maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Sachin!

I suspect is_null() could be wrong here.

Please, add a test case where a table has a BEFORE UPDATE trigger
and a long UNIQUE over a NOT NULL field.

And see how cmp_binary_offset() is used in compare_record(), for
example.

On Oct 08, Sachin Setiya wrote:
> revision-id: 56f2b3d12b6 (mariadb-10.4.11-385-g56f2b3d12b6)
> parent(s): af834c218a5
> author: Sachin Setiya <sachin.setiya@xxxxxxxxxxx>
> committer: Sachin Setiya <sachin.setiya@xxxxxxxxxxx>
> timestamp: 2020-09-14 20:08:18 +0100
> message:
> 
> MDEV-23264 Unique blobs allow duplicate values upon UPDATE
> 
> Problem:-
>   We are able to insert duplicate value in table because cmp_binary_offset
>   is not able to differentiate between NULL and empty string. So
>   check_duplicate_long_entry_key is never called and we don't check for
>   duplicate.
> Solution
>   Added a if condition with is_null() on field which can differentiate
>   between NULL and empty string.
> 
> diff --git a/sql/handler.cc b/sql/handler.cc
> index 40dea349272..71e6a904f23 100644
> --- a/sql/handler.cc
> +++ b/sql/handler.cc
> @@ -6699,8 +6699,13 @@ static int check_duplicate_long_entries_update(TABLE *table, handler *h, uchar *
>        for (uint j= 0; j < key_parts; j++, keypart++)
>        {
>          field= keypart->field;
> -        /* Compare fields if they are different then check for duplicates*/
> -        if(field->cmp_binary_offset(reclength))
> +        /*
> +          Compare fields if they are different then check for duplicates
> +          cmp_binary_offset cannot differentiate between null and empty string
> +          So also check for that too
> +        */
> +        if((field->is_null(0) != field->is_null(reclength)) ||
> +                               field->cmp_binary_offset(reclength))
>          {
>            if((error= check_duplicate_long_entry_key(table, table->update_handler,
>                                                   new_rec, i)))
> 
Regards,
Sergei
VP of MariaDB Server Engineering
and security@xxxxxxxxxxx