问题：
我们有一个社交网站，成员可以互相评价兼容性或匹配性。该user_match_ratings表包含超过2.2亿行（9 gig数据或近20 gig索引）。对该表的查询通常显示在slow.log（阈值> 2秒）中，并且是系统中最常记录的慢速查询：
Query_time: 3 Lock_time: 0 Rows_sent: 3 Rows_examined: 1051
"select rating, count(*) as tally from user_match_ratings where rated_user_id = 395357 group by rating;"
Query_time: 4 Lock_time: 0 Rows_sent: 3 Rows_examined: 1294
"select rating, count(*) as tally from user_match_ratings where rated_user_id = 4182969 group by rating;"
Query_time: 3 Lock_time: 0 Rows_sent: 3 Rows_examined: 446
"select rating, count(*) as tally from user_match_ratings where rated_user_id = 630148 group by rating;"
Query_time: 5 Lock_time: 0 Rows_sent: 3 Rows_examined: 3788
"select rating, count(*) as tally from user_match_ratings where rated_user_id = 1835698 group by rating;"
Query_time: 17 Lock_time: 0 Rows_sent: 3 Rows_examined: 4311
"select rating, count(*) as tally from user_match_ratings where rated_user_id = 1269322 group by rating;"MySQL版本：
- 协议版本：10
- 版本：5.0.77-log
- 版本bdb：Sleepycat软件：Berkeley DB 4.1.24：（2009年1月29日）
- 版本编译机：x86_64 version_compile_os：redhat-linux-gnu
表信息：
SHOW COLUMNS FROM user_match_ratings;给出：
╔═══════════════╦════════════╦════╦═════╦════════╦════════════════╗
║ id ║ int(11) ║ NO ║ PRI ║ NULL ║ auto_increment ║
║ rater_user_id ║ int(11) ║ NO ║ MUL ║ NULL ║ ║
║ rated_user_id ║ int(11) ║ NO ║ MUL ║ NULL ║ ║
║ rating ║ varchar(1) ║ NO ║ ║ NULL ║ ║
║ created_at ║ datetime ║ NO ║ ║ NULL ║ ║
╚═══════════════╩════════════╩════╩═════╩════════╩════════════════╝查询样例：
select * from mutual_match_ratings where id=221673540;给出：
╔═══════════╦═══════════════╦═══════════════╦════════╦══════════════════════╗
║ id ║ rater_user_id ║ rated_user_id ║ rating ║ created_at ║
╠═══════════╬═══════════════╬═══════════════╬════════╬══════════════════════╣
║ 221673540 ║ 5699713 ║ 3890950 ║ N ║ 2013-04-09 13:00:38 ║
╚═══════════╩═══════════════╩═══════════════╩════════╩══════════════════════╝指标
该表设置了3个索引：
- 单一索引
rated_user_id - 关于综合指数
rater_user_id和created_at - 关于综合指数
rated_user_id和rater_user_id
显示来自user_match_ratings的索引；
给出：
╔════════════════════╦════════════╦═══════════════════════════╦══════════════╦═══════════════╦═══════════╦═════════════╦══════════╦════════╦═════════════════════════╦════════════╦══════════════════╗
║ Table ║ Non_unique ║ Key_name ║ Seq_in_index ║ Column_name ║ Collation ║ Cardinality ║ Sub_part ║ Packed ║ Null ║ Index_type ║ Comment ║
╠════════════════════╬════════════╬═══════════════════════════╬══════════════╬═══════════════╬═══════════╬═════════════╬══════════╬════════╬═════════════════════════╬════════════╬══════════════════╣
║ user_match_ratings ║ 0 ║ PRIMARY ║ 1 ║ id ║ A ║ 220781193 ║ NULL ║ NULL ║ BTREE ║ ║ ║
║ user_match_ratings ║ 1 ║ user_match_ratings_index1 ║ 1 ║ rater_user_id ║ A ║ 11039059 ║ NULL ║ NULL ║ BTREE ║ ║ ║
║ user_match_ratings ║ 1 ║ user_match_ratings_index1 ║ 2 ║ created_at ║ A ║ 220781193 ║ NULL ║ NULL ║ BTREE ║ ║ ║
║ user_match_ratings ║ 1 ║ user_match_ratings_index2 ║ 1 ║ rated_user_id ║ A ║ 4014203 ║ NULL ║ NULL ║ BTREE ║ ║ ║
║ user_match_ratings ║ 1 ║ user_match_ratings_index2 ║ 2 ║ rater_user_id ║ A ║ 220781193 ║ NULL ║ NULL ║ BTREE ║ ║ ║
║ user_match_ratings ║ 1 ║ user_match_ratings_index3 ║ 1 ║ rated_user_id ║ A ║ 2480687 ║ NULL ║ NULL ║ BTREE ║ ║ ║
╚════════════════════╩════════════╩═══════════════════════════╩══════════════╩═══════════════╩═══════════╩═════════════╩══════════╩════════╩═════════════════════════╩════════════╩══════════════════╝即使使用索引，这些查询也很慢。
我的问题：
将此表/数据分离到服务器上具有足够内存以将这些数据存储在内存中的另一个数据库上，是否会加快这些查询的速度？无论如何，表/索引是否有任何设置可以改进以使这些查询更快？
目前，我们有16GB的内存；但是，我们正在考虑将现有计算机升级到32GB或添加至少具有那么多（可能还有固态驱动器）的新计算机。
查看要查询的表上的索引。通常，通过创建适当的索引可以对查询进行很多改进。并非总是如此，但是在很多情况下，可以通过对查询的where子句中的列提供索引来快速进行查询。特别是当桌子越来越大时。
—
Ranknoodle
当然@Ranknoodle。谢谢。我会分别检查。
—
NullPointer
SELECT QUERY。你能建议吗？PS您的问题迫使我加入了这个社区（y）;）