Querying Channels

LAST EDIT May 07 2021

Querying Channels

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It is necessary for most applications to query the API for channels. This will retrieve a list of channels and render them in a visual list in the application. Watching channels is the process by which a user can receive real-time updates on a channel with the Stream Chat API.

Here are some tips:

  • A channel is not created in the API until one of the following methods is used on the channel instance. Each method is subtly different.

Only one of these is necessary. For example, it is redundant to create a channel, if you also intend to watch that channel. The watch call automatically creates the channel in addition to watching the channel for real-time updates.

  • With client.queryChannels();, a user can watch up to 25 channels in a single API call, meaning there is no need to watch them individually or use channel.watch(); after queryChannels. Using client.queryChannels();can substantially decrease the API calls the application has to make, reducing network traffic and improving the performance of the application when watching many channels at once.

queryChannels filters

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A channel list in an application can often form the backbone of the chat experience and be one of the first views that a user sees upon opening a chat experience. As such, it is important to run an optimal filter to retrieve the channel list when needed.

A good guide is to use a filter that is as selective as possible. For example, if your filter is still going to return >50% of channels in the application, it may be problematic.

  • Avoid NOR logical operators and NIN and NOT comparison operators in the filter variable as they are not selective.

  • Filter by CID is the most performant query you can use.

  • For social messaging (DM’s, group chats, etc.), a minimum filter of type and members: {$in: userID} should be used.

  • Avoid overly complex queries that have >1 AND or OR statements.

  • Use custom fields on channels to make filters more simple.

  • Reach out to support@getstream.io if you plan on having millions of channels and are unsure of your queryChannels filter. We're here to help!

  • Filtering by type + channel_id is not recommended. Instead, use CID.

  • Filtering by type alone is not recommended. Instead, use CID.

Using CID is always more performant than ID.

queryChannels sort

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  • It is always best to use a sort parameter in the query, although we will default to updated_at. This is the more recent timestamp between Channel.create_at and Channel.last_message_at.

  • The other sort parameter that is highly optimized is last_message_at.

Sorting on custom fields is possible, but it does have some scalability implications. Sorting on a custom field is going to be performant up to ~2000-3000 channels. However, for Enterprise customers, this is possible for us to provide optimizations here in certain circumstances.

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