Prev Next

Database / Mnesia basics Interview questions

What are the Mnesia table types (set, ordered_set, bag)?

The type option on mnesia:create_table/2 controls how a table handles keys and ordering, mirroring the same distinction ETS makes.

setordered_setbag
Unique keys; one record per key. Default type. Unique keys, kept in a sorted order for efficient range-style traversal. Keys may repeat; multiple distinct records can share the same key.
mnesia:create_table(tag,
    [{attributes, [item_id, tag_name]},
     {type, bag}]).   %% one item_id can have many tag_name entries

set is the right default for most tables where each key genuinely identifies one row. bag fits naturally modeled one-to-many relationships (an item with multiple tags) without a separate join table. ordered_set is chosen specifically when you need to iterate keys in sorted order efficiently.

Which Mnesia table type allows multiple distinct records to share the same key?
What is the default table type if you don't specify one?

More Related questions...

What is Mnesia? What is a Mnesia table? What are the storage types available for a Mnesia table? What is a Mnesia schema? How do you create a Mnesia schema? How do you create a Mnesia table? What is a Mnesia transaction? How do you write a record to a Mnesia table? How do you read a record from a Mnesia table? What are dirty operations in Mnesia? What is mnesia:dirty_read/1? What is a Mnesia record? How do you delete a record from a Mnesia table? What is the purpose of mnesia:start/0? How do you stop Mnesia? What are the Mnesia table types (set, ordered_set, bag)? What is a Mnesia index? How do you add a secondary index to a Mnesia table? What is mnesia:info/0 used for? How do you check if Mnesia is running? What is the Mnesia directory (Mnesia.dir)? What is the primary key in a Mnesia table? What is mnesia:select/2 used for? What is record_info used for when creating a Mnesia table? What are the attributes of a Mnesia table? What is a Mnesia node? How do you replicate a table across multiple Mnesia nodes? What is mnesia:table_info/2 used for? Describe the difference between a Mnesia table and an ETS table? Why should Mnesia operations generally run inside a transaction? When should you use dirty operations instead of a transaction? What is the difference between ram_copies and disc_copies? What is disc_only_copies and when would you use it? What happens to a disc_copies table when its node restarts? How do you change a table's storage type at runtime? What is a Mnesia table lock and how does it work? How does Mnesia keep replicated tables consistent across nodes? How do you migrate a Mnesia record definition when its fields change? What is mnesia:transform_table/3 used for? When should you choose bag over set for a Mnesia table? How do you back up a Mnesia database? How do you restore a Mnesia database from a backup? Explain the lifecycle of a Mnesia transaction from start to commit? How do you troubleshoot a Mnesia table stuck in the "loading" state? What is mnesia:force_load_table/1 and when should you use it? What is the difference between mnesia:read/1 and mnesia:wread/1? What is a Mnesia checkpoint used for? How does Mnesia resolve conflicts after a network partition heals?
Show more question and Answers...

Mnesia intermediate to advanced Interview questions

Comments & Discussions

Interviews Questions

About Javapedia.net

Javapedia.net is for Java and J2EE developers, technologist and college students who prepare of interview. Also this site includes many practical examples.

This site is developed using J2EE technologies by Steve Antony, a senior Developer/lead at one of the logistics based company.

Follow Javapedia updates

contact: javatutorials2016[at]gmail[dot]com

Kindly consider donating for maintaining this website. Thanks.

Copyright © 2026, javapedia.net, all rights reserved. · .

DMCA.com Protection Status