In GridGain, I have to load data such that the primary key is a composite key.
Say I have
class Person{
int id;
int officeId;
...
}
Here I want to add as primary key both id and officeId. Is it possible to add a composite key in GridGain?
in GridGain any Object can be used as a key, just like with HashMaps. You need to make sure that you override equals(...) and hashCode() methods for the composite keys.
Related
I have a table to create in cassandra with custom type.
From java project, I have this class :
public class Product {
#Column(value = "tags")
private List<String> tags;
#Column(value = "price")
private double price;
}
I want to create a user-type in cassandra with this class :
CREATE TYPE quangkeyspace.student (
tags list<text>,
price floats
);
But it has error when execute : InvalidRequest: Error from server: code=2200 [Invalid query] message="A user type cannot contain non-frozen UDTs"
How to solve this problem?
Depending on your Cassandra version, you may be required to define your UDT as frozen. This practically means that the field is immutable and that cassandra treats the field as a blob, preventing the modification of different fields inside of the type.
Also, keep in mind that Partition keys must always be frozen due to how tokens are hashed from the value of the key.
This might be doing what you want.
I'm reviewing Azure tables in an existing implementation. Here's an example of data from 1 row:
partitionkey (string):
6b348096-e6cb-4126-ba3c-cd0c9e8ba9c9
rowkey (string):
02519452888782521547_c1a98e0f-1b25-4d38-bd96-d72b30a97bf0
Obviously, rowkey does not have a proper guid and both column names are native to Azure and required per entity. There does not appear to be an identity or default insert for these columns. Can someone please provide context around these columns and the implementation style differences and considerations between these Azure columns vs a SQL Server style implementation?
I have no idea about how the partition key and row key are constructed in your table, please turn to someone who created the table. :)
About the considerations on the Azure Table design, you can refer to this post (which is very complete and helpful).
Partitionkey and Rowkey are just two properties of entitis in Azure table. Rowkey is the "primary key" within one partition. Within one PartitionKey, you can only have unique RowKeys. If you use multiple partitions, the same RowKey can be reused in every partition. PartitionKey + RowKey form the unique identifier(Primary key) for an entity.
In your table, the partitionkey and rowkey are just assigned with a random string. I'm not sure whether you designed this table or somebody else, but these two properties can be assigned with other values through Azure Storage .NET client libary and Rest API. As the example below, you can design the rowkey and partitionkey, and assign whatever valid value you want, here lastname for Partitionkey and firstname for rowkey:
public class CustomerEntity : TableEntity
{
public CustomerEntity(string lastName, string firstName)
{
this.PartitionKey = lastName;
this.RowKey = firstName;
}
public CustomerEntity() { }
public string Email { get; set; }
public string PhoneNumber { get; set; }
}
It’s better to think about both properties and your partitioning strategy. Don’t just assign them a guid or a random string as it does matter for performance. I recommend you go through Designing a Scalable Partitioning Strategy for Azure Table Storage, the most commom used is Range Partitions, but you can choose whatever you want.
This is a great blog help you understand how partitionkey and rowkey work http://blog.maartenballiauw.be/post/2012/10/08/What-PartitionKey-and-RowKey-are-for-in-Windows-Azure-Table-Storage.aspx
I am very new to Mybatis and stuck in a situation I have some questions
The complete scenario is I need to read and excel file and insert the excel data in database in two different tables having primary and foreign key relationship .
I am able to read the excel data and able to insert in primary table but not getting how to insert data in second table actually the problem is I have two different pojo classes having separate data for for each table two different mappers.
I am achiving association by defining the pojo of child table inside the pojo of parent class
Is there any way to insert data in two different table.
Is is possible to run 2 insert queries in single tag
Any help would be appreciable
There are lot of ways to do that.
Here is demonstration of one of the most straightforward ways to do that - using separate inserts. The exact solution may vary insignificantly depending mainly on whether primary keys are taken from excel or are generated during insertion into database. Here I suppose that keys are generated during insertion (as this is a slightly more complicated case)
Let's assume you have these POJOs:
class Parent {
private Integer id;
private Child child;
// other fields, getters, setters etc
}
class Child {
private Integer id;
private Parent parent;
// other fields, getters, setters etc
}
Then you define two methods in mapper:
public interface MyMapper {
#Insert("Insert into parent (id, field1, ...)
values (#{id}, #{field1}, ...)")
#Options(useGeneratedKeys = true, keyProperty = "id")
void createParent(Parent parent);
#Insert("Insert into child(id, parent_id, field1, ...)
values (#{id}, #{parent.id}, #{field1}, ...)")
#Options(useGeneratedKeys = true, keyProperty = "id")
void createChild(Child child);
}
and use them
MyMapper myMapper = createMapper();
Parent parent = getParent();
myMapper.createParent(parent);
myMapper.createChild(parent.getChild());
Instead of single child there can be a collection. In that case createChild is executed in the loop for every child.
In some databases (posgresql, sql server) you can insert into two tables in one statement. The query however will be more complex.
Another possibility is to use multiple insert statements in one mapper method. I used code similar to this in postgresql with mapping in xml:
<insert id="createParentWithChild">
insert into parent(id, field1, ...)
values (#{id}, #{field1}, ...);
insert into child(id, parent_id, field1, ...)
values (#{child.id}, #{id}, #{child.field1},...)
</insert>
and method definition in mapper interface:
void createParentWIthChild(Parent parent);
I know this is a little old, but the solution which worked best for me was implementing 2 insert stanzas in my mapping xml.
<insert id="createParent">
insert into parent(id, field1, ...)
values (#{id}, #{field1}, ...);
</insert>
<insert id="createChild">
insert into child(id, parent_id, field1, ...)
values (#{child.id}, #{id}, #{child.field1},...);
</insert>
And then chaining them. ( if the parent call failed do not continue to call the child)
As a side note, In my case I am using camel-mybatis so my camel-config had
<from uri="stream:in"/>
<to uri="mybatis:createParent?statementType=Insert"/>
<to uri="mybatis:createChild?statementType=Insert"/>
I would like to run the following code with a compound primary key.
Column<String> result = keyspace.prepareQuery(CF_COUNTER1)
.getKey(rowKey)
.getColumn("Column1")
.execute().getResult();
Long counterValue = result.getLongValue();
Research seems to show that it can be a string that represents a key (if it's not a compound primary key). The documentation says that it is of type K, alas, I am not very experience with Java, and have no idea what that means. Is it just a base type that lots of stuff inherits from? If so, I'm not really any closer to knowing what getKey(K) needs in order to handle a compound key (am I?).
You just need to write a class that fits the columns in your data model. You can then give this class to Astyanax in your mutations or queries.
For example, if you had a data model like this
CREATE TABLE fishblogs (
userid varchar,
when timestamp,
fishtype varchar,
blog varchar,
image blob,
PRIMARY KEY (userid, when, fishtype)
);
you would create a class like this:
public class FishBlog {
#Component(ordinal = 0)
public long when;
#Component(ordinal = 1)
public String fishtype;
#Component(ordinal = 2)
public String field;
public FishBlog() {
}
}
When and fishtype form your composite column key and are represented by the FishBlog class. Userid would be your row/partition key and can be of the simple "string" type.
Have a look at this blog explaining in great detail how to insert data with composite keys (where I took this example from).
Hope that helps.
how to get the primary key value after the tablename.Save() method
For Example:
Table.Save();
here how to my auto generated primary key value...
There's a couple of ways. You can just check the primary key property, so if you Table has an auto incrementing integer primary key you could do:
int primaryKeyValue = Table.Id;
Or you could use the KeyValue() method, which returns an object:
object primaryKeyValue = Table.KeyValue();