Assume I have the following as the value in an IMap:
public class Employee{
public int empId;
public List<String> categories;
public List<String> getCategories(){
return this.categories;
}
}
I would like to find all employees that belong to category "Sales". Also, I would like to create an index on getCategories() so that the query returns fast. There seems to be no Predicate available to do this. How do I go about achieving this? It seems like I will have to write a Predicate to do this. Is there example code I can look at that would show me how to build a predicate that uses an index ?
The only way I currently see this happening is to denormalize the data model and use something like a IMap and the following as value:
class EmployeeCategory{int employeeId, String category}
And put an index on category.
It is somewhere on the backlog to provide more advances indices that should be able to do this out of the box.
I tried by iterating the List to a separate Imap and then querying it in the client.
IMap<String,ArrayList< categories >> cache=hazelcastInstance.getMap("cache");
IMap<String, categories> cachemodified = hazelcastInstance.getMap("cachemodified") ;
int[] idx = { 0 };
xref.get("urkey").forEach(cachefelement ->{
cachemodified.put(String.valueOf(idx[0]++),cachefelement);
});
Predicate p = Predicates.equal("categoryId", "SearchValue");
Collection<categories> result = cachemodified.values(p);
Related
I'm new to JOOQ and currently fail to map a joined query to Map<K, List<V>>: the list always only contains one element.
Here's my code:
DSL.using(...)
.select(ORDER.fields())
.select(ORDER_ITEM_ARTICLE.fields())
.from(ORDER)
.leftOuterJoin(ORDER_ITEM_ARTICLE).on(ORDER.ID.eq(ORDER_ITEM_ARTICLE.ORDER_ID))
// to Map<InOutOrder, List<OrderItemArticle>>
.fetchGroups(
r -> r.into(ORDER).into(InOutOrder.class),
r -> r.into(ORDER_ITEM_ARTICLE).into(OrderItemArticle.class)
)
// map to InOutOrder
.entrySet().stream().map( e -> {
// e.getValue() always returns list with only 1 element?!
e.getKey().articles = e.getValue();
return e.getKey();
})
.collect(Collectors.toList())
;
Say I have 1 row in ORDER and 2 corresponding rows in ORDER_ITEM_ARTICLE. Running the SQL returned by .getSQL() (after .fetchGroups()), returns me 2 rows as expected, so I assumed the fetchGroups() call will populate my list with two entries as well?!
What am I missing?
Thanks!
Update:
As requested, the InOutOrder class:
public class InOutOrder extends Order {
public List<OrderItemArticle> articles;
public List<OrderItemOther> others;
public List<OrderItemCost> costs;
public List<OrderContact> contacts;
public List<EmailJob> emailJobs;
}
So this is just an extension of the JOOQ POJO class and is used for JSON communication with the API clients...
fetchGroups() simply puts objects in a LinkedHashMap. You have to adhere to the usual Map contract, which means implementing equals() and hashCode(). Without it, each object you're creating (or which jOOQ is creating for you) will use identity comparison, so you get every "value" only once in the result.
I have a map1 which holds the information as
[40256942,6] [60246792,5]
Now that I want to prepare a map2 that holds information such as
itemNo, 40256942
qty, 6
itemNo, 60246792
qty, 5
to prepare final information as json
“partialArticlesInfo”: [{itemNo:”40256942”, availQty:”6”}, {itemNo:”60246792”, availQty:”5”}]
I am trying to iterate map1 to retrieve values and set that against the key. But I am getting only one entry which is last one. Is there any way , I get the new map with entries such as mentioned above
Map<String, String> partialArticlesInfo = new HashMap<String,String>();
Map<String, String> partialArticlesTempMap = null;
for (Map.Entry<String,String> entry : partialStockArticlesQtyMap.entrySet())
{
partialArticlesTempMap = new HashMap<String,String>();
partialArticlesTempMap.put("itemNo",entry.getKey());
partialArticlesTempMap.put("availQty",entry.getValue());
partialArticlesInfo.putAll(partialArticlesTempMap);
}
In Java (I'm assuming you're using Java, in the future it would be helpful to specify that) and every other language I know of, a map holds mappings between keys and values. Only one mapping is allowed per key. In your "map2", the keys are "itemNo" and "availQty". So what is happening is that your for loop sets the values for the first entry, and then is overwriting them with the data from the second entry, which is why that is the only one you see. Look at Java - Map and Map - Java 8 for more info.
I don't understand why you are trying to put the data into a map, you could just put it straight into JSON with something like this:
JSONArray partialArticlesInfo = new JSONArray();
for (Map.Entry<String,String> entry : partialStockArticlesQtyMap.entrySet()) {
JSONObject stockEntry = new JSONObject();
stockEntry.put("itemNo", entry.getKey());
stockEntry.put("availQty", entry.getValue());
partialArticlesInfo.put(stockEntry);
}
JSONObject root = new JSONObject();
root.put("partialArticlesInfo",partialArticlesInfo);
This will take "map1" (partialStockArticlesQtyMap in your code) and create a JSON object exactly like your example - no need to have map2 as an intermediate step. It loops over each entry in map1, creates a JSON object representing it and adds it to a JSON array, which is finally added to a root JSON object as "partialArticlesInfo".
The exact code may be slightly different depending on which JSON library you are using - check the docs for the specifics.
I agree with Brendan. Another solution would be otherwise to store in the Set or List objects like the following.
class Item {
Long itemNo;
int quantity;
public int hashCode() {
Long.hashCode(itemNo) + Integer.hashCode(quantity);
}
public int equals(Object other) {
other instanceOf Item && other.itemNo == this.itemNo && other.quantity = this.quantity;
}
}
}
then you can use the JsonArray method described by him to get the Json string in output
This means that adding new variables to the object won't require any more effort to generate the Json
I have a cache that looks like this:
Key: UUID
Value: Array[Long]
I want to get the key corresponding to a specific value. How does the where-part look like?
I have tried "value = ?" and "_value = ?" but these obviously doesnt work.
Yo!
What do you mean by Array[Long]? Is it just long[] or may be you are using Scala?
The simplest (but not the most effective) way would be using a scan query with predicate (docs here).
To achieve the best performance it is preferable to have your value indexed, so I'd recommend to have a special wrapper class for your array like this:
class MyArray implements Comparable<MyArray>, Serializable {
private long[] arr;
// implement compareTo,hashCode,equals
#GridCacheQuerySqlField(index = true)
public MyArray indexedArray() {
return this;
}
}
then the query will look like
"indexedArray = ?"
where as parameter you have to pass MyArray instance. It is a bit dirty way to index value but this is the only way right now.
By the way column names for cache key and value in SQL are _key and _val but not _value and you can write queries like
"_val = ? and _key > ?"
of course you have to make sure that your key and value at least implement hashCode and equals correctly, implementing Comparable is preferable.
Using Automapper, how do you handle the mapping of a property value on an object to an instance of a string. Basically I have a list of Role objects and I want to use Automapper to map the content of each "name" property to a corresponding list of string (so I just end up with a list of strings). I'm sure it has an obvious answer, but I can't find the mapping that I need to add to "CreateMap" to get it to work.
An example of the relevant code is shown below:
public class Role
{
public Guid Id{get;set;}
public string Name{get;set;}
...
...
}
// What goes in here?
Mapper.CreateMap<Role, string>().ForMember(....);
var allRoles = Mapper.Map<IList<Role>, IList<string>>(roles);
I love Automapper (and use it in a number of projects), but wouldn't this be easier with a simple LINQ statement?
var allRoles = from r in roles select r.Name
The AutoMapper way of accomplishing this:
Mapper.CreateMap<Role, String>().ConvertUsing(r => r.Name);
My site is using Subsonic 2.2 on my site.
I have 1 weird situation where I need to run some ad-hoc SQL statements.
public IList<string> GetDistincList(string TableName, string FieldName)
{
string sqlToRun = string.Format("SELECT DISTINCT {0} FROM {1} ORDER BY {0}", FieldName, TableName);
Query query = new Query(TableName);
query.PleaseRunThis(sqlToRun);
query.ExecuteReader();
}
Can anyone help me here? As it appears, I just want to return a generic list of strings.
Thanks!
Subsonic has a great method called ExecuteTypedList() so you can do somethink like this.
List<int> result = DB.Select(Table.Columns.Id)
.Distinct()
.From<Table>()
.OrderBy(Table.Columns.Id)
.ExecuteTypedList<int>();
or even with pocos:
public class UserResult
{
public int Id {get;set;}
public string Name {get;set;}
}
List<UserResult> users = DB.Select(
User.Columns.UserId + " as Id", // the as ... is only needed if your
User.Columns.UserName + " as Name" // column name differs from the
).From<User>() // property name of your class
.ExecuteTypedList<UserResult>();
Unfortunately this method doesn't work for string since it requires
a) a valuetype
b) a class with a parameterless constructor since the method uses reflection to map the columns from the result to the properties of the class
However I wrote an extension method a while ago that works for string:
Use the Subsonic.Select() ExecuteTypedList Method with String
Look at my own answer in the link.
If you add the extensionmethod to your code you can do:
List<String> result = DB.Select(User.Columns.UserName)
.From<User>()
.ExecuteTypedList();
Use the CodingHorror class.
Here's the SubSonic 3 way of doing it: http://www.subsonicproject.com/docs/CodingHorror
The SubSonic 2 way is similar:
Dim ch As SubSonic.CodingHorror
ch.Execute("delete from #tablename", table)