show collections system.ind..."/>
您好,登錄后才能下訂單哦!
使用ensureIndex函數(shù)創(chuàng)建集合的索引。
對(duì)集合而言,每個(gè)索引只需要?jiǎng)?chuàng)建一次,重復(fù)創(chuàng)建沒有任何作用;
> show collections system.indexes users
所有的數(shù)據(jù)庫(kù)的索引元數(shù)據(jù)都存放在system.indexs的集合中;
使用getIndexes函數(shù)查看給定的集合上的索引信息:
> db.users.getIndexes() [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "blog.users" }, { "v" : 1, "key" : { "username" : 1 }, "name" : "username_1", "ns" : "blog.users" }, { "v" : 1, "key" : { "age" : 1, "username" : 1 }, "name" : "age_1_username_1", "ns" : "blog.users" } ] >
可以適應(yīng)dropIndex函數(shù)刪除指定的索引:
> db.users.dropIndex({"username":1}) { "nIndexesWas" : 3, "ok" : 1 } > db.users.getIndexes() [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "blog.users" }, { "v" : 1, "key" : { "age" : 1, "username" : 1 }, "name" : "age_1_username_1", "ns" : "blog.users" } ] >
上述的例子中可以看到索引的標(biāo)識(shí)默認(rèn)格式為keyname1_dir1_keyname2_dir….keynameN_DirN;
也可以指定標(biāo)識(shí)名:
> db.users.ensureIndex({"username":1},{"name":"firstname"}) { "createdCollectionAutomatically" : false, "numIndexesBefore" : 2, "numIndexesAfter" : 3, "ok" : 1 } > db.users.getIndexes() [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "blog.users" }, { "v" : 1, "key" : { "age" : 1, "username" : 1 }, "name" : "age_1_username_1", "ns" : "blog.users" }, { "v" : 1, "key" : { "username" : 1 }, "name" : "firstname", "ns" : "blog.users" } ] >
修改索引的步驟:刪除索引—>創(chuàng)建索引;
刪除索引可以直接指定索引標(biāo)識(shí),例如:
> db.users.dropIndex("firstname") { "nIndexesWas" : 3, "ok" : 1 } > db.users.getIndexes() [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "blog.users" }, { "v" : 1, "key" : { "age" : 1, "username" : 1 }, "name" : "age_1_username_1", "ns" : "blog.users" } ] >
免責(zé)聲明:本站發(fā)布的內(nèi)容(圖片、視頻和文字)以原創(chuàng)、轉(zhuǎn)載和分享為主,文章觀點(diǎn)不代表本網(wǎng)站立場(chǎng),如果涉及侵權(quán)請(qǐng)聯(lián)系站長(zhǎng)郵箱:is@yisu.com進(jìn)行舉報(bào),并提供相關(guān)證據(jù),一經(jīng)查實(shí),將立刻刪除涉嫌侵權(quán)內(nèi)容。