Universal Table/Join Table A Good Idea?

Question

Let's say you have a list of entities: Post, Question, and Gallery and these entities can be liked and commented on by a user and also hold tags.

Would would it be a good idea to compact things so there's not a bunch of tables (Option 1) or is it better to create as many tables as necessary although the tables will look very similar to each other (Option 2).

Option 1

• Create a universal like_, comment, and tag TABLE which holds the 'entity_type' so you know which entity the like belongs to and an entity TABLE to ensure data integrity. A good thing about this option is I could add more entities and only have to create 1 table per entity vs 4 (one for the entity, a like join table, a comment join table, a tag join table):

enitity

• entity_id PRIMARY KEY

entity_type

• en_type TEXT PRIMARY KEY
• description

post

• post_id PRIMARY KEY
• post_id REFERENCES entity(entity_id);

gallery

• gallery_id PRIMARY KEY
• gallery_id REFERENCES entity(entity_id)

question

• question_id PRIMARY KEY
• question_id REFERENCES entity(entity_id)

tag

• tag_id
• tag_name

like_

• entity_type
• entity_id
• user_id
• entity_type REFERENCES entity_type(en_type)
• entity_id REFERENCES entity(entity_id);

comment

• entity_type
• entity_id
• user_id
• comm
• entity_type REFERENCES entity_type(en_type)
• entity_id REFERENCES entity(entity_id);

tag_to_entity

• entity_type
• entity_id
• tag_id

Option 2

• Separate everything. Here everything is straight forward but there's a lot more tables.

tag

• tag_id
• tag_name

post

• post_id PRIMARY KEY

gallery

• gallery_id PRIMARY KEY

question

• question_id PRIMARY KEY

like_to_post

• post_id
• user_id
• post_id REFERENCES post(post_id)

like_to_gallery

• gallery_id
• user_id
• gallery_id REFERENCES gallery(gallery_id)

like_to_gallery

• question_id
• user_id
• question_id REFERENCES question(question_id)

comment_to_post

• post_id
• user_id
• comment_text
• post_id REFERENCES post(post_id)

comment_to_gallery

• gallery_id
• user_id
• comment_text
• gallery_id REFERENCES gallery(gallery_id)

comment_to_question

• question_id
• user_id
• comment_text
• gallery_id REFERENCES question(question_id)

tag_to_post

• post_id
• tag_id
• post_id REFERENCES post(post_id)

tag_to_gallery

• gallery_id
• tag_id
• gallery_id REFERENCES gallery(gallery_id)

tag_to_question

• question_id
• tag_id
• question_id REFERENCES question(question_id)

Answer 1

I would say option 2 is preferable because:

1. It allows the database to enforce foreign key constraints on you join tables
2. Performance will likely be better because the size of your joins will be much smaller