We should probably have somewhere with general guidance on what we consider to be an 'excessive' number of channels for a single document, and suggestions for grouping these channels up into roles to reduce the overhead on a single document.
Currently when using convergence, we have a hard limit of 1MB of metadata.
A very rough estimate can be calculated with the following formula:
max channels per doc = 1MB xattrs limit / ( average channel name size * revs_limit )**
Given an average channel name size of 25 bytes, and 1MB of xattrs... we get:
revs_limit=1000: ~40 channels
revs_limit=100: ~400 channels
With non-convergence, the limit is more lax, but it eats into the 20MB doc size instead. Larger documents have less room for large numbers of channels.
max channels per doc = (20MB doc limit - doc size) / ( average channel name size * revs_limit )
Given the same criteria, but also a 5MB doc body, we'll get:
revs_limit=1000: ~600 channels
revs_limit=100: ~6,000 channels
There is definitely scope for optimizing how we store channel data in a document's metadata, especially for the case of xattrs where space is a premium, but I think it's still good to get a rough guide up somewhere.