May 13, 2010 Define the partitioning key. The partitioning key is defined using the DISTRIBUTED BY HASH clause in the CREATE TABLE command. After the partition key is defined, it cannot be altered. The only way to change it is to recreate the table. Subject: Re: abinitio-l Surrogate key generation process To: gops1034 Posted by Lourdes Manickam on Apr 22 at 1:03 AM Logically it should work, not sure where it is snaping. After creating the lookup, are you able to view the data? You can try this for surrogate keys while running in parallel.
A key serves as a unique identifier for each entity instance. Most entities in EF have a single key, which maps to the concept of a primary key in relational databases (for entities without keys, see Keyless entities). Entities can have additional keys beyond the primary key (see Alternate Keys for more information).
By convention, a property named
Id or <type name>Id will be configured as the primary key of an entity.
Note
Owned entity types use different rules to define keys.
You can configure a single property to be the primary key of an entity as follows:
You can also configure multiple properties to be the key of an entity - this is known as a composite key. Composite keys can only be configured using the Fluent API; conventions will never setup a composite key, and you can not use Data Annotations to configure one.
Primary key name
By convention, on relational databases primary keys are created with the name
PK_<type name> . You can configure the name of the primary key constraint as follows:
Key types and values
While EF Core supports using properties of any primitive type as the primary key, including
string , Guid , byte[] and others, not all databases support all types as keys. In some cases the key values can be converted to a supported type automatically, otherwise the conversion should be specified manually.
Key properties must always have a non-default value when adding a new entity to the context, but some types will be generated by the database. In that case EF will try to generate a temporary value when the entity is added for tracking purposes. After SaveChanges is called the temporary value will be replaced by the value generated by the database.
Important
If a key property has its value generated by the database and a non-default value is specified when an entity is added, then EF will assume that the entity already exists in the database and will try to update it instead of inserting a new one. To avoid this turn off value generation or see how to specify explicit values for generated properties.
Alternate Keys
An alternate key serves as an alternate unique identifier for each entity instance in addition to the primary key; it can be used as the target of a relationship. When using a relational database this maps to the concept of a unique index/constraint on the alternate key column(s) and one or more foreign key constraints that reference the column(s).
Tip
If you just want to enforce uniqueness on a column, define a unique index rather than an alternate key (see Indexes). In EF, alternate keys are read-only and provide additional semantics over unique indexes because they can be used as the target of a foreign key.
Alternate keys are typically introduced for you when needed and you do not need to manually configure them. By convention, an alternate key is introduced for you when you identify a property which isn't the primary key as the target of a relationship.
You can also configure a single property to be an alternate key:
You can also configure multiple properties to be an alternate key (known as a composite alternate key): Macromedia dreamweaver 8 key generator tutorial.
Finally, by convention, the index and constraint that are introduced for an alternate key will be named -->
AK_<type name>_<property name> (for composite alternate keys <property name> becomes an underscore separated list of property names). You can configure the name of the alternate key's index and unique constraint:
This article discusses some common scenarios in writing code using Azure Event Hubs. It assumes a preliminary understanding of Event Hubs. For a conceptual overview of Event Hubs, see the Event Hubs overview.
Warning
This guide is for the old Microsoft.Azure.EventHubs package. We recommend that you migrate your code to use the latest Azure.Messaging.EventHubs package.
Event publishers
You send events to an event hub either using HTTP POST or via an AMQP 1.0 connection. The choice of which to use and when depends on the specific scenario being addressed. AMQP 1.0 connections are metered as brokered connections in Service Bus and are more appropriate in scenarios with frequent higher message volumes and lower latency requirements, as they provide a persistent messaging channel.
When using the .NET managed APIs, the primary constructs for publishing data to Event Hubs are the EventHubClient and EventData classes. EventHubClient provides the AMQP communication channel over which events are sent to the event hub. The EventData class represents an event, and is used to publish messages to an event hub. This class includes the body, some metadata(Properties), and header information(SystemProperties) about the event. Drivers nand x windows 8. Other properties are added to the EventData object as it passes through an event hub.
Get started
The .NET classes that support Event Hubs are provided in the Microsoft.Azure.EventHubs NuGet package. You can install using the Visual Studio Solution explorer, or the Package Manager Console in Visual Studio. To do so, issue the following command in the Package Manager Console window:
Create an event hub
You can use the Azure portal, Azure PowerShell, or Azure CLI to create Event Hubs. For details, see Create an Event Hubs namespace and an event hub using the Azure portal.
Create an Event Hubs client
The primary class for interacting with Event Hubs is Microsoft.Azure.EventHubs.EventHubClient. You can instantiate this class using the CreateFromConnectionString method, as shown in the following example:
Send events to an event hub
You send events to an event hub by creating an EventHubClient instance and sending it asynchronously via the SendAsync method. This method takes a single EventData instance parameter and asynchronously sends it to an event hub.
Event serialization
The EventData class has two overloaded constructors that take a variety of parameters, bytes or a byte array, that represent the event data payload. When using JSON with EventData, you can use Encoding.UTF8.GetBytes() to retrieve the byte array for a JSON-encoded string. For example:
Partition key
Note
If you aren't familiar with partitions, see this article.
When sending event data, you can specify a value that is hashed to produce a partition assignment. You specify the partition using the PartitionSender.PartitionID property. However, the decision to use partitions implies a choice between availability and consistency.
Availability considerations
https://brownflight683.weebly.com/farming-simulator-2011-product-key-generator.html. Using a partition key is optional, and you should consider carefully whether or not to use one. If you don't specify a partition key when publishing an event, a round-robin assignment is used. In many cases, using a partition key is a good choice if event ordering is important. When you use a partition key, these partitions require availability on a single node, and outages can occur over time; for example, when compute nodes reboot and patch. As such, if you set a partition ID and that partition becomes unavailable for some reason, an attempt to access the data in that partition will fail. If high availability is most important, do not specify a partition key; in that case events are sent to partitions using the round-robin model described previously. In this scenario, you are making an explicit choice between availability (no partition ID) and consistency (pinning events to a partition ID).
Another consideration is handling delays in processing events. In some cases, it might be better to drop data and retry than to try to keep up with processing, which can potentially cause further downstream processing delays. For example, with a stock ticker it's better to wait for complete up-to-date data, but in a live chat or VOIP scenario you'd rather have the data quickly, even if it isn't complete.
https://brownflight683.weebly.com/chance-of-ever-generating-same-key-twice-10-letters.html. Given these availability considerations, in these scenarios you might choose one of the following error handling strategies:
https://potentgsm.weebly.com/free-vpn-app-mac-os.html. Download crack video studio 12. For more information and a discussion about the trade-offs between availability and consistency, see Availability and consistency in Event Hubs.
Batch event send operations
Sending events in batches can help increase throughput. You can use the CreateBatch API to create a batch to which data objects can later be added for a SendAsync call.
A single batch must not exceed the 1 MB limit of an event. Additionally, each message in the batch uses the same publisher identity. It is the responsibility of the sender to ensure that the batch does not exceed the maximum event size. If it does, a client Send error is generated. You can use the helper method EventHubClient.CreateBatch to ensure that the batch does not exceed 1 MB. You get an empty EventDataBatch from the CreateBatch API and then use TryAdd to add events to construct the batch.
Key Generation While Using PartitionsSend asynchronously and send at scale
You send events to an event hub asynchronously. Sending asynchronously increases the rate at which a client is able to send events. SendAsync returns a Task object. You can use the RetryPolicy class on the client to control client retry options.
Event consumers
The EventProcessorHost class processes data from Event Hubs. You should use this implementation when building event readers on the .NET platform. EventProcessorHost provides a thread-safe, multi-process, safe runtime environment for event processor implementations that also provides checkpointing and partition lease management.
To use the EventProcessorHost class, you can implement IEventProcessor. This interface contains four methods:
To start event processing, instantiate EventProcessorHost, providing the appropriate parameters for your event hub. For example:
Note
EventProcessorHost and its related classes are provided in the Microsoft.Azure.EventHubs.Processor package. Add the package to your Visual Studio project by following instructions in this article or by issuing the following command in the Package Manager Console window:
Install-Package Microsoft.Azure.EventHubs.Processor .
Then, call RegisterEventProcessorAsync to register your IEventProcessor implementation with the runtime:
At this point, the host attempts to acquire a lease on every partition in the event hub using a 'greedy' algorithm. These leases last for a given timeframe and must then be renewed. As new nodes, worker instances in this case, come online, they place lease reservations and over time the load shifts between nodes as each attempts to acquire more leases.
Key Generation While Using Partition Key
Over time, an equilibrium is established. This dynamic capability enables CPU-based autoscaling to be applied to consumers for both scale-up and scale-down. Because Event Hubs does not have a direct concept of message counts, average CPU utilization is often the best mechanism to measure back end or consumer scale. If publishers begin to publish more events than consumers can process, the CPU increase on consumers can be used to cause an auto-scale on worker instance count.
The EventProcessorHost class also implements an Azure storage-based checkpointing mechanism. This mechanism stores the offset on a per partition basis, so that each consumer can determine what the last checkpoint from the previous consumer was. As partitions transition between nodes via leases, this is the synchronization mechanism that facilitates load shifting.
Key Generation While Using Partition MusicPublisher revocation
In addition to the advanced run-time features of Event Processor Host, the Event Hubs service enables publisher revocation in order to block specific publishers from sending event to an event hub. These features are useful if a publisher token has been compromised, or a software update is causing them to behave inappropriately. In these situations, the publisher's identity, which is part of their SAS token, can be blocked from publishing events.
Note
Currently, only REST API supports this feature (publisher revocation).
For more information about publisher revocation and how to send to Event Hubs as a publisher, see the Event Hubs Large Scale Secure Publishing sample.
Next steps
To learn more about Event Hubs scenarios, visit these links:
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