There are simply 3 such entities. My goal is to find resources using gorm. But I want to find it based on a certain condition. Exactly what I want is to find the resources containing the specific word in the name of the service. How should I use a preload and where()
Related
I'm new to using ObjectBox, so I've been trying to do some experimenting with its query system to familarize myself with it. One of the queries I've been unable to do is a query comparing two properties. Ignoring the errors they throw, these are some examples of what I'm looking to do:
// Get objects where first number is bigger than second number
boxA.query(ObjectA_.firstNumber.greaterThan(ObjectA_.secondNumber))
// Get parent objects where one of its children has a specific value from the parent
parentBox.query().linkMany(ParentObject_.children, ChildObject_.name.equals(ParentObject_.favoriteChild));
I know based on this question that it's possible in Java using filters, but I also know that query filters are not in ObjectBox for Dart. One of the workaround I've been testing is querying for one property, getting the values, and using each value to query for the second property. But that becomes unsustainable at even moderately sized amounts of data.
If anyone knows of a "proper" way to do this without the use of Java filters, that would be appreciated. Otherwise, if there's a more performant workaround than the one I came up with, that would be great too.
There is no query filter API for Dart in ObjectBox, because Dart already has the where API.
E.g. for a result list write results.where((a) => a.firstNumber >= a.secondNumber).
I have a query which returns a number of ways. I want to find nodes matching certain criteria which appear within those ways. Note that the nodes I'm interested in do not form part of the way itself, but do appear within the bounds of the way. Also, the ways do not all have corresponding areas, so using the area search doesn't work in all cases.
I've got a minimal example which finds way 95677318, and I want to be able to find node 1552949334:
(
way({{bbox}})["man_made"="lighthouse"];
)->.searchArea;
/*doesn't work:*/
/*node(area.searchArea)["seamark:name"];*/
/*recur down and find node directly, just for the purpose of this question*/
(
.searchArea;>;
node({{bbox}})["seamark:name"];
);
out;
(Try it on https://overpass-turbo.eu/s/EpV)
This feature is not yet available as of release 0.7.55. In case there's no corresponding area available on the Overpass server, this kind of query is simply not feasible.
See https://github.com/drolbr/Overpass-API/issues/77 for details.
I need to build a custom id validator that will apply to a single collection, whose id will always be pre-defined (won't need a generator).
In the docs about id generators, it's written:
Currently the configuration of the custom generator applies to every resources (buckets, groups, collections, records). This tiny limitation can easily be fixed, don’t hesitate to get in touch with us!
But there is nothing documented about id validation.
So, how do I:
Implement an id validator, that
Will apply to one collection only?
By default cliquet uses a generator which accepts the following regular expression r'^[a-zA-Z0-9][a-zA-Z0-9_-]*$' (All letters and numbers + underscore and "-").
Before you chose to have a different ID validation mechanism, ensure you really need to.
Now, if that's not enough, you would need to select the proper validator depending on some configuration or already existing values, but this is not implemented in cliquet / kinto.
https://github.com/mozilla-services/cliquet/blob/master/cliquet/resource/init.py#L147 is probably a good place to look at / start with.
I'm trying to write a Cypher query to create multiple nodes and relationships in one query. The documentation on using CREATE clauses in Cypher states that it's not possible to create multiple nodes of different types in a singular CREATE clause.
However it hints that I should be able to break it up into multiple CREATE's. A couple of similar answers I have read point to the same solution as well. I've tried doing this and keep getting the response error.
Error: If you create multiple elements, you can only create one of each.
Here is a brief outline of what I'm trying to do.
Create an item node.
Create multiple representation nodes.
Create a relationship between the created item node and an existing stack node.
Create multiple relationships between the created item node and the created representation nodes.
This is the query I'm currently using which attempts to break up all the individual parts of the CREATE process into individual steps.
START stack=node({stack})
CREATE (item {item})
CREATE (representations {representations})
CREATE (stack)-[:Item]->(item)
CREATE (item)-[:Representation]->(representations)
RETURN item, representations
I've tried several variations of the above query, including putting the creation of the item and representation nodes at the beginning of the query.
I would really appreciate any advice. I really don't want to resort to making multiple database calls if it can be avoided.
Is your representations a list ? Then you can only have that as the single create statement.
I assume Neo4j 1.9 from your syntax.
What you can do though is to use FOREACH
START stack=node({stack})
CREATE (item {item})
CREATE (stack)-[:Item]->(item)
FOREACH (r in {representations} :
CREATE (representation {r}), (item)-[:Representation]->(representation)
)
MATCH (item)-[:Representation]->(representations)
RETURN item, representations
I have read about the Aggregate Pattern but I'm confused about something here. The pattern states that all the objects belonging to the aggregate should be accessed via the Aggregate Root, and not directly.
And I'm assuming that is the reason why they say you should have a single Repository per Aggregate.
But I think this adds a noticeable overhead to the application. For example, in a typical Web-based application, what if I want to get an object belonging to an aggregate (which is NOT the aggregate root)? I'll have to call Repository.GetAggregateRootObject(), which loads the aggregate root and all its child objects, and then iterate through the child objects to find the one I'm looking for. In other words, I'm loading lots of data and throwing them out except the particular object I'm looking for.
Is there something I'm missing here?
PS: I know some of you may suggest that we can improve performance with Lazy Loading. But that's not what I'm asking here... The aggregate pattern requires that all objects belonging to the aggregate be loaded together, so we can enforce business rules.
I'm not sure where you read about this "Aggregate Pattern". Please post a link.
One thing it could be is where we encapsulate a list into another object. For a simple example if we have a shopping cart instead of passing around a list of purchases we use a cart object instead. Then code that works on the whole cart (eg. getting total spend) can be encapsulated in the cart. I'm not sure if this is really a pattern but google found this link: http://perldesignpatterns.com/?AggregatePattern
I suspect when you say
"The aggregate pattern requires that
all objects belonging to the aggregate
be loaded together, so we can enforce
business rules. "
this depends on your business rules.
Generally patterns should not be regarded as a set of rules you must follow for everything. It is up to you as a developer to recognise where they can be used effectively.
In our cart example we would generally want to work on the whole cart at once. We might have business rules that say our customers can only order a limited about of items - or maybe they get a discount for order multiple items. So it makes sense to read the whole thing.
If you take a different example eg. products. You could still have a products repository but you needn't not load them all at once. You probably only ever want a page of products at a time.