Develop Reference

Finding a list of related objects by ID

Let's say for example I have a bridge table called PersonAnimal. I want to search for all the people who have a given animal's ID. The query so far looks like:
Animal animal = getById(Animal.class, animalId)
ObjectSelect
.query(PersonAnimal.class)
.where(PersonAnimal.ANIMAL.eq(animal))
.select(context)
However the first line in the above code segment shows that I first have to retrieve the related object from the database. I want to get rid of that database lookup and instead do something like:
ObjectSelect
.query(PersonAnimal.class)
.where(PersonAnimal.ANIMAL_ID.eq(animalId)) // <- Find by ID instead
.select(context)
Is that possible?
I am running version 4.1 of the Apache Cayenne ORM.

Just as I posted the question I found the answer. You need to create an Expression using a Property object like so:
val findByIdExpr = Property.create(PersonAnimal.ANIMAL.name, Long::class.java).eq(yourId)
val gotList = ObjectSelect
.query(PersonAnimal.class)
.where(findByIdExpr)
.select(context)
Above code is in Kotlin but is also easy to understand from a Java perspective.

Retrieving exact node id in neo4j cypher

I'm using neo4j-jdbc 2.3.2 as my neo4j client for java. When I executed following cypher query
match(p:Person) where p.id_number='761201948V' return p.id; it will return P2547228 as node id. I feel like id is same as other properties of the node as I can use it inside where clauses. But here I'm expecting an integer which can use inside this query START p=node('node.id') return p; Is this id is an internal thing to neo4j db? and is there a way to retrieve this id?
From the following two cyphers what is most efficient one?(if both referring same node)
START p=node('2547223') return p;
match(p:Person) where p.id='P2547228' return p;

You have to use the ID(x) function for this. Note, that ID(x) and x.id are a complete different thing. The former returns the internal node/relationship id managed by Neo4j itself. The latter gives the id property which is managed by the user and not by the database itself.
Also note, that a node/relationship ID is always numeric.
Using START is pretty much old school and shouldn't be used any more (except for accessing manual indexes):
start p=node(2547228) return p
This one is a equivalent statement. It is highly efficient since it just needs to do a simple seek operation on the node store:
match(p:Person) where id(p)=2547228 return p;
Looking for a property requires either a node label scan or a schema index lookup:
match(p:Person) where p.id=2547228 return p;
Just check out the query plans on your own by prefixing the statement with PROFILE.

Lotus getting field from database

I am new to lotus. I need to get some info from Lotus database with Java. I have database:
Session session = NotesFactory.createSession(host, user, pwd);
Database database = session.getDatabase(server, database);
I have that info:
field - fldContractorCode;
form - form="formAgreement";
For example field is "abcde";
So how I can get info from that database? I need to use seatch formula? Or what methods I need to use? Thanx for help.
UPD
Now I am using such way:
DocumentCollection collection = DATABASE.search("form=\"formAgreement\"");
Document doc = collection.getFirstDocument();
while(doc != null) {
doc.getItemValueString("fldContractorCode");
doc = collection.getNextDocument();
}
And it works fine for me, but I think that way is not very comfortable because to find some document for example with field="abcd" I need to itearte over collection every time...
So that why I am asking for some way to find document by the field value. And I dont understand what is VIEW in database and where to get this VIEW name.

In your existing code, you can just change one line:
DocumentCollection collection = DATABASE.search("form=\"formAgreement\ & "fldContractorCode=\"abcd\"");
However, this will be slow if the database contains many documents. For best performance, you should consider using Domino Designer to add a new view to your database and using the getDocumentByKey() method suggested in the other answers. If that is not an option, Simon's suggestion of using the FTSearch() method is faster than the Search() method, but only if a full text index exists for the database. It also has a slightly different syntax for the search string.

There are a number of ways to get the document.
1. Search for the document from a view, where the first column of the view contains a sorted value of the fldContractorCode.
For example:
String key = "abide";
View view = db.getView("viewName");
Document doc = view.getDocumentByKey(key, true);
2. You can use the Database FTSearch Method to do a full text search to find the document. You will need the database to have a full text index created.
3. If you know the UNID or notes ID of the document you can use getDocumentByUNID() or getDocumentByID().
Your question is quite broad, so I recommend reading the Infocenter as it details sample code for each method.
http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/topic/com.ibm.designer.domino.main.doc/H_NOTESDATABASE_CLASS_JAVA.html

You will have to drill down to the DOCUMENT (not Form) you want to retrieve the field from.
Lotus Notes has a very easy to understand hierarchical way to get to where you want. You will need to instantiate objects in this sequence:
Session
Database
View
Document
Let's say you have a view called $(sysAgreements) that list all forms "formAgreement".
Its selection formula would be something like this:
SELECT Form="formAgreement"
To get to the document or documents you want you will do something like this:
Session session = NotesFactory.createSession(host, user, pwd);
Database database = session.getDatabase(server, database);
View view = database.getView("$(sysAgreements)");
Document doc = view.getDocumentByKey(VIEW_KEY);
String fieldContent = doc.getItemValueString("fldContractorCode");
There are several ways to retrieve info from a Notes database. This is one of them. Bear in mind that they key used by Notes to search a view with getDocumentByKey is the 1st sorted column.
If you want to get multiple documents you can use:
DocumentCollection docCol = view.getAllDocumentsByKey(VIEW_KEY);
and then iterate over it.
Avoid doing ftsearch because it's slow and a bit painful to Notes. Prefere looking up in the views.
Also another powerful source of help is the Notes help. Get the help database from a computer that has the Notes Development Client installed. But pay attention to the name of the help you're picking, there are 3 helps in Notes: the client, development and administration. Development is what you want.

Order by another table with Liferay's DynamicQuery

I have a problem while I'm making a Dynamic Query in Liferay 6. I'm trying to make a query to order JournalArticles based on their view count. The view count is specified in another table (AssetEntry).
I'm stuck with this:
DynamicQuery query = DynamicQueryFactoryUtil.forClass(
JournalArticle.class, "articleParent", PortalClassLoaderUtil.getClassLoader());
//adding criterions
query.add(...);
DynamicQuery dq0 = DynamicQueryFactoryUtil.forClass(AssetEntry.class, "asset",
PortalClassLoaderUtil.getClassLoader())
.setProjection(ProjectionFactoryUtil.property("asset.classPK"))
.add(PropertyFactoryUtil.forName("asset.companyId")
.eqProperty("articleParent.companyId"))
.add(PropertyFactoryUtil.forName("asset.groupId")
.eqProperty("articleParent.groupId"));
query.add(PropertyFactoryUtil.forName("articleParent.resourcePrimKey").in(dq0))
.addOrder(OrderFactoryUtil.desc("asset.viewCount"));
With this I get an error message saying: could not resolve property: asset of: com.liferay.portlet.journal.model.impl.JournalArticleImpl.
If I remove the addOrder-call, this error disappears. How should I add the order statement so the main query is aware of asset.viewCount?

AssetEntryQuery assetEntryQuery = new AssetEntryQuery();
assetEntryQuery.setClassName(JournalArticle.class.getName());
assetEntryQuery.setXXX //adding criterions
assetEntryQuery.setOrderByCol1("viewCount");
List<AssetEntry> assetEntries = AssetEntryServiceUtil.getEntries(assetEntryQuery);

I am afraid that there is no direct way to do this with the DynamicQuery API.
I think you would need to use Service builder Finders i.e. Custom Query with Service builder.

You can't use dynamic query because there is no direct reference from JournalArticle entity to AssetEntry entity.
One possibility is to retrieve ordered ids of articles from the AssetEntry table (basically you dq0), then do another query and do the sorting programatically (you have the ids ordered).
Finally I think that this line
query.add(PropertyFactoryUtil.forName("articleParent.resourcePrimKey").in(dq0))
doesn't do what you think it does. resoucePrimKey is reference to resource table for permissions. You need to use id column.

GAE Datastore querying by index

I have created entities in the datastore. I want to use the index assigned to them by the datstore for queries.
i.e get an iterable back where the id is greater than a given number
e.g.
Query q = new Query("MyEntity");
q.addFilter("id",Query.FilterOperator.GREATER_THAN_OR_EQUAL, startId);
PreparedQuery pq = datastore.prepare(q);
I know I can get back an individual entity back via id - but how to get a list ?
Cheers,

Iterable<Entity> myEntities = pq.asIterable();
List<Entity> myEntitiesInAList = pq.asList(FetchOptions.Builder.withChunkSize(500));
Side note:
"id" is not the name of the key assigned automatically by App Engine. I think you must use __key__ as the property name to do queries on it, and construct a full key as the search parameter, not just the long id.

If your intent is to remember where you left off and continue there on a subsequent query, consider using a query cursor. The example on that page might give you some further options.