I want to have a column of type string that will be composed of static prefix and dynamic auto incremented integer. Number should autoincrement on every insert. This column is not PK but it should act like id. Also i would like to filter on that column.
Something like
PREFIX_0000
PREFIX_0001
PREFIX_0002
PREFIX_0003
I don't want to store a counter in some table.
Is there a possibility to do that on NHibernate mapping level? Or any other ideas?
Thanks.
in you DTO you can make a getter which returns a prefix_######ID:
public string MyAutoIncrement
{
get { return string.Format("{0}_{1:D8}",this.Prefix,this.Id); }
}
Related
I have two classes.
class A {
String aName;
B b;
public A(String aName, B b) {
this.aName = aName;
this.b = b;
}
public String getaName() {
return aName;
}
public B getB() {
return b;
}
}
class B {
String bName;
public B(String bName) {
this.bName = bName;
}
public String getbName() {
return bName;
}
}
I am storing A as a set in Aerospike and A.aName is primary key. I want a secondary key on A.b. I have created index on A.b attribute and able to persist also. But search from the index is not returning anything. As per my understanding, Aerospike supports only three type of indexes: String, Numeric and Geo,. Is there any option for custom object.
Actually you can also index string, numeric and geo within different source types - basic (meaning just a bin with scalar data), list (so you can index strings or numeric data that is contained in a list), map keys and map values.
See: https://www.aerospike.com/docs/guide/query.html#secondary-index-key-source-type
You could model this in a few ways:
As a map. Let's assume that you store the value of A in a bin whose type is a map, it could have two map-keys - aName and bName. You can build a secondary index for string data on map values. Now, if you search for a specific bName you'll have this record come up.
More rationally you'd do the following as separate bins.
Assume that you use several bins, among them two bins to hold aname and bname. Their values are strings. You could now build a secondary index for string values and a basic index type (string data not contained in a complex data type such as list or map). You'd query for all the records where the predicate is bname = foo.
For a more complex situation one or more bname values map to a single aname, you'd actually model this as a lookup table.
Assume a set (table) called users holding records whose keys are the aname. A single key-value operation such as a read or an upsert works on a specific instance of class A, identified by a given aname. One record in Aerospike per instance of A.
You have another set (table) as the lookup table, where for each unique bname you create a record. The specific bname is the key to this record. The value is the aname. So to find the record in the users set, you first look it up in the lookup table by the bname. You use the value of this record as the key for the users record for that aname. This is the most common way of modeling this type of use case, without a secondary index.
Here is the answer post on Aerospike forum.
Binary blobs can be anything, there’s definitely no way to index that. If there is a particular field in your class you can pull out and set as a separate bin with a string/long type then that would work
https://discuss.aerospike.com/t/secondary-index-on-custom-java-object/6485
I am using Maps in my code for the first time, hence require some inputs from you experts.
My requirement is I have to check two different tables from database. Value from First table will be used as Key and Value for second table will be used as Value for the key.
Each key will have multiple values, so I will be storing all values against each key in a arraylist i.e. my Map will be like MAP.
Now, my issue is following:
I don't know the total no. of keys, so I can't create arraylist objects in advance. How to manage this?
How can I check if key exists in map such that if it exists then I have to updated the arraylist corresponding to it only. And if it doesn't exist then create new key, create arraylist corresponding to it, populate arraylist with the value.
Finally I have to iterate whole map and use the key and values.
How can it be implemented? Am I following the right approach? if not what is a better approach?
Thanks
With lists in Java you do not need to know the size up front. That is a requirement for Arrays. Therefore just create your Map
Map> myMap = new HashMap<>();
This should work
if (myMap.containsKey(someKey)) {
myMap.get(someKey).add(someValue); // adds a value to the list that already is in the map
} else {
myMap.put(someKey, Arrays.asList(someValue)); // which inserts a new key/value
}
If you need to iterate over all values in the list then you need a nested for loop
for (Map.Entry> entry : myMap.entrySet()) {
// your key = entry.getKey()
for (ValueType value : entry.getValue()) {
// use your value
}
}
http://docs.oracle.com/javase/7/docs/api/java/util/Map.html
Hope that helps.
Is it possible to configure NHibernate (specifically Fluent NHibernate) to serialize an array of simple types to a single database column? I seem to remember that this was possible but its been a while since I've used NHibernate.
Essentially I need to store the days of week that a person works (int[]) and would rather not have a separate table just for this purpose.
It is possible.
You need to implement a IUserType that takes care of mapping between your array and a data column (google that first; it's possible that somebody already implemented it)
Alternatively, you can do the conversion in your entity class, and map the single-field representation instead of the property. For example:
string numbers;
public int[] Numbers
{
get { return numbers.Split(','); }
set { numbers = string.Join(",", value.Select(x => x.ToString())); }
}
Yes. There's UserType for scenarios like that. You could also use enum and bit flag.
I'm mapping a view using ActiveRecord, which means I need a primary key. I don't have one, so I'm using ROW_NUMBER() to create one in the view definition to placate the system. However, I don't seem to know how to map it properly. I'm getting:
Could not find field 'stupidID' in class 'blah_blah'
NHibernate.PropertyNotFoundException: Could not find field 'stupidID' in class 'blah_blah'
My mapping looks like this. There is no
public long? stupidID;
[PrimaryKey("StupidId", Access = PropertyAccess.NosetterLowercaseUnderscore)]
public long? StupidId
{
get { return stupidID; }
}
Can anyone see what I'm missing?
NosetterLowercaseUnderscore means that by convention a prefix '_' is used and it's lowercase, so the field should be called _stupidid instead of stupidID.
Also, the PK shouldn't be a nullable type. I'd use long instead of long?
I have an entity, with a field of type enum, that is persisted as an integer in my database.
When retrieving objects from the database using ICriteria, I wish to restrict the results to those with the field being a member of a collection of enum values. Does Restrictions.In work with a collection of enums?
The following does not work. Do I have to perform something like type-casting at the "restrictions.in" part of the query?
var myEnumCollection = new MyEnum[] { MyEnum.One };
return FindAll<MyType>(Restrictions.In("EnumProperty", myEnumCollection));
FindAll is a method encapsulating
criteria.GetExecutableCriteria(Session).List<MyType>()
My initial guess would be that you'll need to compare against the integer values of the enum members (assuming that you're mapping the enum as an integer); so something like:
var myEnumCollection = new int[] { MyEnum.One };
return FindAll<MyType>(Restrictions.In("EnumProperty", myEnumCollection));
May be the solution that you're after. If you update your post with further details (mapping of the enum member and the sql being generated by the query), I may be able to provide further assistance.