BUG#37426: RBR breaks for CHAR() UTF-8 fields > 85 chars

      
In order to handle CHAR() fields, 8 bits were reserved for
the size of the CHAR field. However, instead of denoting the
number of characters in the field, field_length was used which
denotes the number of bytes in the field.

Since UTF-8 fields can have three bytes per character (and
has been extended to have four bytes per character in 6.0),
an extra two bits have been encoded in the field metadata
work for fields of type Field_string (i.e., CHAR fields).

Since the metadata word is filled, the extra bits have been
encoded in the upper 4 bits of the real type (the most 
significant byte of the metadata word) by computing the
bitwise xor of the extra two bits. Since the upper 4 bits
of the real type always is 1111 for Field_string, this 
means that for fields of length <256, the encoding is
identical to the encoding used in pre-5.1.26 servers, but
for lengths of 256 or more, an unrecognized type is formed,
causing an old slave (that does not handle lengths of 256
or more) to stop.

1 files changed, 16 insertions, 4 deletions

diff --git a/sql/field.h b/sql/field.h
index 479a71dfee5..6c6cab1e4f0 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -30,6 +30,8 @@ const uint32 max_field_size= (uint32) 4294967295U;
 class Send_field;
 class Protocol;
 class Create_field;
+class Relay_log_info;
+
 struct st_cache_field;
 int field_conv(Field *to,Field *from);
 
@@ -162,7 +164,8 @@ public:
     table, which is located on disk).
   */
   virtual uint32 pack_length_in_rec() const { return pack_length(); }
-  virtual int compatible_field_size(uint field_metadata);
+  virtual int compatible_field_size(uint field_metadata,
+                                    const Relay_log_info *);
   virtual uint pack_length_from_metadata(uint field_metadata)
   { return field_metadata; }
   /*
@@ -716,7 +719,8 @@ public:
   uint32 pack_length() const { return (uint32) bin_size; }
   uint pack_length_from_metadata(uint field_metadata);
   uint row_pack_length() { return pack_length(); }
-  int compatible_field_size(uint field_metadata);
+  int compatible_field_size(uint field_metadata,
+                            const Relay_log_info *rli);
   uint is_equal(Create_field *new_field);
   virtual const uchar *unpack(uchar* to, const uchar *from,
                               uint param_data, bool low_byte_first);
@@ -1425,7 +1429,14 @@ public:
   virtual const uchar *unpack(uchar* to, const uchar *from,
                               uint param_data, bool low_byte_first);
   uint pack_length_from_metadata(uint field_metadata)
-  { return (field_metadata & 0x00ff); }
+  {
+    DBUG_PRINT("debug", ("field_metadata: 0x%04x", field_metadata));
+    if (field_metadata == 0)
+      return row_pack_length();
+    return (((field_metadata >> 4) & 0x300) ^ 0x300) + (field_metadata & 0x00ff);
+  }
+  int compatible_field_size(uint field_metadata,
+                            const Relay_log_info *rli);
   uint row_pack_length() { return (field_length + 1); }
   int pack_cmp(const uchar *a,const uchar *b,uint key_length,
                my_bool insert_or_update);
@@ -1878,7 +1889,8 @@ public:
   uint pack_length_from_metadata(uint field_metadata);
   uint row_pack_length()
   { return (bytes_in_rec + ((bit_len > 0) ? 1 : 0)); }
-  int compatible_field_size(uint field_metadata);
+  int compatible_field_size(uint field_metadata,
+                            const Relay_log_info *rli);
   void sql_type(String &str) const;
   virtual uchar *pack(uchar *to, const uchar *from,
                       uint max_length, bool low_byte_first);