MongoDB ignores the background option if specified. unique boolean Optional. Creates a unique index so that the collection will not accept insertion or update of documents where the index key value matches an existing value in the index. Specify true to create a unique index. The default value...
CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster] ( name1 [type1] [DEFAULT|MATERIALIZED|ALIAS expr1], name2 [type2] [DEFAULT|MATERIALIZED|ALIAS expr2], ... ) ENGINE = SummingMergeTree([columns]) [PARTITION BY expr] [ORDER BY expr] [SAMPLE BY expr] [SETTINGS name=...
“username” : “mengday2”, “age” : 26, “create_date” : ISODate(“2017-07-30T07:52:43.021Z”) } { “_id” : 3, “username” : “mengday3”, “age” : 26, “create_date” : ISODate(“
In general, using update is better in MongoDB as it will just create the document if it doesn't exist yet, though I'm not sure how to work that with your python adapter. Second, if you only need to know whether or not that document exists, count() which returns only a number will...
createIndex、db.collection.createIndex()、db.collection.createIndexes()命令:创建索引命令 dropIndex、db.collection.dropIndex()、db.collection.dropIndexes()命令:删除索引命令 renameCollection、db.collection.renameCollection()命令:重命名collection命令 reIndex、db.collection.reIndex()命令:删除集合上所有的索引并...
详细信息:https://docs.mongodb.com/manual/core/index-single/ 1.2 复合索引(Compound Index) 针对单复合索引,索引中key的排序顺序决定了索引是否支持排序操作,举例子: 假如:一个对象包含username和date两个属性,如果创建索引如下: db.events.createIndex( { "username" : 1, "date" : -1 } ) ...
I was attempting to write an answer that expanded on my comments and addressed your original ...
db.collectionName.createIndex({创建索引的键:排序规则},{创建索引参数(可选)}) 排序规则: 1表示升序 ,-1表示降序 参数说明: eg.db.collectionName.createIndex({age:1,name:-1},{background:true,name:"indexname"}) 查看索引 db.collectionName.getIndexes() ...
_id属性必须要有,否则在更新数据时会报错:“Element '_id' does not match any field or property of class”。 好,现在看看添加数据的代码怎么写: publicvoidInsert() { //创建数据库链接MongoServer server = MongoDB.Driver.MongoServer.Create(strconn); ...
To create a text or 2d index on a collection that has a non-simple collation, you must explicitly specify {collation: {locale: "simple"} } when creating the index. Collation and Index Use If you have specified a collation at the collection level, then: If you do not specify a collati...