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sql_analysis [2010/09/25 01:30] danielsql_analysis [2016/10/04 16:17] – [Duplicate messages] daniel
Line 8: Line 8:
 FROM header, (values ('X-Priority'), ('Importance'), ('Precedence'), ('Priority'), ('X-MSMail-Priority'), ('X-MS-Priority')) as h(field) FROM header, (values ('X-Priority'), ('Importance'), ('Precedence'), ('Priority'), ('X-MSMail-Priority'), ('X-MS-Priority')) as h(field)
 WHERE position(E'\n'||field IN lines)>0 WHERE position(E'\n'||field IN lines)>0
-group by split_part(substr(lines, 1+position(E'\n'||field in lines), 200), E'\n', 1)+group by 1
 </code> </code>
  
Line 48: Line 48:
  X-Priority: Normal        |     5  X-Priority: Normal        |     5
 </code> </code>
 +
 +This alternative implementation uses regular expressions and differs in that it doesn't limit header values to 200 characters or any other fixed length.
 +<code sql>
 +select FIELD||':'||arr[1], count(*)
 + from (select FIELD, regexp_matches(lines, '(?:^|\n)' || FIELD || ':\s*([^\n]*)\n', 'g') as arr
 +       from header, 
 +         (VALUES ('X-Priority'), ('Importance'), ('Precedence'), ('Priority'),
 +             ('X-MSMail-Priority'), ('X-MS-Priority')) AS h(FIELD)
 +             where strpos(lines,FIELD)>0) l
 +GROUP BY 1 ORDER BY 1
 +</code>
 +
 +In this version, the '' strpos(lines,FIELD)>0 '' condition is not essential: it's introduced only as a first-pass filter to eliminate the headers that don't contain anywhere any of the searched fields.
 ====== Duplicate messages ====== ====== Duplicate messages ======
 This query finds each message that share the exact same headers than another message with a lower mail_id, which means that it's a duplicate. This query finds each message that share the exact same headers than another message with a lower mail_id, which means that it's a duplicate.
Line 53: Line 66:
 select h1.mail_id from header h1, header h2 where h1.lines=h2.lines and h1.mail_id > h2.mail_id select h1.mail_id from header h1, header h2 where h1.lines=h2.lines and h1.mail_id > h2.mail_id
 </code> </code>
 +
 +A stricter version, comparing the md5 hashes of bodies (text and html parts) in addition to the headers:
 +<code sql>
 +select b2.mail_id from body b1, body b2, header h1, header h2
 + where b1.mail_id < b2.mail_id
 + and h1.mail_id = b1.mail_id
 + and h2.mail_id = b2.mail_id
 + and md5(h1.lines) = md5(h2.lines)
 + and md5(b1.bodytext) is not distinct from md5(b2.bodytext)
 + and md5(b1.bodyhtml) is not distinct from md5(b2.bodyhtml);
 +</code>
 +
 +The ''IS NOT DISTINCT'' comparator behaves as expected when ''bodytext'' or ''bodyhtml'' is NULL, as opposed
 +to the simple equality operator, for which ''NULL=NULL'' is false
 +====== Messages with specific attachment types ======
 +To retrieve all messages containing pdf files or any image file:
 +<code sql>
 +select distinct mail_id FROM attachments WHERE content_type='application/pdf' OR content_type like 'image/%';
 +</code>
 +
 +====== Messages sent or received today  ======
 +<code>
 +select mail_id from mail where msg_date>=date_trunc('day',now());
 +</code>
 +
  
sql_analysis.txt · Last modified: 2019/01/24 17:55 by daniel