Long qery time in mod ...

[Demux]

Hello,

I have a problem with a execution time of a mod (add-on) from VBherald. If I open the script it takes many minutes for loading the pages. My "slowlog" says this:

# Query_time: 385 Lock_time: 0 Rows_sent: 0 Rows_examined: 1711866
SELECT p.vbheraldconversation as converse, p.threadid, t.title, t.threadid as tid, t.dateline
FROM vb3_thread t
LEFT JOIN vb3_post as p ON(t.threadid = p.threadid)
WHERE p.vbheraldconversation = 1 GROUP BY t.threadid ORDER BY t.dateline DESC LIMIT 10;

The support from the software told me that it works perfect on "small" boards. Can someone please take a look on this query to tell me what is wrong here? The row "vbheraldconversation" is always "0". Is it true that this query open every row of the table to make a check for every single post? Can this be the result of 385 seconds lookup time?

thanks for help ...