Bug#21205695 DROP TABLE MAY CAUSE SLAVES TO BREAK

    Problem:
    ========
    1) Drop table queries are re-generated by server
    before writing the events(queries) into binlog
    for various reasons. If table name/db name contains
    a non regular characters (like latin characters),
    the generated query is wrong. Hence it breaks the
    replication.
    2) In the edge case, when table name/db name contains
    64 characters, server is throwing an assert
    assert(M_TBLLEN < 128)
    3) In the edge case, when db name contains 64 latin
    characters, binlog content is interpreted badly
    which is leading replication failure.

    Analysis & Fix :
    ================
    1) Parser reads the table name from the query and converts
    it to standard charset(utf8) and stores it in table_name variable.
    When drop table query is regenerated with the same table_name
    variable, it should be converted back to the original charset
    from standard charset(utf8).

    2) Latin character takes two bytes for each character. Limit
    of the identifier is 64. SYSTEM_CHARSET_MBMAXLEN is set to '3'.
    So there is a possiblity that tablename/dbname contains 3 * 64.
    Hence assert is changed to
    (M_TBLLEN <= NAME_CHAR_LEN*SYSTEM_CHARSET_MBMAXLEN)

    3) db_len in the binlog event header is taking 1 byte.
       db_len is ranged from 0 to 192 bytes (3 * 64).
       While reading the db_len from the event, server
       is casting to uint instead of uchar which is leading
       to bad db_len. This problem is fixed by changing the
       cast type to uchar.

1 files changed, 8 insertions, 2 deletions

diff --git a/sql/sql_show.h b/sql/sql_show.h
index 16bfc5cdb69..ad6494fd7d4 100644
--- a/sql/sql_show.h
+++ b/sql/sql_show.h
@@ -92,8 +92,14 @@ int view_store_create_info(THD *thd, TABLE_LIST *table, String *buff);
 int copy_event_to_schema_table(THD *thd, TABLE *sch_table, TABLE *event_table);
 int get_quote_char_for_identifier(THD *thd, const char *name, uint length);
 
-void append_identifier(THD *thd, String *packet, const char *name,
-		       uint length);
+void append_identifier(THD *thd, String *packet, const char *name, uint length,
+                       CHARSET_INFO *from_cs, CHARSET_INFO *to_cs);
+inline void append_identifier(THD *thd, String *packet, const char *name,
+                              uint length)
+{
+  append_identifier(thd, packet, name, length, NULL, NULL);
+}
+
 void mysqld_list_fields(THD *thd,TABLE_LIST *table, const char *wild);
 int mysqld_dump_create_info(THD *thd, TABLE_LIST *table_list, int fd);
 bool mysqld_show_create(THD *thd, TABLE_LIST *table_list);