非常频繁地拉出很多行 - 我在这里需要memcached吗？

Question

I have about 10 tables with ~10,000 rows each which need to be pulled very often.

For example, list of countries, list of all schools in the world, etc.

PHP can't persist this stuff in memory (to my knowledge) so I would have to query the server for a SELECT * FROM TABLE every time. Should I use memcached here? At first though it's a clear absolutely yes, but at second thought, wouldn't mysql already be caching for me and this would be almost redundant?

I don't have too much understanding of how mysql caches data (or if it even does cache entire tables).

Answer 1

I'd suggest reading up on the MySQL query cache:

http://dev.mysql.com/doc/refman/5.6/en/query-cache.html

Answer 2

You could use MySQL query cache, but then you are still using DB resources to establish the connection and execute the query. Another option is opcode caching if your pages are relatively static. However I think memcached is the most flexible solution. For example if you have a list of countries which need to be accessed from various code-points within your application, you could pull the data from the persistent store (mysql), and store them into memcached. Then the data is available to any part of your application (including batch processes and cronjobs) for any business requirement.

Answer 3

You do need some kind of a cache here, certainly; layers of caching within and surrounding the database are considerably less efficient than what memcached can provide.

That said, if you're jumping to the conclusion that the Right Thing is to cache the query itself, rather than to cache the content you're generating based on the query, I think you're jumping to conclusions -- more analysis is needed.

What data, other than the content of these queries, is used during output generation? Would a page cache or page fragment cache (or caching reverse-proxy in front) make more sense? Is it really necessary to run these queries "often"? How frequently does the underlying data change? Do you have any kind of a notification event when that happens?

Also, SELECT * queries without a WHERE clause are a "code smell" (indicating that something probably is being done the Wrong Way), especially if not all of the data pulled is directly displayed to the user.