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Bug#21205695 DROP TABLE MAY CAUSE SLAVES TO BREAK

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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.
This commit is contained in:
Venkatesh Duggirala
2015-12-01 15:38:11 +05:30
parent 08e929388b
commit 2735f0b920
6 changed files with 173 additions and 32 deletions
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12
sql/sql_table.cc
View File

@@ -2138,11 +2138,13 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
if (thd->db == NULL || strcmp(db,thd->db) != 0
|| is_drop_tmp_if_exists_added )
{
append_identifier(thd, built_ptr_query, db, db_len);
append_identifier(thd, built_ptr_query, db, db_len,
system_charset_info, thd->charset());
built_ptr_query->append(".");
}
append_identifier(thd, built_ptr_query, table->table_name,
strlen(table->table_name));
strlen(table->table_name), system_charset_info,
thd->charset());
built_ptr_query->append(",");
}
/*
@@ -2204,12 +2206,14 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
*/
if (thd->db == NULL || strcmp(db,thd->db) != 0)
{
append_identifier(thd, &built_query, db, db_len);
append_identifier(thd, &built_query, db, db_len,
system_charset_info, thd->charset());
built_query.append(".");
}
append_identifier(thd, &built_query, table->table_name,
strlen(table->table_name));
strlen(table->table_name), system_charset_info,
thd->charset());
built_query.append(",");
}
}