Update item:

Update item:

< * Implement dirty reads or shared row locks and use them in RI triggers (?)
> * Implement dirty reads or shared row locks and use them in RI triggers
>
>   Adding shared locks requires recording the table/rows numbers in a
>   shared area, and this could potentially be a large amount of data.
>   One idea is to store the table/row numbers in a separate table and set
>   a bit on the row indicating looking in this new table is required to
>   find any shared row locks.
>