Database / Mnesia basics Interview questions
How do you add a secondary index to a Mnesia table?
mnesia:add_table_index/2 adds an index on a given attribute of an already-existing table,
which can be done at runtime, even while the system is live and serving traffic.
mnesia:add_table_index(person, age).
Once added, queries using mnesia:index_read(Table, Value, Attribute) can look up records by
that attribute's value directly. Building the index does require scanning the existing table once to populate
it, so adding an index on a very large, already-populated table is a heavier one-time operation than adding it
to an empty table up front as part of initial schema design.
Can you add a table index to an already-populated Mnesia table at runtime?
What one-time cost does adding an index to a large existing table incur?
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