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Re^5: [OT] MySQL recalibrating a sort-index

by erix (Parson)
on Feb 17, 2018 at 08:13 UTC ( #1209376=note: print w/replies, xml ) Need Help??


in reply to Re^4: [OT] MySQL recalibrating a sort-index
in thread [OT] MySQL recalibrating a sort-index

Ah, you were looking for a DEFERRABLE CONSTRAINT, which postpones the constraint-validation to the end of a transaction.

So, you'd do (again, postgres):

create table tree ( f_node_id int primary key , f_parent_id int , f_name text , f_sort float , constraint tree_parent_sort_uniq_idx unique (f_parent_id, f_sort) d +eferrable );

This lets you mess about with non-unique states for the duration of a transaction. The constraint (here: uniqueness) is only then enforced.

I can't imagine MariaDB does not have this functionality but I can't find it in the documentation. (I looked for DEFERRED or DEFERRABLE. The MariaDB docs list 'DEFERRED' as a reserved word but I see no functionality associated with it.)

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Re^6: [OT] MySQL recalibrating a sort-index
by LanX (Archbishop) on Feb 17, 2018 at 10:03 UTC

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