Table of Contents

VisualQuery: In Streams

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DataSources often have In Streams. Some are required and some are optional. There are three common cases:

  1. No In-Streams because the DataSource generates data (eg. the Sql DataSource)
  2. In-Streams which supply data for processing
  3. In-Streams which simply supply configuration

The counterpart of In-Streams are Out-Streams.

This is what In-Streams look like in VisualQuery:

The Three Common Cases

Case 1: DataSources without In-Streams

Root DataSources generate or get data, and don't need an In-Stream. Here's an example from a CSV DataSource.

Case 2: In-Streams for Data Processing

This is a most common case, where a datasource gets one or more streams, and filter or modify the content. Here's an example of the StreamPick DataSource which has 3 inbound streams, and picks the one called Default to pass on:

Case 3: In-Streams for Configuration

In addition to data providing In-Streams, a DataSource may also use the data from an In to get a setting.

In these cases the first item in the stream can be used as a parameter in the Settings using In-Lookups like [In:Module:Category]. Read more about In-LookUps.

In-Stream Names

The names on an In-Stream are important since they affect how the stream is used.

Note that the names must be unique. This is case-insensitive, so Default and default are regarded as the same name and wouldn't be valid.

Pre-Named In-Streams

If the DataSource has special In-Streams which have a pre-defined purpose they are pre-named. This example of the ValueFilter DataSource can run a filter on Default, and if it ends up empty, can deliver a Fallback stream:

  1. The Country filter - it didn't find anything in the Default for the filter, so it receives 11 items and forwards 11 items from the Fallback
  2. Test data for Country is blank
  3. The Industry filter - it did find something, so it only forwards the 2 matching items
  4. Test data for the Industry expects Web

Dynamic In-Streams

Some DataSources can handle an infine amount of In-Streams like the StreamPick DataSource. This is indicated by the orange 🔺 on mouse-over:

This means you can connect as many In-Streams as you want. Just make sure the names are unique.

Rename In-Streams

You can always rename a connection by clicking on the name and typing in a new name.

Required vs. Optional In-Streams

Some streams are optional, some are required. In the example of the ValueFilter above, the Default is required, and the Fallback is optional.

In-Streams Cannot be Re-Used

An Out-Stream can be connected to multiple In-Streams but the opposite is not possible. So an In can only have one source, but an Out can give it's data to multiple In sources.

Nice to Know

  1. By convention, the default In-stream is called Default
  2. In-Streams have data which can be used, but they are not accessed until you really need them

History

  1. Introduced ca. in 2sxc 6
  2. Dynamic-In has existed since 2sxc 6 but the visual queue was added in 2sxc 11.13
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