_unicode_full_bin,
     my_strnxfrmlen_unicode_full_bin,
     my_like_range_mb,
@@ -7925,6 +7934,7 @@ static MY_COLLATION_HANDLER my_collation_utf8mb4_general_nopad_ci_handler=
   NULL,               /* init */
   my_strnncoll_utf8mb4_general_ci,
   my_strnncollsp_utf8mb4_general_nopad_ci,
+  my_strnncollsp_nchars_utf8mb4_general_nopad_ci,
   my_strnxfrm_unicode_nopad,
   my_strnxfrmlen_unicode,
   my_like_range_mb,
@@ -7941,6 +7951,7 @@ static MY_COLLATION_HANDLER my_collation_utf8mb4_nopad_bin_handler =
   NULL,		/* init */
   my_strnncoll_utf8mb4_bin,
   my_strnncollsp_utf8mb4_nopad_bin,
+  my_strnncollsp_nchars_utf8mb4_nopad_bin,
   my_strnxfrm_unicode_full_nopad_bin,
   my_strnxfrmlen_unicode_full_bin,
   my_like_range_mb,
diff --git a/strings/ctype-win1250ch.c b/strings/ctype-win1250ch.c
index f33a83294d6..15fa6299e4e 100644
--- a/strings/ctype-win1250ch.c
+++ b/strings/ctype-win1250ch.c
@@ -674,6 +674,7 @@ static MY_COLLATION_HANDLER my_collation_czech_ci_handler =
   NULL,				/* init */
   my_strnncoll_win1250ch,
   my_strnncollsp_win1250ch,
+  my_strnncollsp_nchars_generic_8bit,
   my_strnxfrm_win1250ch,
   my_strnxfrmlen_simple,
   my_like_range_win1250ch,
diff --git a/strings/ctype.c b/strings/ctype.c
index 32c41e6e9e7..b396ef53b12 100644
--- a/strings/ctype.c
+++ b/strings/ctype.c
@@ -1210,3 +1210,30 @@ outp:
   copy_status->m_source_end_pos= from;
   return to - to_start;
 }
+
+
+int my_strnncollsp_nchars_generic(CHARSET_INFO *cs,
+                                  const uchar *str1, size_t len1,
+                                  const uchar *str2, size_t len2,
+                                  size_t nchars)
+{
+  int error;
+  len1= my_well_formed_length(cs, (const char *) str1,
+                                  (const char *) str1 + len1,
+                                  nchars, &error);
+  len2= my_well_formed_length(cs, (const char *) str2,
+                                  (const char *) str2 + len2,
+                                  nchars, &error);
+  return cs->coll->strnncollsp(cs, str1, len1, str2, len2);
+}
+
+
+int my_strnncollsp_nchars_generic_8bit(CHARSET_INFO *cs,
+                                       const uchar *str1, size_t len1,
+                                       const uchar *str2, size_t len2,
+                                       size_t nchars)
+{
+  set_if_smaller(len1, nchars);
+  set_if_smaller(len2, nchars);
+  return cs->coll->strnncollsp(cs, str1, len1, str2, len2);
+}
diff --git a/strings/strcoll.ic b/strings/strcoll.ic
index eb5b3d5fe9b..ac041512735 100644
--- a/strings/strcoll.ic
+++ b/strings/strcoll.ic
@@ -221,6 +221,67 @@ MY_FUNCTION_NAME(strnncollsp)(CHARSET_INFO *cs __attribute__((unused)),
 {
   return MY_FUNCTION_NAME(strnncoll)(cs, a, a_length, b, b_length, FALSE);
 }
+
+/**
+  Compare two strings according to the collation,
+  using the NOPAD comparison style.
+
+  @param cs          - the character set and collation
+  @param a           - the left string
+  @param a_length    - the length of the left string
+  @param b           - the right string
+  @param b_length    - the length of the right string
+  @param nchars      - compare this amount of characters only
+  @return            - the comparison result
+*/
+static int
+MY_FUNCTION_NAME(strnncollsp_nchars)(CHARSET_INFO *cs __attribute__((unused)),
+                                     const uchar *a, size_t a_length,
+                                     const uchar *b, size_t b_length,
+                                     size_t nchars)
+{
+  const uchar *a_end= a + a_length;
+  const uchar *b_end= b + b_length;
+  for ( ; ; nchars--)
+  {
+    int a_weight, b_weight, res;
+    uint a_wlen, b_wlen;
+
+    if (!nchars)
+      return 0;
+
+    a_wlen= MY_FUNCTION_NAME(scan_weight)(&a_weight, a, a_end);
+    b_wlen= MY_FUNCTION_NAME(scan_weight)(&b_weight, b, b_end);
+    /*
+      a_wlen  b_wlen Comment
+      ------  ------ -------
+      0       0      Strings ended simultaneously, "a" and "b" are equal.
+      0       >0     "a" is a prefix of "b", so "a" is smaller.
+      >0      0      "b" is a prefix of "a", so "b" is smaller.
+      >0      >0     Two weights were scanned, check weight difference.
+    */
+    if (!a_wlen)
+      return b_wlen ? -b_weight : 0;
+
+    if (!b_wlen)
+      return a_weight;
+
+    if ((res= (a_weight - b_weight)))
+      return res;
+    /*
+      None of the strings has ended yet.
+    */
+    DBUG_ASSERT(a < a_end);
+    DBUG_ASSERT(b < b_end);
+    a+= a_wlen;
+    b+= b_wlen;
+  }
+  DBUG_ASSERT(0);
+  return 0;
+}
+
+
+
 #else
 /**
   Compare two strings according to the collation, with PAD SPACE handling.
@@ -276,6 +337,58 @@ MY_FUNCTION_NAME(strnncollsp)(CHARSET_INFO *cs __attribute__((unused)),
   DBUG_ASSERT(0);
   return 0;
 }
+
+/**
+  Compare two strings according to the collation, with nchars limit,
+  with PAD SPACE comparison style.
+
+  @param cs          - the character set and collation
+  @param a           - the left string
+  @param a_length    - the length of the left string
+  @param b           - the right string
+  @param b_length    - the length of the right string
+  @param nchars      - compare this amount of characters only
+  @return            - the comparison result
+*/
+static int
+MY_FUNCTION_NAME(strnncollsp_nchars)(CHARSET_INFO *cs __attribute__((unused)),
+                                     const uchar *a, size_t a_length,
+                                     const uchar *b, size_t b_length,
+                                     size_t nchars)
+{
+  const uchar *a_end= a + a_length;
+  const uchar *b_end= b + b_length;
+  for ( ; ; nchars--)
+  {
+    int a_weight, b_weight, res;
+    uint a_wlen, b_wlen;
+    if (!nchars)
+      return 0;
+    a_wlen= MY_FUNCTION_NAME(scan_weight)(&a_weight, a, a_end);
+    b_wlen= MY_FUNCTION_NAME(scan_weight)(&b_weight, b, b_end);
+    if ((res= (a_weight - b_weight)))
+    {
+      /* Got two different weights. See comments in strnncollsp above. */
+      return res;
+    }
+    if (!a_wlen && !b_wlen)
+    {
+      /* Got two auto-generated trailing spaces. */
+      DBUG_ASSERT(a == a_end);
+      DBUG_ASSERT(b == b_end);
+      return 0;
+    }
+    /*
+      At least one of the strings has not ended yet, continue comparison.
+    */
+    DBUG_ASSERT(a < a_end || b < b_end);
+    a+= a_wlen;
+    b+= b_wlen;
+  }
+  DBUG_ASSERT(0);
+  return 0;
+}
+
 #endif
 
 
diff --git a/strings/strings_def.h b/strings/strings_def.h
index b3727321e19..8bf089ec695 100644
--- a/strings/strings_def.h
+++ b/strings/strings_def.h
@@ -105,6 +105,16 @@ static inline const uchar *skip_trailing_space(const uchar *ptr,size_t len)
 }
 
 
+int my_strnncollsp_nchars_generic(CHARSET_INFO *cs,
+                                  const uchar *str1, size_t len1,
+                                  const uchar *str2, size_t len2,
+                                  size_t nchars);
+
+int my_strnncollsp_nchars_generic_8bit(CHARSET_INFO *cs,
+                                       const uchar *str1, size_t len1,
+                                       const uchar *str2, size_t len2,
+                                       size_t nchars);
+
 uint my_8bit_charset_flags_from_data(CHARSET_INFO *cs);
 uint my_8bit_collation_flags_from_data(CHARSET_INFO *cs);