I’ve just finished migrating all the comments of this blog from WordPress to Disqus. Why using an external comment platform? It’s just that I plan to ditch WordPress entirely, and switch to a static site generator in the near future. Here are some details on my migration to Disqus.

Disqus has everything you need to easily import WordPress comments. But first, I had to massage some data.

Articles of this blog features a lots of code. Comments are no exception and embed snippets too. Code blocks are rendered by the SyntaxHighlighter Evolved WordPress plugin. This extension use square brackets to enclose code. Disqus uses standard HTML tags.

Let’s update this notation directly in WordPress database:

$ mysqldump --opt kevblog wp_comments > ./comments.sql
$ perl -pe 's/\[code lang=(.*?)\]/<pre><code class=\1>/g' ./comments.sql > comments-fixed.sql
$ sed -i 's/\[\/code\]/<\/code><\/pre>/g' ./comments-fixed.sql
$ mysql kevblog < ./comments-fixed.sql

Disqus doesn’t support HTML lists. So I manually updated WordPress comments to remove occurrences of <ul> and <ol>, and replace <li> by an UTF-8 bullet.

Another issue: if Disqus support images in comment, in imported comments they are left as HTML tags and therefore not rendered by Disqus. I was the only one on my blog posting images in comments. So I simply moved them to the corresponding parent article.

I then had to fix the comment threading. In the first versions of WordPress, sub-commenting was not supported. I addressed this issue by recomposing threading with a series of MySQL queries:

UPDATE `wp_comments` SET `comment_parent` = 234   WHERE `comment_ID` = 342;
UPDATE `wp_comments` SET `comment_parent` = 4987  WHERE `comment_ID` = 5667;
UPDATE `wp_comments` SET `comment_parent` = 10915 WHERE `comment_ID` = 10916;

After all these updates, my comments where ready to be exported to Disqus.

If most of my comments were successfully imported, some were left-out. The importer was not able to find their parents:

Disqus comment import: unable to find parent

But the reported error was not true: parent’s IDs were good and referenced an existing comment. Besides, comments Disqus was not able to import were correctly placed in their thread on my original WordPress blog.

For a moment I trough Disqus import code was subject to a race condition. But there was no <wp:comment_parent /> tags in my XML file.

I also checked that no comment were moderated:

$ grep -c "<wp:comment_approved>0</wp:comment_approved>" ./kevindeldycke.wordpress.2013-01-15-fixed.xml
$ grep -c "<wp:comment_approved>1</wp:comment_approved>" ./kevindeldycke.wordpress.2013-01-15-fixed.xml

I decided to check the comments carefully. Following the chain of comment’s parents, I found the root cause. All unimported comments were descendants of an anonymous commenter. These shared the following empty properties:


I then decided to forced anonymous comments to bear a generic author’s name:

$ perl -0p -e 's/(<wp:comment_author><!\[CDATA\[)(\]\]><\/wp:comment_author>\s*<wp:comment_author_email><\/wp:comment_author_email>)/\1Anonymous\2/sg' ./kevindeldycke.wordpress.2013-01-15-fixed.xml > test.xml

Resulting in the following changes:

--- ./kevindeldycke.wordpress.2013-01-15-disqus-import-fixed.xml        2013-01-15 11:24:06.929837283 +0100
+++ ./test.xml  2013-01-27 16:19:00.062626017 +0100
@@ -6595,7 +6595,7 @@
-     <wp:comment_author><![CDATA[]]></wp:comment_author>
+     <wp:comment_author><![CDATA[Anonymous]]></wp:comment_author>
@@ -8376,7 +8376,7 @@
-     <wp:comment_author><![CDATA[]]></wp:comment_author>
+     <wp:comment_author><![CDATA[Anonymous]]></wp:comment_author>

I then sent the fixed WordPress XML export to Disqus as-is, which imported my 24 missing comments:

Disqus comment import: missing comments

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