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Include Compare Exchange Values
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Compare-Exchange items can be included when loading entities and when making queries.
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The Session tracks the included Compare Exchange items which means their value can be accessed
in that Session without making an additional call to the server. -
The Compare Exchange include syntax is based on the include method.
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In this page:
Syntax
Include method
Chain the method IncludeCompareExchangeValue() to include compare exchange values
along with Session.Load() or LINQ queries.
public interface ICompareExchangeValueIncludeBuilder<T, out TBuilder>
{
TBuilder IncludeCompareExchangeValue(string path);
TBuilder IncludeCompareExchangeValue(Expression<Func<T, string>> path);
TBuilder IncludeCompareExchangeValue(Expression<Func<T, IEnumerable<string>>> path);
}| Parameter | Type | Description |
|---|---|---|
| path | string;Expression<Func<T, string>>;Expression<Func<T, IEnumerable<string>>> |
The key of the compare exchange value you want to include, a path to the key, or a path to a string[] of keys. |
RQL
In an RQL query, you can use the include keyword
followed by cmpxchg() to include a compare exchange value:
include cmpxchg(key)In javascript functions within queries,
use includes.cmpxchg() (see the RawQuery example
below):
includes.cmpxchg(key);| Parameter | Type | Description |
|---|---|---|
| key | string;path to string |
The key of the compare exchange value you want to include, or a path to the key. |
Examples
using (IDocumentSession session = documentStore.OpenSession())
{
// Load a user document, include the compare exchange value
// with the key equal to the user's Name field
var user = session.Load<User>("users/1-A",
includes => includes.IncludeCompareExchangeValue(
x => x.Name));
// Getting the compare exchange value does not require
// another call to the server
var value = session.Advanced.ClusterTransaction
.GetCompareExchangeValue<string>(user.Name);
}using (IAsyncDocumentSession session = documentStore.OpenAsyncSession())
{
// Load a user document, include the compare exchange value
// with the key equal to the user's Name field
var user = await session.LoadAsync<User>("users/1-A",
includes => includes.IncludeCompareExchangeValue(
x => x.Name));
// Getting the compare exchange value does not require
// another call to the server
var value = await session.Advanced.ClusterTransaction
.GetCompareExchangeValueAsync<string>(user.Name);
}var users = session.Query<User>()
.Include(builder => builder.IncludeCompareExchangeValue(x => x.Name))
.ToList();
List<CompareExchangeValue<string>> compareExchangeValues = null;
// Getting the compare exchange values does not require
// additional calls to the server
foreach (User u in users){
compareExchangeValues.Add(session.Advanced.ClusterTransaction
.GetCompareExchangeValue<string>(u.Name));
}// First method: from body of query
var users1 = session.Advanced
.RawQuery<User>(@"
from Users as u
select u
include cmpxchg(u.Name)"
)
.ToList();
List<CompareExchangeValue<string>> compareExchangeValues1 = null;
// Getting the compare exchange values does not require
// additional calls to the server
foreach (User u in users1){
compareExchangeValues1.Add(session.Advanced.ClusterTransaction
.GetCompareExchangeValue<string>(u.Name));
}
// Second method: from a JavaScript function
var users2 = session.Advanced
.RawQuery<User>(@"
declare function includeCEV(user) {
includes.cmpxchg(user.Name);
return user;
}
from Users as u
select includeCEV(u)"
)
.ToList();
// Note that includeCEV() returns the same User
// entity it received, without modifying it
List<CompareExchangeValue<string>> compareExchangeValues2 = null;
// Does not require calls to the server
foreach (User u in users2){
compareExchangeValues2.Add(session.Advanced.ClusterTransaction
.GetCompareExchangeValue<string>(u.Name));
}
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