Import comment cid and thread structure

Problem/Motivation

Currently, FeedsCommentProcessor.inc does not include a mapping target for the comment cid. I am in a situation that requires importing comments from another Drupal installation and preserving the comment thread structure. There is a mapping target for the comment parent (pid) but this is useless without also importing the comment cid.

I tried merely adding a mapper for cid, but that prevents any comments from being created because comment_save() assumes if the $comment object has the cid set that it is updating a record, not inserting one. It also does not populate the thread column in the comment table and loses the thread hierarchy structure.

Proposed resolution

This is not a perfect solution and is more of a work-around, proceed only if you know what you are doing.
I will attach my patch that adds a mapper for cid and thread. It also changes the entitySave() function to insert a comment record in the db table with the cid (in order to preserve the cid, as opposed to setting the cid based on the auto_increment).

Because the Drupal uses the auto_increment for the comment database table, I had set this auto_increment value to greater than any imported comments to avoid conflicts when comments are manually added after the import. I executed the following mysql statement: (replace 9999 with max + 1 of your imported comment cids)

ALTER TABLE `comment` AUTO_INCREMENT = 9999;

This requires your source has the thread data (column on the comments db table that is used to store the thread structure in van string format). In my case, I have a D6 site dumping the contents out with a view, in order to get the thread data I had to use the views_customfield module and used a customPHPfield to get this data:

<?php
$result = db_query("SELECT * FROM {comments} WHERE cid=%d", $data->cid);
$row = db_fetch_array($result);
print $row['thread']
?>

Remaining tasks

This is merely for discussion, it'd be a much more ambitious undertaking to try to preserve cid and thread structure without my work-around importing the thread data.

User interface changes

This adds mapping targets to the Comment Processor