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POis EAV - Hybrid a bad database design choice
 

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  1. POis EAV - Hybrid a bad database design choice
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    <p>We have to redesign a legacy POI database from MySQL to PostgreSQL. Currently all entities have 80-120+ attributes that represent individual properties.</p> <p>We have been asked to consider flexibility as well as good design approach for the new database. However new design should allow:</p> <ul> <li><p><strong><em>n</em></strong> no. of attributes/properties for any entity i.e. no of attributes for any entity are not fixed and may change on regular basis.</p></li> <li><p>allow content admins to add new properties to existing entities <strong>on the fly</strong> using through admin interfaces rather than making changes in db schema all the time.</p></li> </ul> <p>There are quite a few discussions about performance issues of EAV but if we don't go with a hybrid-EAV we end up:</p> <ul> <li>having lot of empty columns (we still go and add new columns even if 99% of the data does not have those properties)</li> <li>spend more time maintaining database esp. when attributes keep changing.</li> <li>no way of allowing content admins to add new properties to existing entities</li> </ul> <p>Anyway here's what we are thinking about the new design (basic ERD included):</p> <ul> <li><p>Have separate tables for each entity containing some basic info that is exclusive e.g. id,name,address,contact,created,etc etc.</p></li> <li><p>Have 2 tables attribute type and attribute to store properties information.</p></li> <li><p>Link each entity to an attribute using a many-to-many relation.</p></li> <li><p>Store addresses in different table and link to entities using foreign key.</p></li> </ul> <p><img src="https://i.stack.imgur.com/VIBk0.png" alt="alt text"></p> <p>We think this will allow us to be more flexible when adding,removing or updating on properties.</p> <p>This design, however, will result in increased number of joins when fetching data e.g.to display all "attributes" for a given stadium we might have a query with 20+ joins to fetch all related attributes in a single row.</p> <p>What are your thoughts on this design, and what would be your advice to improve it.</p> <p>Thank you for reading.</p>
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      1. USShailesh Kumar
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    1. COLook if using NOSQL databases will help? http://nosql-database.org/
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      1. USAravind R. Yarram
    2. COYou don't need NoSQL to store data in JSON or XML in a field in a database table, and with PostgreSQL you can create functional indexes over specific fields
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    3. COFields in a production database shouldn't be added 'on the fly', there should be some change control to prevent a data mess. Avoid this by doing some up-front design. Add tables as appropriate, or fields to existing tables if the field is 1-1 and it is not too disruptive to change the table.
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