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最新评论
-
davinsam:
import org.mysterylab.utopiafra ...
hibernate dao -
davinsam:
dao类使用说明弄错了,怎么跟basehibernatedao ...
hibernate dao -
like_shadows:
真不错,顶
mongodb基本知识
MongoDB与sql关于库表的名字:
database == database
collection == table
document == row
本篇转载自:http://blog.nosqlfan.com/html/271.html
索引能提高检索数据的速度,你可以想像成在MySQL中创建索引一样,同样索引也是用B-Tree也实现的。
1.单列索引
在字段x上创建索引,1 (表示升序) or -1 (表示降序)
Sql代码
> db.data.ensureIndex({x:1})
显示表data里面的所有索引
Sql代码
> db.data.getIndexes()
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
}
]
查找字段x为6的值,此时已经用到索引了
Sql代码
> db.data.find({x:6})
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
2.默认索引
上述1中db.data.getIndexes()显示出来的一共有2个索引,其中_id是创建表的时候自动创建的索引,此索引是不能够删除的。
3.文档作为索引的键值
a.单列索引
往数据库recommender的表data中插入三条记录
Sql代码
> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});
> db.data.insert({name:"hao123",info:{url:"http://www.hao123.com/",city:"beijing"}});
> db.data.insert({name:"ll4la",info:{url:"http://www.114la.com/",city:"dongguan"}});
对字段info创建索引
Sql代码
> db.data.ensureIndex({info: 1});
显示表data上的所有索引
Sql代码
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
}
]
查找指定的记录,此时会用到索引
Sql代码
> db.data.find({info: {url:"http://www.1616.net/",city:"beijing"}});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
b.组合索引
建立组合索引
Sql代码
> db.data.ensureIndex({"info.url":1, "info.city":1});
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
}
]
下面几个操作均会用到索引
Sql代码
> db.data.find({"info.url": "http://www.1616.net/", "info.city": "beijing"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
> db.data.find({"info.url": "http://www.1616.net/"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
1表示升序(asc),-1表示降序(desc)
Sql代码
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1, "info.city": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": -1});
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
4.组合索引
注意,这里的组合索引与上述3中的b中的组合索引是有点不同的,4里面是对一级字段建立组合索引,而上述3中是对二级字段建立组合索引。
在字段name及info上面创建组合索引
Sql代码
> db.data.ensureIndex({name: 1, info: -1});
MongoDB中索引的用法
作者:nosqlfan on 星期四, 六月 24, 2010 · 1条评论 【阅读:2,024 次】
本文是一篇转载文章,作者在对MongoDB 文档进行了细致的阅读后,总结出了MongoDB的各种索引的用法。
原文链接:http://iamcaihuafeng.blog.sohu.com/151638529.html
索引能提高检索数据的速度,你可以想像成在MySQL中创建索引一样,同样索引也是用B-Tree也实现的。
1.单列索引
在字段x上创建索引,1 (ascending) or -1 (descending)
> db.data.ensureIndex({x:1})
显示表data里面的所有索引
> db.data.getIndexes()
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
}
]
查找字段x为6的值,此时已经用到索引了
> db.data.find({x:6})
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
2.默认索引
上述1中db.data.getIndexes()显示出来的一共有2个索引,其中_id是创建表的时候自动创建的索引,此索引是不能够删除的。
An index is always created on _id. This index is special and cannot be deleted. The _id index enforces uniqueness for its keys.
3.文档作为索引的键值
a.单列索引
MongoDB的官方文档上面是这样说的:
Documents as Keys
Indexed fields may be of any type, including documents:
往数据库recommender的表data中插入三条记录
> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});
> db.data.insert({name:"hao123",info:{url:"http://www.hao123.com/",city:"beijing"}});
> db.data.insert({name:"ll4la",info:{url:"http://www.114la.com/",city:"dongguan"}});
对字段info创建索引
> db.data.ensureIndex({info: 1});
显示表data上的所有索引
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
}
]
查找指定的记录,此时会用到索引
> db.data.find({info: {url:"http://www.1616.net/",city:"beijing"}});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
b.组合索引
建立组合索引
> db.data.ensureIndex({"info.url":1, "info.city":1});
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
}
]
下面几个操作均会用到索引
> db.data.find({"info.url": "http://www.1616.net/", "info.city": "beijing"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
> db.data.find({"info.url": "http://www.1616.net/"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
1表示升序(asc),-1表示降序(desc)
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1, "info.city": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": -1});
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114 la.com/", "city" : "dongguan" } }
4.组合索引
注意,这里的组合索引与上述3中的b中的组合索引是有点不同的,4里面是对一级字段建立组合索引,而上述3中是对二级字段建立组合索引。
在字段name及info上面创建组合索引
> db.data.ensureIndex({name: 1, info: -1});
显示所有的索引
Sql代码
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
},
{
"_id" : ObjectId("4befbfcfb0e29ba1ce20e0c1"),
"ns" : "recommender.data",
"key" : {
"name" : 1,
"info" : -1
},
"name" : "name_1_info_-1"
}
]
下面的排序将用到上面的索引
Sql代码
> db.data.find({"info.url": /http:*/i}).sort({name:1, info: -1});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
5.唯一索引
往表data中插入一条记录。
Sql代码
> db.data.insert({firstname: "cai", lastname: "huafeng"});
由于表data中只有一记录有字段firstname及lastname,其它的行均没有相应的值,也就是均为null,为null就说明是相同的,而唯一索引是不允许有相同的值的,所以下面创建唯一组合索引时报错了。
所以建立唯一索引时,不管是对单个字段还是多个字段建立索引,则最好每一行均有此字段,否则会报错。
Sql代码
> db.data.find();
{ "_id" : ObjectId("4bee745a0863b1c233b8b7ea"), "name" : "caihuafeng" }
{ "_id" : ObjectId("4bee745f0863b1c233b8b7eb"), "website" : "1616.net" }
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befc51ab0e29ba1ce20e0c2"), "firstname" : "cai", "lastname" : "huafeng" }
> db.data.ensureIndex({firstname: 1, lastname: 1}, {unique: true});
E11000 duplicate key error index: recommender.data.$firstname_1_lastname_1 dup key: { : null, : null }
6.删除索引
a.删除某个表中的所有索引
Sql代码
db.collection.dropIndexes();
b.删除某个表中的单一索引
Sql代码
db.collection.dropIndex({x: 1, y: -1})
> db.data.dropIndex({firstname: 1, lastname: 1});
{ "nIndexesWas" : 6, "ok" : 1 }
database == database
collection == table
document == row
本篇转载自:http://blog.nosqlfan.com/html/271.html
索引能提高检索数据的速度,你可以想像成在MySQL中创建索引一样,同样索引也是用B-Tree也实现的。
1.单列索引
在字段x上创建索引,1 (表示升序) or -1 (表示降序)
Sql代码
> db.data.ensureIndex({x:1})
显示表data里面的所有索引
Sql代码
> db.data.getIndexes()
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
}
]
查找字段x为6的值,此时已经用到索引了
Sql代码
> db.data.find({x:6})
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
2.默认索引
上述1中db.data.getIndexes()显示出来的一共有2个索引,其中_id是创建表的时候自动创建的索引,此索引是不能够删除的。
3.文档作为索引的键值
a.单列索引
往数据库recommender的表data中插入三条记录
Sql代码
> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});
> db.data.insert({name:"hao123",info:{url:"http://www.hao123.com/",city:"beijing"}});
> db.data.insert({name:"ll4la",info:{url:"http://www.114la.com/",city:"dongguan"}});
对字段info创建索引
Sql代码
> db.data.ensureIndex({info: 1});
显示表data上的所有索引
Sql代码
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
}
]
查找指定的记录,此时会用到索引
Sql代码
> db.data.find({info: {url:"http://www.1616.net/",city:"beijing"}});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
b.组合索引
建立组合索引
Sql代码
> db.data.ensureIndex({"info.url":1, "info.city":1});
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
}
]
下面几个操作均会用到索引
Sql代码
> db.data.find({"info.url": "http://www.1616.net/", "info.city": "beijing"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
> db.data.find({"info.url": "http://www.1616.net/"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
1表示升序(asc),-1表示降序(desc)
Sql代码
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1, "info.city": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": -1});
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
4.组合索引
注意,这里的组合索引与上述3中的b中的组合索引是有点不同的,4里面是对一级字段建立组合索引,而上述3中是对二级字段建立组合索引。
在字段name及info上面创建组合索引
Sql代码
> db.data.ensureIndex({name: 1, info: -1});
MongoDB中索引的用法
作者:nosqlfan on 星期四, 六月 24, 2010 · 1条评论 【阅读:2,024 次】
本文是一篇转载文章,作者在对MongoDB 文档进行了细致的阅读后,总结出了MongoDB的各种索引的用法。
原文链接:http://iamcaihuafeng.blog.sohu.com/151638529.html
索引能提高检索数据的速度,你可以想像成在MySQL中创建索引一样,同样索引也是用B-Tree也实现的。
1.单列索引
在字段x上创建索引,1 (ascending) or -1 (descending)
> db.data.ensureIndex({x:1})
显示表data里面的所有索引
> db.data.getIndexes()
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
}
]
查找字段x为6的值,此时已经用到索引了
> db.data.find({x:6})
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
2.默认索引
上述1中db.data.getIndexes()显示出来的一共有2个索引,其中_id是创建表的时候自动创建的索引,此索引是不能够删除的。
An index is always created on _id. This index is special and cannot be deleted. The _id index enforces uniqueness for its keys.
3.文档作为索引的键值
a.单列索引
MongoDB的官方文档上面是这样说的:
Documents as Keys
Indexed fields may be of any type, including documents:
往数据库recommender的表data中插入三条记录
> db.data.insert({name:"1616",info:{url:"http://www.1616.net/",city:"beijing"}});
> db.data.insert({name:"hao123",info:{url:"http://www.hao123.com/",city:"beijing"}});
> db.data.insert({name:"ll4la",info:{url:"http://www.114la.com/",city:"dongguan"}});
对字段info创建索引
> db.data.ensureIndex({info: 1});
显示表data上的所有索引
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
}
]
查找指定的记录,此时会用到索引
> db.data.find({info: {url:"http://www.1616.net/",city:"beijing"}});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
b.组合索引
建立组合索引
> db.data.ensureIndex({"info.url":1, "info.city":1});
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
}
]
下面几个操作均会用到索引
> db.data.find({"info.url": "http://www.1616.net/", "info.city": "beijing"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
> db.data.find({"info.url": "http://www.1616.net/"});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
1表示升序(asc),-1表示降序(desc)
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1, "info.city": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": 1});
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
> db.data.find({"info.url": /http:*/i}).sort({"info.url": -1});
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114 la.com/", "city" : "dongguan" } }
4.组合索引
注意,这里的组合索引与上述3中的b中的组合索引是有点不同的,4里面是对一级字段建立组合索引,而上述3中是对二级字段建立组合索引。
在字段name及info上面创建组合索引
> db.data.ensureIndex({name: 1, info: -1});
显示所有的索引
Sql代码
> db.data.getIndexes();
[
{
"name" : "_id_",
"ns" : "recommender.data",
"key" : {
"_id" : 1
}
},
{
"_id" : ObjectId("4befb146b0e29ba1ce20e0bb"),
"ns" : "recommender.data",
"key" : {
"x" : 1
},
"name" : "x_1"
},
{
"_id" : ObjectId("4befb76bb0e29ba1ce20e0bf"),
"ns" : "recommender.data",
"key" : {
"info" : 1
},
"name" : "info_1"
},
{
"_id" : ObjectId("4befb9d1b0e29ba1ce20e0c0"),
"ns" : "recommender.data",
"key" : {
"info.url" : 1,
"info.city" : 1
},
"name" : "info.url_1_info.city_1"
},
{
"_id" : ObjectId("4befbfcfb0e29ba1ce20e0c1"),
"ns" : "recommender.data",
"key" : {
"name" : 1,
"info" : -1
},
"name" : "name_1_info_-1"
}
]
下面的排序将用到上面的索引
Sql代码
> db.data.find({"info.url": /http:*/i}).sort({name:1, info: -1});
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
5.唯一索引
往表data中插入一条记录。
Sql代码
> db.data.insert({firstname: "cai", lastname: "huafeng"});
由于表data中只有一记录有字段firstname及lastname,其它的行均没有相应的值,也就是均为null,为null就说明是相同的,而唯一索引是不允许有相同的值的,所以下面创建唯一组合索引时报错了。
所以建立唯一索引时,不管是对单个字段还是多个字段建立索引,则最好每一行均有此字段,否则会报错。
Sql代码
> db.data.find();
{ "_id" : ObjectId("4bee745a0863b1c233b8b7ea"), "name" : "caihuafeng" }
{ "_id" : ObjectId("4bee745f0863b1c233b8b7eb"), "website" : "1616.net" }
{ "_id" : ObjectId("4bee804ba23d558eb6687117"), "x" : 6, "name" : "caihuafeng1" }
{ "_id" : ObjectId("4bee804ba23d558eb6687118"), "x" : 6, "name" : "caihuafeng2" }
{ "_id" : ObjectId("4bee804ba23d558eb6687119"), "x" : 6, "name" : "caihuafeng3" }
{ "_id" : ObjectId("4bee804ba23d558eb668711a"), "x" : 6, "name" : "caihuafeng4" }
{ "_id" : ObjectId("4bee804ba23d558eb668711b"), "x" : 6, "name" : "caihuafeng5" }
{ "_id" : ObjectId("4bee804ba23d558eb668711c"), "x" : 6, "name" : "caihuafeng6" }
{ "_id" : ObjectId("4bee804ba23d558eb668711d"), "x" : 6, "name" : "caihuafeng7" }
{ "_id" : ObjectId("4bee804ba23d558eb668711e"), "x" : 6, "name" : "caihuafeng8" }
{ "_id" : ObjectId("4bee804ba23d558eb668711f"), "x" : 6, "name" : "caihuafeng9" }
{ "_id" : ObjectId("4bee804ba23d558eb6687120"), "x" : 6, "name" : "caihuafeng10" }
{ "_id" : ObjectId("4befb711b0e29ba1ce20e0bc"), "name" : "1616", "info" : { "url" : "http://www.1616.net/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb723b0e29ba1ce20e0bd"), "name" : "hao123", "info" : { "url" : "http://www.hao123.com/", "city" : "beijing" } }
{ "_id" : ObjectId("4befb740b0e29ba1ce20e0be"), "name" : "ll4la", "info" : { "url" : "http://www.114la.com/", "city" : "dongguan" } }
{ "_id" : ObjectId("4befc51ab0e29ba1ce20e0c2"), "firstname" : "cai", "lastname" : "huafeng" }
> db.data.ensureIndex({firstname: 1, lastname: 1}, {unique: true});
E11000 duplicate key error index: recommender.data.$firstname_1_lastname_1 dup key: { : null, : null }
6.删除索引
a.删除某个表中的所有索引
Sql代码
db.collection.dropIndexes();
b.删除某个表中的单一索引
Sql代码
db.collection.dropIndex({x: 1, y: -1})
> db.data.dropIndex({firstname: 1, lastname: 1});
{ "nIndexesWas" : 6, "ok" : 1 }
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MongoDB索引是数据库性能优化的关键工具,它们类似于书籍的目录,可以帮助快速定位到所需的数据,从而大大提高查询效率。在没有索引的情况下,MongoDB必须遍历整个集合来找到匹配的文档,这在数据量大的时候会导致...
#### MongoDB索引 - **介绍**:索引能够显著提高查询性能,MongoDB支持单字段索引、复合索引、唯一索引等多种类型的索引。 - **后台创建索引**:可以在运行时创建索引,而无需停止服务。 - **索引类型**: - **单...
MongoDB 数据库索引介绍 MongoDB 数据库索引是提高查询性能和减少查询时间的重要手段。索引可以告诉 MongoDB 如何高效地检索数据,以便快速地找到所需的数据。在本文中,我们将深入探讨 MongoDB 数据库索引的基础...
MongoDB的索引是数据库性能优化的关键因素,与MySQL、Oracle等关系型数据库中的索引原理相似,但具有自身的特性和限制。MongoDB的索引建立在Collection(表)级别,采用B-树数据结构来加速查询和排序操作。 1. 默认...
本篇文章将详细探讨MongoDB中的索引管理以及高级索引概念。 1. **查看索引** MongoDB 提供了两种方法来查看集合上的索引。`db.COLLECTION_NAME.getIndexes()` 方法返回集合上所有索引的详细信息,而 `db.system....
索引是 MongoDB 中的关键概念,它们能够显著提升查询性能。本篇资料主要涵盖了 MongoDB 的索引使用和查询分析,以下是对这些知识点的详细解释: 1. **explain操作**:`explain` 是 MongoDB 提供的一个命令,用于...
在 MongoDB 中,索引的创建对于优化查询效率至关重要。以下是关于MongoDB创建索引的一些详细知识点: 1. **创建索引的方法**: MongoDB 使用 `ensureIndex()` 方法来创建索引。尽管在较新的版本中,`createIndex()...
索引是提升查询性能的关键工具,本文将详细介绍MongoDB中的索引基础知识、唯一索引、索引参数以及如何通过`explain`分析查询速度。 一、索引基础 在MongoDB中,索引是一种特殊的数据结构,它们对集合中的一列或多...
MongoDB是一个基于文档的NoSQL数据库,由C++语言编写,旨在为大量分布式数据提供高性能、高可用...6. **索引**:支持多种类型的索引,以优化查询性能。 7. **灵活的聚合框架**:MongoDB的聚合框架允许用户执行复杂的数
在MongoDB中,索引扮演着至关重要的角色,它类似于传统的关系型数据库,通过B-Tree数据结构加速数据查找和排序。 ### 一、索引简介 MongoDB 的索引可以通过`ensureIndex()`函数创建,指定一个或多个字段来提升查询...
MongoDB数据库
1. 普通索引 1. 单列索引 2. 多列索引 3. 子文档索引 2. 唯一索引 3. 稀疏索引 4. 哈希索引 5. 重建索引 6. 删除索引 7. 查看索引