Should I make a composite primary key?

Table links tags with articles. Just a column with ID which usually make the primary key is not really needed. You can make a composite primary key ID tag <-> ID of the article, such a pair will always be unique.

But innodb also stores a copy of the primary key in each table cell, so if it is a composite - it will lead to excessive memory consumption... is it Worth doing or better classic ID and these 2 fields are just unique index the hang?
June 10th 19 at 15:19
2 answers
June 10th 19 at 15:21
But innodb also stores a copy of the primary key in each table cell

And where do you see this? Indexes are stored in a separate structure, and a primary index in InnoDB is a clustered and unique, when the primary - no.
June 10th 19 at 15:23
Got to learn the topic and found it here. Read also.

Find more questions by tags MySQL