This is a general question about mongodb database design, but the reason for my question is that I am designing a database for a system where I generate static html files for a lot of small websites.
The websites can contain different types of pages, some are lists of users, some are lists of other pages and some are just static information pages.
Now I am wondering whether it would be better to have one collection of Pages to store data for all the different kind of website pages or whether it would be better to
have several collections – one collection for each type of page.
If I only use one collection, then this would probably end up with many indexes on a table with many entries, including indexing by type of page.
If a use several collections, then each collection would be smaller and have a few indexes, including one for each collection on the id field.
My gut feeling is that it in general would be better to go with several collections, because then the data is already have one level of indexing by having them in different collections.
But what if the number of different collections is like 100 ?
My question basically is which of the two approaches is preferable with respect to index performance and index size, write performance, locking etc – many collections or one super collection ?
The answer is probably some variant of “it depends”, so which factors are impotant to take into account when deciding which way to go?
The MongoDB documentation discusses this exact issue: http://www.mongodb.org/display/DOCS/Using+a+Large+Number+of+Collections
In general a relatively large number of collections is not an issue.