In my application there are already many nodes with different labels. We are passing property value at the time of creation. I wanted to have 2 properties for all the nodes by default (like creationDate and createdBy). Is there any possibility from configuration side that we can pass these property by default to all the nodes at the time of creation.
If by configuration, you only mean neo4j.conf, then no. You need some code to actually compute the value of the properties anyway: how do you represent the date, how do you determine who created the node?
To do that, you could deploy an extension in Neo4j to intercept the creation of nodes through transaction events by implementing a TransactionEventHandler: you'll get the TransactionData which directly exposes the nodes that were created, on which you can then set the audit properties you want.
The handler is registered through GraphDatabaseService, which can be obtained at startup by implementing PluginLifecycle and exposing the implementation via the Service Locator mechanism (put the class name in META-INF/services/org.neo4j.server.plugins.PluginLifecycle).
Related
The documentation mentions that extended properties are a finite resource in a user's mailbox, and exceeding this limit will result in unexpected errors when trying to create new properties.
It is not mentioned explicitly anywhere that I could if item customProperties, as written to through the Office.js client, has the same limitation. Does it?
We plan to optionally write a small amount of data to item customProperties if the user modifies inputs exposed in our Add-in Taskpane in the Outlook client. These properties will later be read by a server consuming changed events through the events delta API.
Will we eventually run into issues with this approach if we don't implement some sort of "garbage collection" of no longer used customProperties?
Item custom Properties are extended properties https://learn.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxcext/4cf1da5e-c68e-433e-a97e-c45625483481?redirectedfrom=MSDN
So you have one extended property and then the value is a Json Key pair so one Extended property provides multiple custom properties (up to the limitation of the size of the Extended property)
Even if you don't want to use Item Custom properties its a good idea to follow the same approach eg create one extended property for your app and then store what ever combination of property values you need as a JSON structure in the value on the property. Its not a good idea to have your application creating random/multiple custom properties as you will easily exhaust them/create a mess and there is no advantage in doing it that way.
I created a web application that use a Neo4j database and I need to know when a property is created or modified by an user.
Do you have any advices for me?
I thought to modify every property in an array where there will be the real value of property and a timestamp value (but I don't know how to do).
https://facebook.github.io/relay/graphql/objectidentification.htm is very clear around what Node is and how it behaves, but it doesn't specify which objects must implement it, or what the consequences are if your object doesn't implement it. Is there a set of features that don't work? Are such objects completely ignored? Not all objects in the existing spec (e.g. pageInfo) implement it, so it's clearly not universally required, but pageInfo is somewhat of a special case.
Another way of thinking about the Node interface is that objects that implement it are refetchable. Refetchability effectively means that an object has an ID that I can use to identify the object and retrieve it; by convention, these IDs will usually be opaque, but will contain type information and an identifier within that type (eg. a Base-64 encoding of a string like "Account:1234").
Relay will leverage refetchability in two ways:
Under a process known as "diffing", if you already have some data for an object identified by ID QWNjb3VudDoxMjM0 (say, the name and address fields), and you then navigate to a view where we show some additional fields (location, createdAt) then Relay can make a minimal query that "refetches" the node but only requests the missing fields.
Relatedly, Relay will diff connections and will make use of the Node interface to fill in missing data on those (example: through some combination of navigation you might have full information for some items in a view, but need to fill in location for some items within the range, or you might modify an item in a connection via a mutation). So, in basic pagination, Relay will often end up making a first + after query to extend a connection, but if you inspect its network traffic in a real app you will also see that it makes node queries for items within connections.
So yes, you're right that pageInfo doesn't implement Node, and it wouldn't really make sense for it to do so.
I am attempting to implement zookeeper as a shared state engine for an application I am creating in erlang. The structure for the state would be like the following:
/appRoot
/parent1:{json}
/child1:{json}
/child2:{json}
/parent2:{json}
/child1:{json}
/child2:{json}
I would like to be able to have a single method that returned all parent nodes when provided /appRoot along with it's data. Say in a list of tuples [{parent1,{json}}, {parent2:{json}}]. Or, if provided /appRoot/parent1 a list of it's subnodes with the data. So far, all I see is a way to get the keys (getChildren) then recursively retrieve the data with the key. It seems like I should be able to just make one call to do this.
I am currently using the ezk erlang client library. If anybody knows a better solution, that would be appreciated as well.
TIA
AFAIK there is no way to atomically list node children along with its data in zookeeper wire protocol. Seems, there is only way to do this is following:
List all node children and monitor children changes.
For each child node read it data and monitor data changes.
Update corresponding values on each children change happened after you started traversal.
This can be easily done over ezk, but I've not provided any example code because it heavily depends on guarantees of atomicity that your app logic demanded.
The spring data neo4j can put a "Person" into neo4j with two labels ("Person", "_Person").
How can I change it to com.xxxx.xxxx.Person?
Are there two classes named Person in different packages?
Slightly buried towards the end of the documentation you will find Section 20.15 Entity Type Representation.
As some type information is also stored in labels, node/relationship-properties and/or indexes it might amount to a substantial amount of data in the graph. It is possible to use an #TypeAlias("name") annotation on nodes and relationships to have a short constant name for each type which is (unlike the default approach) renaming-refactoring-safe. From 3.0 onwards, Spring Data Neo4j uses the simple class name as the default whilst previous versions used to default to the fully qualified name. If you would like to use the fully qualified class name by default, you can
Register a Neo4jMappingContext bean configured with an instance of org.springframework.data.neo4j.support.mapping.ClassNameAlias
Override the spring "entityAlias" bean with an instance of org.springframework.data.neo4j.support.mapping.ClassNameAlias. For example, using XML config this would look as follows:
<bean id="entityAlias" class="org.springframework.data.neo4j.support.mapping.ClassNameAlias" />
As to why you want two different classes named Person in your domain, that's another question...