CONVERT_CHARSET_PARTITION_CONSTANT:
               SQL/SQL_PARTITION..CC:202

Issue:
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This problem happens under the following conditions:
1) A table partitioned with a character column as the key.
2) The expressions specified in the partition definition
   requires a charset conversion. This can happen when the
   server's default collation is different from the
   expression's collation.
3) INSERT DELAYED is used to insert data into the table.

SOLUTION:
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While creating the delayed_insert object, initialize it
with the relevant select_lex.