Can i add condition where i will say if attribute one is equal to attribute two then return it in the result or what will be a logic in the application level to do this?
I need somehow this filtering and pagination which i'm going to use lastKey bla bla ...
I don't know if dynamodb using java sdk or any other sdk support this to compare two attributes to retrieve data.
QueryRequest queryRequest = new QueryRequest()
.withTableName(tableName)
.withIndexName(indexName)
.withLimit(maxResult)
.withExclusiveStartKey(exclusiveStartKey)
.withKeyConditions(keyConditions)
.withScanIndexForward(false);
if(attributesToget == null) {
queryRequest = queryRequest.withSelect(Select.ALL_ATTRIBUTES);
} else {
queryRequest = queryRequest.withSelect(Select.SPECIFIC_ATTRIBUTES)
.withAttributesToGet(attributesToget);
}
return queryRequest;
Related
I have following Code where i will receive list of names as parameter.In the loop, first i'm assigning index 0 value from list to local variable name. There after comparing next values from list with name. If we receive any non-equal value from list, i'm assigning value of result as 1 and failing the test case.
Below is the Array list
List<String> names= new ArrayList<String>();
names.add("John");
names.add("Mark");
Below is my selenium test method
public void test(List<String> names)
String name=null;
int a=0;
for(String value:names){
if(name==null){
System.out.println("Value is null");
name=value;
}
else if(name.equals(value)){
System.out.println("Received Same name");
name=value;
}
else{
a=1;
Assert.fail("Received different name in between");
}
}
How can i convert above code into lambda expressions?. I'm using cucumber data model, hence i receive data as list from feature file. Since i can't give clear explanation, just posted the example logic i need to convert to lambda expression.
Here's the solution: it cycles all element in your list checking if are all the same.
You can try adding or editing the list so you can have different outputs. I've written the logic, you can easly put it into a JUnit test
List<String> names= new ArrayList<>();
names.add("John");
names.add("Mark");
String firstEntry = names.get(0);
boolean allMatch = names.stream().allMatch(name -> firstEntry.equals(name));
System.out.println("All names are the same: "+allMatch);
Are you looking for duplicates, whenever you have distinct value , set a=1 and say assert to fail. You can achieve this by :
List<String> names= new ArrayList<String>();
names.add("John");
names.add("Mark");
if (names.stream().distinct().limit(2).count() > 1) {
a= 1,
Assert.fail("Received different name in between");
} else {
System.out.println("Received Same name");
}
I am storing some filter data in my table. Let me make it more clear: I want to store some where clauses and their values in a database and use them when I want to retrieve data from a database.
For example, consider a people table (entity set) and some filters on it in another table:
"age" , "> 70"
"gender" , "= male"
Now when I retrieve data from the people table I want to get these filters to filter my data.
I know I can generate a SQL query as a string and execute that but is there any other better way in EF, LINQ?
One solution is to use Dynamic Linq Library , using this library you can have:
filterTable = //some code to retrive it
var whereClause = string.Join(" AND ", filterTable.Select(x=> x.Left + x.Right));
var result = context.People.Where(whereClause).ToList();
Assuming that filter table has columns Left and Right and you want to join filters by AND.
My suggestion is to include more details in the filter table, for example separate the operators from operands and add a column that determines the join is And or OR and a column that determines the other row which joins this one. You need a tree structure if you want to handle more complex queries like (A and B)Or(C and D).
Another solution is to build expression tree from filter table. Here is a simple example:
var arg = Expression.Parameter(typeof(People));
Expression whereClause;
for(var row in filterTable)
{
Expression rowClause;
var left = Expression.PropertyOrField(arg, row.PropertyName);
//here a type cast is needed for example
//var right = Expression.Constant(int.Parse(row.Right));
var right = Expression.Constant(row.Right, left.Member.MemberType);
switch(row.Operator)
{
case "=":
rowClause = Expression.Equal(left, right);
break;
case ">":
rowClause = Expression.GreaterThan(left, right);
break;
case ">=":
rowClause = Expression.GreaterThanOrEqual(left, right);
break;
}
if(whereClause == null)
{
whereClause = rowClause;
}
else
{
whereClause = Expression.AndAlso(whereClause, rowClause);
}
}
var lambda = Expression.Lambda<Func<People, bool>>(whereClause, arg);
context.People.Where(lambda);
this is very simplified example, you should do many validations type casting and ... in order to make this works for all kind of queries.
This is an interesting question. First off, make sure you're honest with yourself: you are creating a new query language, and this is not a trivial task (however trivial your expressions may seem).
If you're certain you're not underestimating the task, then you'll want to look at LINQ expression trees (reference documentation).
Unfortunately, it's quite a broad subject, I encourage you to learn the basics and ask more specific questions as they come up. Your goal is to interpret your filter expression records (fetched from your table) and create a LINQ expression tree for the predicate that they represent. You can then pass the tree to Where() calls as usual.
Without knowing what your UI looks like here is a simple example of what I was talking about in my comments regarding Serialize.Linq library
public void QuerySerializeDeserialize()
{
var exp = "(User.Age > 7 AND User.FirstName == \"Daniel\") OR User.Age < 10";
var user = Expression.Parameter(typeof (User), "User");
var parsExpression =
System.Linq.Dynamic.DynamicExpression.ParseLambda(new[] {user}, null, exp);
//Convert the Expression to JSON
var query = e.ToJson();
//Deserialize JSON back to expression
var serializer = new ExpressionSerializer(new JsonSerializer());
var dExp = serializer.DeserializeText(query);
using (var context = new AppContext())
{
var set = context.Set<User>().Where((Expression<Func<User, bool>>) dExp);
}
}
You can probably get fancier using reflection and invoking your generic LINQ query based on the types coming in from the expression. This way you can avoid casting the expression like I did at the end of the example.
So I have a standard service reference proxy calss for MS CRM 2013 (i.e. right-click add reference etc...) I then found the limitation that CRM data calls limit to 50 results and I wanted to get the full list of results. I found two methods, one looks more correct, but doesn't seem to work. I was wondering why it didn't and/or if there was something I'm doing incorrectly.
Basic setup and process
crmService = new CrmServiceReference.MyContext(new Uri(crmWebServicesUrl));
crmService.Credentials = System.Net.CredentialCache.DefaultCredentials;
var accountAnnotations = crmService.AccountSet.Where(a => a.AccountNumber = accountNumber).Select(a => a.Account_Annotation).FirstOrDefault();
Using Continuation (something I want to work, but looks like it doesn't)
while (accountAnnotations.Continuation != null)
{
accountAnnotations.Load(crmService.Execute<Annotation>(accountAnnotations.Continuation.NextLinkUri));
}
using that method .Continuation is always null and accountAnnotations.Count is always 50 (but there are more than 50 records)
After struggling with .Continutation for a while I've come up with the following alternative method (but it seems "not good")
var accountAnnotationData = accountAnnotations.ToList();
var accountAnnotationFinal = accountAnnotations.ToList();
var index = 1;
while (accountAnnotationData.Count == 50)
{
accountAnnotationData = (from a in crmService.AnnotationSet
where a.ObjectId.Id == accountAnnotationData.First().ObjectId.Id
select a).Skip(50 * index).ToList();
accountAnnotationFinal = accountAnnotationFinal.Union(accountAnnotationData).ToList();
index++;
}
So the second method seems to work, but for any number of reasons it doesn't seem like the best. Is there a reason .Continuation is always null? Is there some setup step I'm missing or some nice way to do this?
The way to get the records from CRM is to use paging here is an example with a query expression but you can also use fetchXML if you want
// Query using the paging cookie.
// Define the paging attributes.
// The number of records per page to retrieve.
int fetchCount = 3;
// Initialize the page number.
int pageNumber = 1;
// Initialize the number of records.
int recordCount = 0;
// Define the condition expression for retrieving records.
ConditionExpression pagecondition = new ConditionExpression();
pagecondition.AttributeName = "address1_stateorprovince";
pagecondition.Operator = ConditionOperator.Equal;
pagecondition.Values.Add("WA");
// Define the order expression to retrieve the records.
OrderExpression order = new OrderExpression();
order.AttributeName = "name";
order.OrderType = OrderType.Ascending;
// Create the query expression and add condition.
QueryExpression pagequery = new QueryExpression();
pagequery.EntityName = "account";
pagequery.Criteria.AddCondition(pagecondition);
pagequery.Orders.Add(order);
pagequery.ColumnSet.AddColumns("name", "address1_stateorprovince", "emailaddress1", "accountid");
// Assign the pageinfo properties to the query expression.
pagequery.PageInfo = new PagingInfo();
pagequery.PageInfo.Count = fetchCount;
pagequery.PageInfo.PageNumber = pageNumber;
// The current paging cookie. When retrieving the first page,
// pagingCookie should be null.
pagequery.PageInfo.PagingCookie = null;
Console.WriteLine("#\tAccount Name\t\t\tEmail Address");while (true)
{
// Retrieve the page.
EntityCollection results = _serviceProxy.RetrieveMultiple(pagequery);
if (results.Entities != null)
{
// Retrieve all records from the result set.
foreach (Account acct in results.Entities)
{
Console.WriteLine("{0}.\t{1}\t\t{2}",
++recordCount,
acct.EMailAddress1,
acct.Name);
}
}
// Check for more records, if it returns true.
if (results.MoreRecords)
{
// Increment the page number to retrieve the next page.
pagequery.PageInfo.PageNumber++;
// Set the paging cookie to the paging cookie returned from current results.
pagequery.PageInfo.PagingCookie = results.PagingCookie;
}
else
{
// If no more records are in the result nodes, exit the loop.
break;
}
}
I am creating Rally Build Records as part of a TeamCity to Rally integration but havving issues associating a Build with a ChangeSet.
I find a set of related ChangeSets that match a particular criteria and have them in an array of String. I then create a JsonArray object, add these "_ref" strings as JsonPrimatives into the Array, add the array to my create Json object and add it to Rally.
However, what happens is that the build is created but the result has an empty Changeset array.
I have tried including the changesets in the createRequest and also doing an updateRequest but in both cases the response is SUCCESS, there are no errors or warnings reported and the Changeset array is returned as null and re-querying shows all other data as expected but the changeSet array is empty.
Here is the code.
JsonObject obj = new JsonObject();
obj.addProperty("Workspace", def.getWorkspace().getRef());
obj.addProperty("Duration",1.05);
obj.addProperty("Message", "Master 4683 Success");
obj.addProperty("Start", isoFormat.format(new Date()));
obj.addProperty("Status","SUCCESS");
obj.addProperty("Number","4683");
obj.addProperty("Uri", "http://");
obj.addProperty("BuildDefinition",def.getRef());
// changeSets is a ArrayList<String> of "_ref" strings of VALID changesets references.
if (changeSets != null && changeSets.size() > 0) {
JsonArray changeSetList = new JsonArray();
for (String id : changeSets) {
changeSetList.add(new JsonPrimitive(id));
}
obj.add("Changesets", changeSetList);
}
String ref = connector.Create("Build",obj);
connector.Delete(ref, null);
Any ideas?
My thought is that instead of populating your JsonArray with JsonPrimitive's having just the value of the ref, you actually need a JsonObject with a key/value pair of {"_ref", "/changeset/12345678910.js"}. I.E. make a change similar to the following:
// changeSets is a ArrayList<String> of "_ref" strings of VALID changesets references.
if (changeSets != null && changeSets.size() > 0) {
JsonArray changeSetList = new JsonArray();
for (String id : changeSets) {
JsonObject thisChangeset = new JsonObject();
thisChangeset.addProperty("_ref", id);
changeSetList.add(thisChangeset);
}
obj.add("Changesets", changeSetList);
}
And I believe your code should work as expected.
I know variants of this question have been asked before (even by me), but I still don't understand a thing or two about this...
It was my understanding that one could retrieve more documents than the 128 default setting by doing this:
session.Advanced.MaxNumberOfRequestsPerSession = int.MaxValue;
And I've learned that a WHERE clause should be an ExpressionTree instead of a Func, so that it's treated as Queryable instead of Enumerable. So I thought this should work:
public static List<T> GetObjectList<T>(Expression<Func<T, bool>> whereClause)
{
using (IDocumentSession session = GetRavenSession())
{
return session.Query<T>().Where(whereClause).ToList();
}
}
However, that only returns 128 documents. Why?
Note, here is the code that calls the above method:
RavenDataAccessComponent.GetObjectList<Ccm>(x => x.TimeStamp > lastReadTime);
If I add Take(n), then I can get as many documents as I like. For example, this returns 200 documents:
return session.Query<T>().Where(whereClause).Take(200).ToList();
Based on all of this, it would seem that the appropriate way to retrieve thousands of documents is to set MaxNumberOfRequestsPerSession and use Take() in the query. Is that right? If not, how should it be done?
For my app, I need to retrieve thousands of documents (that have very little data in them). We keep these documents in memory and used as the data source for charts.
** EDIT **
I tried using int.MaxValue in my Take():
return session.Query<T>().Where(whereClause).Take(int.MaxValue).ToList();
And that returns 1024. Argh. How do I get more than 1024?
** EDIT 2 - Sample document showing data **
{
"Header_ID": 3525880,
"Sub_ID": "120403261139",
"TimeStamp": "2012-04-05T15:14:13.9870000",
"Equipment_ID": "PBG11A-CCM",
"AverageAbsorber1": "284.451",
"AverageAbsorber2": "108.442",
"AverageAbsorber3": "886.523",
"AverageAbsorber4": "176.773"
}
It is worth noting that since version 2.5, RavenDB has an "unbounded results API" to allow streaming. The example from the docs shows how to use this:
var query = session.Query<User>("Users/ByActive").Where(x => x.Active);
using (var enumerator = session.Advanced.Stream(query))
{
while (enumerator.MoveNext())
{
User activeUser = enumerator.Current.Document;
}
}
There is support for standard RavenDB queries, Lucence queries and there is also async support.
The documentation can be found here. Ayende's introductory blog article can be found here.
The Take(n) function will only give you up to 1024 by default. However, you can change this default in Raven.Server.exe.config:
<add key="Raven/MaxPageSize" value="5000"/>
For more info, see: http://ravendb.net/docs/intro/safe-by-default
The Take(n) function will only give you up to 1024 by default. However, you can use it in pair with Skip(n) to get all
var points = new List<T>();
var nextGroupOfPoints = new List<T>();
const int ElementTakeCount = 1024;
int i = 0;
int skipResults = 0;
do
{
nextGroupOfPoints = session.Query<T>().Statistics(out stats).Where(whereClause).Skip(i * ElementTakeCount + skipResults).Take(ElementTakeCount).ToList();
i++;
skipResults += stats.SkippedResults;
points = points.Concat(nextGroupOfPoints).ToList();
}
while (nextGroupOfPoints.Count == ElementTakeCount);
return points;
RavenDB Paging
Number of request per session is a separate concept then number of documents retrieved per call. Sessions are short lived and are expected to have few calls issued over them.
If you are getting more then 10 of anything from the store (even less then default 128) for human consumption then something is wrong or your problem is requiring different thinking then truck load of documents coming from the data store.
RavenDB indexing is quite sophisticated. Good article about indexing here and facets here.
If you have need to perform data aggregation, create map/reduce index which results in aggregated data e.g.:
Index:
from post in docs.Posts
select new { post.Author, Count = 1 }
from result in results
group result by result.Author into g
select new
{
Author = g.Key,
Count = g.Sum(x=>x.Count)
}
Query:
session.Query<AuthorPostStats>("Posts/ByUser/Count")(x=>x.Author)();
You can also use a predefined index with the Stream method. You may use a Where clause on indexed fields.
var query = session.Query<User, MyUserIndex>();
var query = session.Query<User, MyUserIndex>().Where(x => !x.IsDeleted);
using (var enumerator = session.Advanced.Stream<User>(query))
{
while (enumerator.MoveNext())
{
var user = enumerator.Current.Document;
// do something
}
}
Example index:
public class MyUserIndex: AbstractIndexCreationTask<User>
{
public MyUserIndex()
{
this.Map = users =>
from u in users
select new
{
u.IsDeleted,
u.Username,
};
}
}
Documentation: What are indexes?
Session : Querying : How to stream query results?
Important note: the Stream method will NOT track objects. If you change objects obtained from this method, SaveChanges() will not be aware of any change.
Other note: you may get the following exception if you do not specify the index to use.
InvalidOperationException: StreamQuery does not support querying dynamic indexes. It is designed to be used with large data-sets and is unlikely to return all data-set after 15 sec of indexing, like Query() does.