PROBLEM
-------

1) Collation change on the column is a inplace alter operation.(if no index on the column)
2) The column information is stored in dict_table_t->cols[] array
   which is a in memory structure.
3) During inplace alter, the collation is changed in the DD table
   but innodb ignores the collation change since there is no change
   in data ,but it is necessary to change it in the in memory
   object dict_table_t->col[].prtype,but in this case this was
   only happening with CHAR datatype.
4) So for varchar datatype the memory object is not updated.
   When a index is created on this column , the new index takes
   the column information from the in memory object and copies the
   stale precision type.
5) When the search is made on the index the comparison of data
   happens with the previous collation and may lead to wrong result.

FIX
---

1) For varchar and text datatypes , make sure to update precision
   type in the memory object during inplace commit operation.

RB: #24689
Reviewed by : Debarun Banerjee <debarun.banerjee@oracle.com>