MDEV-8362 dash '-' is not recognized in charset armscii8 on select where query

1 files changed, 22 insertions, 1 deletions

diff --git a/strings/ctype-simple.c b/strings/ctype-simple.c
index d7a1b3f33b4..394924c8209 100644
--- a/strings/ctype-simple.c
+++ b/strings/ctype-simple.c
@@ -1303,7 +1303,28 @@ create_fromuni(struct charset_info_st *cs,
       if (wc >= idx[i].uidx.from && wc <= idx[i].uidx.to && wc)
       {
         int ofs= wc - idx[i].uidx.from;
-        tab[ofs]= ch;
+        if (!tab[ofs] || tab[ofs] > 0x7F) /* Prefer ASCII*/
+        {
+          /*
+            Some character sets can have double encoding. For example,
+            in ARMSCII8, the following characters are encoded twice:
+
+            Encoding#1 Encoding#2 Unicode Character Name
+            ---------- ---------- ------- --------------
+            0x27       0xFF       U+0027  APOSTROPHE
+            0x28       0xA5       U+0028  LEFT PARENTHESIS
+            0x29       0xA4       U+0029  RIGHT PARENTHESIS
+            0x2C       0xAB       U+002C  COMMA
+            0x2D       0xAC       U+002D  HYPHEN-MINUS
+            0x2E       0xA9       U+002E  FULL STOP
+
+            That is, both 0x27 and 0xFF convert to Unicode U+0027.
+            When converting back from Unicode to ARMSCII,
+            we prefer the ASCII range, that is we want U+0027
+            to convert to 0x27 rather than to 0xFF.
+          */
+          tab[ofs]= ch;
+        }
       }
     }
   }