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.
Related
I have the following udt type
CREATE TYPE tag_partitions(
year bigint,
month bigint);
and the following table
CREATE TABLE ${tableName} (
tag text,
partition_info set<FROZEN<tag_partitions>>,
PRIMARY KEY ((tag))
)
The table schema is mapped using the following model
case class TagPartitionsInfo(year:Long, month:Long)
case class TagPartitions(tag:String, partition_info:Set[TagPartitionsInfo])
I have written a function which should create an Update.IfExists query: But I don't know how I should update the udt value. I tried to use set but it isn't working.
def updateValues(tableName:String, model:TagPartitions, id:TagPartitionKeys):Update.IfExists = {
val partitionInfoType:UserType = session.getCluster().getMetadata
.getKeyspace("codingjedi").getUserType("tag_partitions")
//create value
//the logic below assumes that there is only one element in the set
val partitionsInfoSet:Set[UDTValue] = model.partition_info.map((partitionInfo:TagPartitionsInfo) =>{
partitionInfoType.newValue()
.setLong("year",partitionInfo.year)
.setLong("month",partitionInfo.month)
})
println("partition info converted to UDTValue: "+partitionsInfoSet)
QueryBuilder.update(tableName).
`with`(QueryBuilder.WHAT_TO_DO_HERE_TO_UPDATE_UDT("partition_info",partitionsInfoSet))
.where(QueryBuilder.eq("tag", id.tag)).ifExists()
}
The mistake was I was adding partitionsInfoSet in the table but it is a Set of Scala. I needed to convert into Set of Java using setAsJavaSet
QueryBuilder.update(tableName).`with`(QueryBuilder.set("partition_info",setAsJavaSet(partitionsInfoSet)))
.where(QueryBuilder.eq("tag", id.tag))
.ifExists()
}
Although, it didn't answer your exact question, wouldn't it be easier to use Object Mapper for this? Something like this (I didn't modify it heavily to match your code):
#UDT(name = "scala_udt")
case class UdtCaseClass(id: Integer, #(Field #field)(name = "t") text: String) {
def this() {
this(0, "")
}
}
#Table(name = "scala_test_udt")
case class TableObjectCaseClassWithUDT(#(PartitionKey #field) id: Integer,
udts: java.util.Set[UdtCaseClass]) {
def this() {
this(0, new java.util.HashSet[UdtCaseClass]())
}
}
and then just create case class and use mapper.save on it. (Also note that you need to use Java collections, until you're imported Scala codecs).
The primary reason for using Object Mapper could be ease of use, and also better performance, because it's using prepared statements under the hood, instead of built statements that are much less efficient.
You can find more information about Object Mapper + Scala in article that I wrote recently.
I have a case class which represents partition key values.
case class UserKeys (bucket:Int,
email: String)
I create query Clauses as follows:
def conditions(id: UserKeys):List[Clauses] = List(
QueryBuilder.eq("bucket", id.bucket), //TODOM - pick table description from config/env file.
QueryBuilder.eq("email", id.email)
)
And use the query as follows
val selectStmt =
select()
.from(tablename)
.where(QueryBuilder.eq(partitionKeyColumns(0), whereClauseList(0))).and(QueryBuilder.eq(partitionKeyColumns(1), whereClauseList(1)))
.limit(1)
I am getting following error.
com.datastax.driver.core.exceptions.InvalidTypeException: Value 0 of type class com.datastax.driver.core.querybuilder.Clause$SimpleClause does not correspond to any CQL3 type
Question 1 - What am I doing wrong?
The query works on cqlsh
The table I am querying is
CREATE TABLE users (
bucket int,
email text,
firstname text,
lastname text,
authprovider text,
password text,
PRIMARY KEY ((bucket, email), firstname, lastname)
Question 2 - Is there a way to print the List which contains the query clauses? I tried it but I get this incomprehensible text.
List(com.datastax.driver.core.querybuilder.Clause$SimpleClause#2389b3ee, com.datastax.driver.core.querybuilder.Clause$SimpleClause#927f81)
My bad, I was using the query clauses incorrectly. Rather than
.where(QueryBuilder.eq(partitionKeyColumns(0), whereClauseList(0))).and(QueryBuilder.eq(partitionKeyColumns(1), whereClauseList(1)))
I needed to do
.where(whereClauseList(0)).and(whereClauseList(1))
because the List already has QueryBuilder.eq("bucket", id.bucket) part
I am new to cassandra triggers. I am still ramping up. I could find a way to extract value out for a given ByteBuffer key, but do not know how to get the "name" of the actual primary key column
public static String getKeyText(ColumnFamily columnFamily, ByteBuffer key) {
CFMetaData cfm = columnFamily.metadata();
String key_data = cfm.getKeyValidator().getString(key);
}
Any idea on how to get just the key column name?
Any pointers are highly appreciated
Thanks
not sure if this what you mean, but you can get the name of the partition keys from columnFamily.partitionKeyColumns() the ColumnDefinition's have a name field thats readable. There may be more than one depending on schema
https://github.com/apache/cassandra/blob/cassandra-2.1/src/java/org/apache/cassandra/config/CFMetaData.java#L797
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
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.