[Mailman-Developers] [CLI Project] Support of filtering of objects in Command Shell

[Rajeev S]

Hi,

Now the mid term evaluations are done, I would be building the command 
line shell, as planned. I would like to present how I would like to 
tackle the requirement at hand.

As mentioned in my proposal and the most logical approach, all the 
common functionalities between the shell and the already built command 
line tools would use the same classes, the ones built for the command tools.

As this is a command shell, I wish to give it a SQL like feel. However, 
The SQL commands SELECT, INSERT INTO do not look nice in Mailman 
context, as we are dealing with objects and not tables. I would be using 
the object related terms like SHOW, CREATE etc for the respective actions.

However, I would like to discuss about the support for the WHERE clause 
by the shell.

The WHERE clause is not mentioned in my proposal, but I feel that this 
feature ought to be in the project.

If the commands require to support a WHERE clause, as SQL does,

For example,

 >>> show users where display_name = 'foo' and subscribed_list_ids 
contains = 'list at domain.org <mailto:%27list at domain.org>'

The steps involved in processing a command with a WHERE clause would be


1.Parse the command
2.Filter the results from the database
3.Perform the action using the command line tool methods if possible 
else write a new procedure.

For the Step 2, there are two approaches in hand:

1.Use the Storm library to query the database directly, as mailman core 
does.
2.Use the REST API

By using the first approach, a good performance improvement is achieved, 
by leaving the data filtering to database engine. But this limits the 
usability of of the CLI to the system in which the mailman database 
exists, as the remote connections to DB servers are usually disabled.

By using the second approach, the performance is bad, as it requires a 
normal python `for` loop that compares the the results one by one. 
However, this approach might be easier in case that the mailman 
installation be managed remotely, if its OK to enable the REST API to 
accept connections from remote machines.(I believe this is currently not 
supported/disabled by default.)

By building the WHERE clause, its costlier to reuse the command line 
tools methods in many use cases, like delete, subscribe etc. Further, as 
I have already mentioned to Abhilash, it demands more time. I am not 
sure if that will fit into GSoC time frame. I am confident that I can 
make significant progress, but not sure if it can be 'completed'. Also, 
I am fine on completing it even after GSoC.

So, the final question is, Should the CLI support filtering using the 
WHERE clause? Or should I proceed as per my proposal, building a basic 
Mailman shell and leave the rest to be completed in future?