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    Patching: How to Perform Single Document Patch Operations

    The Patch operation is used to perform partial document updates without having to load, modify, and save a full document. The whole operation is executed on the server side and is useful as a performance enhancement or for updating denormalized data in entities.

    The current page deals with patch operations on single documents.

    Patching has three possible interfaces: Typed Session API, Non-Typed Session API, and Operations API.

    Patching can be done from the client as well as in the studio.

    API Overview

    Typed Session API

    A type safe session interface that allows performing the most common patch operations.
    The patch request will be sent to server only after the call to SaveChanges. This way it's possible to perform multiple operations in one request to the server.

    Increment Field Value

    Session.Advanced.Increment 

    void Increment<T, U>(T entity, Expression<Func<T, U>> fieldPath, U delta);

void Increment<T, U>(string id, Expression<Func<T, U>> fieldPath, U delta);
    Parameters
    T Type Entity type
    U Type Field type, must be of numeric type or a string of char for string concatenation
    entity T Entity on which the operation should be performed. The entity should be one that was returned by the current session in a Load or Query operation, this way, the session can track down the entity's ID
    entity id string Entity ID on which the operation should be performed.
    fieldPath Expression<Func<T, U>> Lambda describing the path to the field.
    delta U Value to be added.

    Set Field Value

    Session.Advanced.Patch 

    void Patch<T, U>(string id, Expression<Func<T, U>> fieldPath, U value);

void Patch<T, U>(T entity, Expression<Func<T, U>> fieldPath, U value);
    Parameters
    T Type Entity type
    U Type Field type
    entity T Entity on which the operation should be performed. The entity should be one that was returned by the current session in a Load or Query operation. This way the session can track down the entity's ID.
    entity id string Entity ID on which the operation should be performed.
    fieldPath Expression<Func<T, U>> Lambda describing the path to the field.
    delta U Value to set.

    Array Manipulation

    Session.Advanced.Patch 

    void Patch<T, U>(T entity, Expression<Func<T, IEnumerable<U>>> fieldPath,
    Expression<Func<JavaScriptArray<U>, object>> arrayMofificationLambda);

void Patch<T, U>(string id, Expression<Func<T, IEnumerable<U>>> fieldPath,
    Expression<Func<JavaScriptArray<U>, object>> arrayMofificationLambda);
    Parameters
    T Type Entity type
    U Type Field type
    entity T Entity on which the operation should be performed. The entity should be one that was returned by the current session in a Load or Query operation. This way the session can track down the entity's ID.
    entity id string Entity ID on which the operation should be performed.
    fieldPath Expression<Func<T, U>> Lambda describing the path to the field.
    arrayMofificationLambda Expression<Func<JavaScriptArray<U>, object>> Lambda that modifies the array, see JavaScriptArray below.

    JavaScriptArray

    JavaScriptArray allows building lambdas representing array manipulations for patches.

    Method Signature Return Type Description
    Put(T item) JavaScriptArray Allows adding item to an array.
    Put(params T[] items) JavaScriptArray Items to be added to the array.
    RemoveAt(int index) JavaScriptArray Removes item in position index in array.
    RemoveAll(Func<T, bool> predicate) JavaScriptArray Removes all the items in the array that satisfy the given predicate.

    Non-Typed Session API

    The non-typed Session API for patches uses the Session.Advanced.Defer function which allows registering one or more commands.
    One of the possible commands is the PatchCommandData, describing single document patch command.
    The patch request will be sent to server only after the call to SaveChanges, this way it's possible to perform multiple operations in one request to the server.

    Session.Advanced.Defer 

    void Defer(ICommandData[] commands);

    PatchCommandData

    Constructor
    id string ID of the document to be patched.
    changeVector string [Can be null] Change vector of the document to be patched, used to verify that the document was not changed before the patch reached it.
    patch PatchRequest Patch request to be performed on the document.
    patchIfMissing PatchRequest [Can be null] Patch request to be performed if no document with the given ID was found.

    PatchRequest

    We highly recommend using scripts with parameters. This allows RavenDB to cache scripts and boost performance. Parameters can be accessed in the script through the args object, and passed using PatchRequest's "Values" parameter.

    Members
    Script string JavaScript code to be run.
    Values Dictionary<string, object> Parameters to be passed to the script. The parameters can be accessed using the '$' prefix. Parameter starting with a '$' will be used as is, without further concatenation .

    Operations API

    An operations interface that exposes the full functionality and allows performing ad-hoc patch operations without creating a session.

    Raven.Client.Documents.Operations.Send
    Raven.Client.Documents.Operations.SendAsync 

    PatchStatus Send(PatchOperation operation);

Task<PatchStatus> SendAsync(PatchOperation operation, 
                            SessionInfo sessionInfo = null, 
                            CancellationToken token = default(CancellationToken));

    PatchOperation

    Constructor
    id string ID of the document to be patched.
    changeVector string [Can be null] Change vector of the document to be patched, used to verify that the document was not changed before the patch reached it.
    patch PatchRequest Patch request to be performed on the document.
    patchIfMissing PatchRequest [Can be null] Patch request to be performed if no document with the given ID was found. Will run only if no changeVector was passed.
    skipPatchIfChangeVectorMismatch bool If false and changeVector has value, and document with that ID and change vector was not found, will throw exception.

    List of Script Methods

    This is a list of a few of the javascript methods that can be used in patch scripts. See the more comprehensive list at Knowledge Base: JavaScript Engine.

    Method Arguments Description
    load string or string[] Loads one or more documents into the context of the script by their document IDs
    loadPath A document and a path to an ID within that document Loads a related document by the path to its ID
    del Document ID; change vector Delete the given document by its ID. If you add the expected change vector and the document's current change vector does not match, the document will not be deleted.
    put Document ID; document; change vector Create or overwrite a document with a specified ID and entity. If you try to overwrite an existing document and pass the expected change vector, the put will fail if the specified change vector does not match the document's current change vector.
    cmpxchg Key Load a compare exchange value into the context of the script using its key
    getMetadata Document Returns the document's metadata
    id Document Returns the document's ID
    lastModified Document Returns the DateTime of the most recent modification made to the given document
    counter Document; counter name Returns the value of the specified counter in the specified document
    counterRaw Document; counter name Returns the specified counter in the specified document as a key-value pair
    incrementCounter Document; counter name Increases the value of the counter by one
    deleteCounter Document; counter name Deletes the counter

    Examples

    Change Field's Value

    // change FirstName to Robert                
session.Advanced.Patch<Employee, string>(
    "employees/1",
    x => x.FirstName, "Robert");

session.SaveChanges();
    // change FirstName to Robert                
session.Advanced.Defer(new PatchCommandData(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.FirstName = args.FirstName;",
        Values =
        {
            {"FirstName", "Robert"}
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    // change FirstName to Robert                
store.Operations.Send(new PatchOperation(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.FirstName = args.FirstName;",
        Values =
        {
            {"FirstName", "Robert"}
        }
    },
    patchIfMissing: null));

    Change Values of Two Fields

    // change FirstName to Robert and LastName to Carter in single request
// note that in this case, we create single request, but two seperate batch operations
// in order to achieve atomicity, please use the non generic APIs
session.Advanced.Patch<Employee, string>("employees/1", x => x.FirstName, "Robert");
session.Advanced.Patch<Employee, string>("employees/1", x => x.LastName, "Carter");

session.SaveChanges();
    // change FirstName to Robert and LastName to Carter in single request
// note that here we do maintain the atomicity of the operation
session.Advanced.Defer(new PatchCommandData(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"
                this.FirstName = args.UserName.FirstName
                this.LastName = args.UserName.LastName",
        Values =
        {
            {
                "UserName", new
                {
                    FirstName = "Robert",
                    LastName = "Carter"
                }
            }
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    // change FirstName to Robert and LastName to Carter in single request
// note that here we do maintain the atomicity of the operation
store.Operations.Send(new PatchOperation(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"
                this.FirstName = args.UserName.FirstName
                this.LastName = args.UserName.LastName",
        Values =
        {
            {
                "UserName", new
                {
                    FirstName = "Robert",
                    LastName = "Carter"
                }
            }
        }
    }, patchIfMissing: null));

    Increment Value

    // increment UnitsInStock property value by 10
session.Advanced.Increment<Product, int>("products/1-A", x => x.UnitsInStock, 10);

session.SaveChanges();
    session.Advanced.Defer(new PatchCommandData(
    id: "products/1-A",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.UnitsInStock += args.UnitsToAdd",
        Values =
        {
            {"UnitsToAdd", 10}
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    store.Operations.Send(new PatchOperation(
    id: "products/1-A",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.UnitsInStock += args.UnitsToAdd",
        Values =
        {
            {"UnitsToAdd", 10}
        }
    },
    patchIfMissing: null));

    Add Item to Array

    // add a new comment to Comments
session.Advanced.Patch<BlogPost, BlogComment>("blogposts/1",
    x => x.Comments,
    comments => comments.Add(new BlogComment
    {
        Content = "Lore ipsum",
        Title = "Some title"
    }));

session.SaveChanges();
    // add a new comment to Comments
session.Advanced.Defer(new PatchCommandData(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.push(args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }

    },
    patchIfMissing: null));

session.SaveChanges();
    // add a new comment to Comments
store.Operations.Send(new PatchOperation(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.push(args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }

    },
    patchIfMissing: null));

    Insert Item into Specific Position in Array

    Inserting item into specific position is supported only by the non-typed APIs 

    // insert a new comment at position 1 to Comments
session.Advanced.Defer(new PatchCommandData(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.splice(1,0,args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    store.Operations.Send(new PatchOperation(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.splice(1,0,args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }
    },
    patchIfMissing: null));

    Modify Item in Specific Position in Array

    Inserting item into specific position is supported only by the non-typed APIs 

    // modify a comment at position 3 in Comments
session.Advanced.Defer(new PatchCommandData(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.splice(3,1,args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    // modify a comment at position 3 in Comments
store.Operations.Send(new PatchOperation(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = "this.Comments.splice(1,0,args.Comment)",
        Values =
        {
            {
                "Comment", new BlogComment
                {
                    Content = "Lore ipsum",
                    Title = "Some title"
                }
            }
        }
    },
    patchIfMissing: null));

    Filter out Items from an Array

    // filter out all comments of a blogpost which contains the word "wrong" in their contents 
session.Advanced.Patch<BlogPost, BlogComment>("blogposts/1",
    x => x.Comments,
    comments => comments.RemoveAll(y => y.Content.Contains("wrong")));

session.SaveChanges();
    // filter out all comments of a blogpost which contains the word "wrong" in their contents 
session.Advanced.Defer(new PatchCommandData(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.Comments = this.Comments.filter(comment=>
                comment.Content.includes(args.TitleToRemove));",
        Values =
        {
            {"TitleToRemove", "wrong"}
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    // filter out all comments of a blogpost which contains the word "wrong" in their contents
store.Operations.Send(new PatchOperation(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.Comments = this.Comments.filter(comment=>
                comment.Content.includes(args.TitleToRemove));",
        Values =
        {
            {"TitleToRemove", "wrong"}
        }
    },
    patchIfMissing: null));

    Loading Documents in a Script

    Loading documents supported only by non-typed APIs 

    // update product names in order, according to loaded product documents
session.Advanced.Defer(new PatchCommandData(
    id: "orders/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.Lines.forEach(line=> { 
                var productDoc = load(line.Product);
                line.ProductName = productDoc.Name;
                });"
    }, patchIfMissing: null));

session.SaveChanges();
    // update product names in order, according to loaded product documents
store.Operations.Send(new PatchOperation(
    id: "blogposts/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"this.Lines.forEach(line=> { 
                var productDoc = load(line.Product);
                line.ProductName = productDoc.Name;
                });"
    },
    patchIfMissing: null));

    Remove Property

    Removing property supported only by the non-typed APIs 

    // remove property Age
session.Advanced.Defer(new PatchCommandData(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"delete this.Age"
    },
    patchIfMissing: null));
session.SaveChanges();
    // remove property Age
store.Operations.Send(new PatchOperation(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @"delete this.Age"
    },
    patchIfMissing: null));

    Rename Property

    Renaming property supported only by the non-typed APIs 

    // rename FirstName to First
session.Advanced.Defer(new PatchCommandData(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @" var firstName = this[args.Rename.Old];
                delete this[args.Rename.Old];
                this[args.Rename.New] = firstName",
        Values =
        {
            {
                "Rename", new
                {
                    Old = "FirstName",
                    New = "Name"
                }
            }
        }
    },
    patchIfMissing: null));

session.SaveChanges();
    store.Operations.Send(new PatchOperation(
    id: "employees/1",
    changeVector: null,
    patch: new PatchRequest
    {
        Script = @" var firstName = this[args.Rename.Old];
                delete this[args.Rename.Old];
                this[args.Rename.New] = firstName",
        Values =
        {
            {
                "Rename", new
                {
                    Old = "FirstName",
                    New = "Name"
                }
            }
        }
    },
    patchIfMissing: null));

    Add Document

    Adding a new document is supported only by the non-typed APIs 

    session.Advanced.Defer(new PatchCommandData("employees/1-A", null,
    new PatchRequest
    {
        Script = "put('orders/', { Employee: id(this) });",
    }, null));

session.SaveChanges();
    store.Operations.Send(new PatchOperation("employees/1-A", null, new PatchRequest
{
    Script = "put('orders/', { Employee: id(this) });",
}));

    Clone Document

    In order to clone a document use put method as follows 

    session.Advanced.Defer(new PatchCommandData("employees/1-A", null,
    new PatchRequest
    {
        Script = "put('employees/', this);",
    }, null));

session.SaveChanges();
    store.Operations.Send(new PatchOperation("employees/1-A", null, new PatchRequest
{
    Script = "put('employees/', this);",
}));

    Cloning, Attachments & Counters

    The attachments and/or counters from source document will not be copied to the new one automatically.

    Increment Counter

    In order to increment or create a counter use incrementCounter method as follows 

    var order = session.Load<Order>("orders/1-A");
session.CountersFor(order).Increment("Likes", 1);
session.SaveChanges();
    session.Advanced.Defer(new PatchCommandData("orders/1-A", null,
    new PatchRequest
    {
        Script = "incrementCounter(this.Company, args.name, args.val);",
        Values =
        {
            { "name", "Likes" },
            { "val", 20 }
        }
    }, null));
session.SaveChanges();
    store.Operations.Send(new PatchOperation("orders/1-A", null, new PatchRequest
{
    Script = "incrementCounter(this.Company, args.name, args.val);",
    Values =
    {
        { "name", "Likes" },
        { "val", -1 }
    }
}));

    Method Overloading & Value restrictions

    The method can be called by document ID or by document reference and the value can be negative

    Delete Counter

    In order to delete a counter use deleteCounter method as follows 

    session.CountersFor("orders/1-A").Delete("Likes");
session.SaveChanges();
    session.Advanced.Defer(new PatchCommandData("products/1-A", null,
    new PatchRequest
    {
        Script = "deleteCounter(this, args.name);",
        Values =
        {
            { "name", "Likes" },
        }
    }, null));
session.SaveChanges();
    store.Operations.Send(new PatchOperation("products/1-A", null, new PatchRequest
{
    Script = "deleteCounter(this, args.name);",
    Values =
    {
        { "name", "Likes" },
    }
}));

    Method Overloading

    The method can be called by document ID or by document reference

    Get Counter

    In order to get a counter while patching use counter method as follows 

    var order = session.Load<Order>("orders/1-A");
var counters = session.Advanced.GetCountersFor(order);
    session.Advanced.Defer(new PatchCommandData("orders/1-A", null,
    new PatchRequest
    {
        Script = @"var likes = counter(this.Company, args.name);
                   put('result/', {company: this.Company, likes: likes});",
        Values =
        {
            { "name", "Likes" },
        }
    }, null));
session.SaveChanges();
    store.Operations.Send(new PatchOperation("orders/1-A", null, new PatchRequest
{
    Script = @"var likes = counter(this.Company, args.name);
               put('result/', {company: this.Company, likes: likes});",
    Values =
    {
        { "name", "Likes" },
    }
}));

    Method Overloading

    The method can be called by document ID or by document reference

    related articlesRelated Articles

    Patching

    Knowledge Base

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