nosql

问题 I'm trying to run a query on a dynamoDB table with the key condition as such KeyConditions: { userID: { ComparisonOperator: 'GE', AttributeValueList: [{N: '0'}] } } When I run this query with the ComparisonOperator as 'EQ' no problems occur. However when it's 'GE' I get an error stating that the query key condition is not supported. Note that userID is a hash key 回答1: From the Dynamo DB Query Documentation: A Query operation directly accesses items from a table using the table primary key, or

问题 I'm trying to run a query on a dynamoDB table with the key condition as such KeyConditions: { userID: { ComparisonOperator: 'GE', AttributeValueList: [{N: '0'}] } } When I run this query with the ComparisonOperator as 'EQ' no problems occur. However when it's 'GE' I get an error stating that the query key condition is not supported. Note that userID is a hash key 回答1: From the Dynamo DB Query Documentation: A Query operation directly accesses items from a table using the table primary key, or

问题 I am new to graph database, and overwhelmed with its promised scope and power. When designing app, it is very important that we align our emotional design patterns with practical performance designs. One of the question that is bothering me is whether to make certain piece of information as relation attribute or node attribute. Here's the use case. We have entities that are related by incoming relation "service_provider". The starting node becomes a provider to end node. Now each of the

问题 I am working with Azure DocumentDB. I am looking at the ExecuteNextAsync operation. What I am seeing is the the ExecuteNextAsync returns no resluts. I am using examples I have found on line and don't generate any results. If I call an enumeration operation on the initial query results are returned. Is there an example showing the complete configuration for using ExecuteNextAsync? Update To be more explicit I am not actually getting any results. The call seems to just run and no error is

问题 When i use System.linq to query objects in a MongoCollection: var result = collection.Find(query).Where(x => x.something == something); is this a query done on the database or on the collection in memory? for instance "SetSkip" creates the query in MongoDb but "Skip" does it in memory. If ".Where" is done in memory is there a way not to do this? 回答1: The .Where query is done in memory via IEnumerable.Where because it's performed on the result of the Find call that establishes the MongoDB

问题 I am following their tutorial here: http://developers.sones.de/wiki/doku.php?id=quickreference:fiveminuteguide But when I copy and paste this command in webshell CREATE VERTICES ABSTRACT Entity ATTRIBUTES (String Name), University EXTENDS Entity ATTRIBUTES(SET<Student> Students), City EXTENDS Entity ATTRIBUTES(SET<University> Universities), Student EXTENDS Entity ATTRIBUTES(Integer Age) BACKWARDEDGES(University.Students StudiesAt) The output generates error: GraphDB@localhost [gql-mode] >

问题 I am developing a web system to handle a very large set of small images, about 100 millions images of 50kb ~ 200kb, working on ReiserFS . For now, it is very difficult to backup and sync those large number of small files. My question is that if it a good idea to store these small images to a key/value store or other nosql database such as GridFS (Mongodb) , Tokyo Tyrant , Voldemort to gain more performance and bring better backup support? 回答1: First off, have a look at this: Storing a millon

问题 I'm on a project working with data of a bike-sharing service. Each trip has the following info > db.bikes.find({bike:9990}).pretty() { "_id" : ObjectId("5bb59fd8e9fb374bf0cd5c1c"), "gender" : "M", "userAge" : 49, "bike" : 9990, "depStation" : 150, "depDate" : "01/08/2018", "depHour" : "0:00:13", "arrvStation" : 179, "arrvDate" : "01/08/2018", "arrvHour" : "0:23:38" } How do I group for each hour of the day and count the number of trips made in that specific hour? I'm trying with this query db

问题 Following is my code : error_log('before query'.date("H:i:s:ms")); $response = $client->query(array( "TableName" => "user", "KeyConditions" => array( "userId" => array( "ComparisonOperator" => ComparisonOperator::EQ, "AttributeValueList" => array( array(Type::NUMBER => 2) ))), )); error_log('after query'.date("H:i:s:ms")); print_r($response); My tables Read capacity is 6 reads/sec Output of Error logs before query 16:05:29:0229 after query 16:05:32:0232 Question: Why it took 3 secs to read

问题 I am trying to come up with a partition key strategy based on a DateTime that doesn't result in the Append-Only write bottleneck often described in best practices guidelines. Basically, if you partition by something like YYYY-MM-DD, all your writes for a particular day will end up the same partition, which will reduce write performance. Ideally, a partition key should even distribute writes across as many partitions as possible. To accomplish this while still basing the key off a DateTime