Identifying primary key for a vote table

Question

I am working on a voting table design using Postgres 9.5 (but maybe the question itself is applicable to sql in general). My vote table should be like: ------------------------- object | user | timestamp ------------------------- Where object and user are foreign keys to the ids corresponding to their own tables. I have a problem identifying what actually should be a primary key. I thought at first to make a primary_key(object, user) but since I use django as a server, it just doesn't support multicolumn primary key, I am not sure either about the performance since I may access a row using only one of those 2 columns (i.e. object or user), but the advantage this idea works automatically as a unique key since the same user shouldn't vote twice for the same object. And I don't need any additional indexes. The other idea is to introduce an auto or serial id field, I really don't think of any advantage of using this approach especially when the table gets bigger. I need also to introduce at least a unique_key(object, user) which adds to the computational complexity and data storage. Not even sure about the performance when I select using one of the 2 columns, may be I need also 2 additional indexes for the object and user to accelerate the select operation since I need this heavily. Is there something I am missing here? or is there a better idea? JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

django themselves recognise that the "natural primary key" in this case is not supported. So your gut feeling is right, but django don't support it. https://code.djangoproject.com/wiki/MultipleColumnPrimaryKeys Relational database designs use a set of columns as the primary key for a table. When this set includes more than one column, it is known as a “composite” or “compound” primary key. (For more on the terminology, here is an article discussing database keys). Currently Django models only support a single column in this set, denying many designs where the natural primary key of a table is multiple columns. Django currently can't work with these schemas; they must instead introduce a redundant single-column key (a “surrogate” key), forcing applications to make arbitrary and otherwise-unnecessary choices about which key to use for the table in any given instance. I'm less failure with django personally. One option might be to form an extra column as a primary key by concatenating object and user. Remember that there is nothing special about a primary key. You can always add a UNIQUE KEY on the pair of columns and make them both NOT NULL. You might find this example useful. https://thecuriousfrequency.wordpress.com/2014/11/11/make-primary-key-with-two-or-more-field-in-django/