Allow Alias to be Created on Source Bucket

It looks to me that with a recent change, a Developer cannot create Alias for Source Buckets. This is different from my understanding wherein we earlier agreed that we do not allow source bucket to be mutated at all – either at deployment or at runtime.

The decision to not allow Alias for source bucket is a problem because:

1. Now, source bucket cannot be accessed AT ALL. Which means, no lookups or any operation on other docs from the source bucket could be done.
2. Timers are of no use with this decision, as Source bucket cannot be lookedup; which means the TTL usecase (which is one of the Primary usecases) cannot be implemented.

What I recommend:

1. Allow Alias to be created for Source Bucket. Also, Timers mutate the source bucket docs for they to work; and we continue to suppress the mutations out of it. QE and Perf tests have been running with this for a few months now and no issues have been reported so far. QE already had the tests for testing source bucket mutations and they can include them back, if we support this.
2. Gautham suggested that : we throw an exception if source bucket is tried to be modified – but this can happen only at runtime and not at deployment time. Am fine with this as a last resort(though its not elegant), but because of the rational with #1, I would say, this case need not be considered.

From Siri: Yes, I'm in agreement with what you write below. We should allow reading (and SELECT) of source bucket. It's only writing or UPDATE them that are problematic. I can also understand Gautham's issue that it's not easy to detect if something is used for read or write until runtime. For vulcan, please enforce it at runtime.

MB-27268 will track the changes for allowing source bucket updates from the Function.