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sql_analysis [2012/01/28 02:55] danielsql_analysis [2019/01/24 17:55] (current) – [Presence and count of specific mail headers] daniel
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 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>
  
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  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]*)', 'gi') 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.
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 </code> </code>
  
-====== Messages with specific attachment types ====== +A stricter version, comparing the md5 hashes of bodies (text and html parts) in addition to the headers:
-To retrieve all messages containing pdf files or any image file:+
 <code sql> <code sql>
-select distinct mail_id FROM attachments WHERE content_type='application/pdf' OR content_type like 'image/%';+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> </code>
  
-====== Messages sent or received today  ====== +The ''IS NOT DISTINCT'' comparator behaves as expected when ''bodytext'' or ''bodyhtml'' is NULL, as opposed 
-<code> +to the simple equality operator, for which ''NULL=NULL'' is false 
-select mail_id from mail where msg_date>=date_trunc('day',now());+ 
 +====== Hierarchical view of tags  ====== 
 + 
 +Output a list of tags sorted by hierarchy level and names, 
 +with an indentation to represent the hierarchy. 
 + 
 +<code sql> 
 +WITH RECURSIVE tagr(a,_tag_id,name,level) as ( 
 + select 
 +  array[row_number() over (order by name)] as a, 
 +  tag_id, 
 +  name, 
 +  1 as level 
 + from tags where parent_id is null 
 +UNION ALL 
 + select 
 +   tagr.a || row_number() over (order by tags.name), 
 +   tag_id, 
 +   tags.name, 
 +   tagr.level+1 
 + FROM tags JOIN tagr ON tagr._tag_id=tags.parent_id 
 +
 +select repeat('   ', level-1|| name from tagr order by a; 
 </code> </code>
  
  
sql_analysis.1327719358.txt.gz · Last modified: 2012/01/28 02:55 by daniel