1.2 KiB
1.2 KiB
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Database caching, what to cache
Introduction
There are multiple levels you can cache that fall into two general categories: database queries and objects:
- Row level
- Query-level
- Fully-formed serializable objects
- Fully-rendered HTML
Generaly, you should try to avoid file-based caching, as it makes cloning and auto-scaling more difficult.
Caching at the database query level
Whenever you query the database, hash the query as a key and store the result to the cache. This approach suffers from expiration issues:
- Hard to delete a cached result with complex queries
- If one piece of data changes such as a table cell, you need to delete all cached queries that might include the changed cell
Caching at the object level
See your data as an object, similar to what you do with your application code. Have your application assemble the dataset from the database into a class instance or a data structure(s) :
- Remove the object from cache if its underlying data has changed
- Allows for asynchronous processing: workers assemble objects by consuming the latest cached object
Suggestions of what to cache:
- User sessions
- Fully rendered web pages
- Activity streams
- User graph data