Loading a single item from a dynamic cache key

Introduction

This approach assumes that the cache to be loaded was added with a payload variable for the cache key, and is comprised of multiple, single-record payloads (having been through a flow control shape).

Each of these payloads has its own, unique cache key (when data was added to the cache, this key was generated dynamically by resolving a cache key payload variable).

For more information about this stage, please see Generating dynamic cache keys with payload variables.

When we come to load this data, we must target the required cache key. If you only want a single item, the quickest way is to specify the resolved cache key.

How it works

The load from cache shape works as normal - you choose the cache and cache key to be loaded:

However, the important point to consider is that the cache key that you specify here will have been generated dynamically by resolving the payload variable that was specified when the cache was added.

Example

Consider the following process flow:

Here, our manual payload contains customer data as below:

[
    {
        "id": 1000000001,
        "first_name": "Jane",
        "last_name": "Smith",
        "items": {
           "itemref": "0000001",
            "item1": "apples",
            "item2": "oranges",
            "item3": "pears"
        }
    },
    {
        "id": 1000000002,
        "first_name": "George",
        "last_name": "Jones",
        "items": {
           "itemref": "0000002",
            "item1": "tangerines",
            "item2": "peaches",
            "item3": "grapes"
        }
    },
    {
        "id": 1000000003,
        "first_name": "Bob",
        "last_name": "Brown",
        "items": {
           "itemref": "0000003",
            "item1": "nectarines",
            "item2": "raspberries",
            "item3": "strawberries"
        }
    },
    {
        "id": 1000000004,
        "first_name": "Marjorie",
        "last_name": "Simpson",
        "items": {
           "itemref": "0000004",
            "item1": "blueberries",
            "item2": "cranberries",
            "item3": "apricots"
        }
    }
]

To allow us to target specific customer records from this payload, we send it through a flow control shape, which is set to creating one payload for customer:

...so now we have lots of payloads to be cached:

If we look at the payload for the first of these, we can see it contains a single customer record - notice that there's an id field with a value of 1000000001. This field uniquely identifies each record.

Next we define an add to cache shape - we create a new cache and use a payload variable to generate a dynamic cache key for each incoming payload:

Here, they payload variable is defined as:

customer-[[payload.0.id]]

where:

• customer- is static text to prefix the resolved variable.

• [[payload.]] instructs the shape that this variable should be resolved from the incoming payload.

• 0 denotes that the first occurrence of the following item found in the payload should be used to resolve this variable.

• id is the name of the field in the payload to be used to resolve this variable

So, if we take our first payload above:

...our payload variable would resolve to the following cache key:

customer-1000000001

This is what we use in our load from cache shape: