How many taxonomy terms are too many? I have a website where I publish book reviews. For each book I publish 2-3 quotes from the book. I'm using the following fields as taxonomy, so that when a user clicks on them he/she can find more content of that category.


Book name
Author name
Publisher


Lets say, over the period of time, I add reviews of about 5000 books, then there will be 5000 taxonomy terms for "book name". Same for the other categories.

My question is, are these too many taxonomy terms for Drupal? Or is there a better way of doing this. All I'm trying to do is, when a user clicks on author's name, he/she can find more content from that author.
Short answers:


Drupal should have no problem with 5000 terms.
Using a taxonomy for this is the best solution in Drupal. 


You may also want to use Taxonomy manager as suggested by kala4e4k in a comment.

What is the upper limit?

Well, taxonomy vocabularies are managed by the database, so this limit is determined by the maximum number of rows you can store in a table in the database you're using.

If you're using MySQL, there is no built-in limit to the number of rows per table (just pick a big enough number type to manage the primary key), but there are other constraints on table size besides number of rows. If you have a 500 Gbyte hard drive and each record is 1 KB is size, your maximum number of rows will be 500 million (if you dedicate the entire drive to this single table, which is not a very realistic scenario). If you buy a 10 Tbyte hard drive, you may run into your operating systems file size limitation (for instance, I believe Ubuntu's maximum is 5 TB, so your limit will be 5 000 million terms instead of 10 000 milion - given the same assumptions about record size).