Percent of edit summaries with zero text

SQL

SELECT
    COUNT(CASE WHEN true_comment_length = 0 THEN 1 ELSE NULL END) AS zero_length_count,
    COUNT(*) AS total_count,
    COUNT(CASE WHEN true_comment_length = 0 THEN 1 ELSE NULL END) / COUNT(*) * 100 AS percent_zero_length
FROM
    (SELECT
        LENGTH(
            -- Remove /* */ comments from the comment_text
            REGEXP_REPLACE(cr.comment_text, '/\\*.*?\\*/', '') 
        ) AS true_comment_length
    FROM
        recentchanges rc
    JOIN
        comment_recentchanges cr ON rc.rc_comment_id = cr.comment_id
    WHERE
        rc.rc_bot <> 1 AND
        rc.rc_source = "mw.edit" AND
        NOT cr.comment_text LIKE 'Undid revision%' AND
        NOT cr.comment_text LIKE 'Restored revision%' AND
        NOT SUBSTRING(rc.rc_timestamp, 1, 8) = DATE_FORMAT(NOW(), '%Y%m%d')
	LIMIT 100000
    ) AS subquery;
SQL

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