Hello,
just coming back from a rescue marathon on this remote server i was telling you.
As i said, the last problem was while doing a 
pg_dump dynacom 
(dynacom is my db'd name)
i kept getting 

pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  compressed data is corrupt
pg_dump: The command was: COPY public.mail_entity (msgno, entno, entparentno....

so i tried dumping the individual mail_entity table, which resulted in the 
following errors:
pg_dump -t mail_entity > /dev/null
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  missing chunk number 2 for toast 
value 133502683
pg_dump: The command was: COPY public.mail_entity (msgno, entno, entparentno, 
entdate, entrecvdate, entsendername, entsenderaddr, entmess
ageid, en;
srv:~>

>From the 76000 rows in that table i found the damaged columns by using the 
>following technique 
(which requires O(log(n)) selects btw lol!!!)
SELECT msgno,entno,entdate from mail_entity where 
coalesce(entdata::text,'')||coalesce(enttext,'') like '%foo%' and msgno/10000 = 
0;
SELECT msgno,entno,entdate from mail_entity where 
coalesce(entdata::text,'')||coalesce(enttext,'') like '%foo%' and msgno/10000 = 
1;
.... until i found the correct subset of 10000 rows
SELECT msgno,entno,entdate from mail_entity where 
coalesce(entdata::text,'')||coalesce(enttext,'') like '%foo%' and msgno/10000 = 
7;
then
SELECT msgno,entno,entdate from mail_entity where 
coalesce(entdata::text,'')||coalesce(enttext,'') like '%foo%' and msgno/1000 = 
70;
SELECT msgno,entno,entdate from mail_entity where 
coalesce(entdata::text,'')||coalesce(enttext,'') like '%foo%' and msgno/1000 = 
71;
...
and so on untill i found the two (it was two of them) bad rows.
i did entdata='' for those two rows, and the selects could be done without 
issues.

however, after that, the pg_dump -t reverted back to the aforementioned error.
Now doing this gives:
srv:~> pg_dump -t mail_entity > /dev/null
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  compressed data is corrupt
pg_dump: The command was: COPY public.mail_entity (msgno, entno, entparentno, 
entdate, entrecvdate, entsendername, entsenderaddr, entmessageid, en;
srv:~>  

Then i did

# CREATE TABLE mail_entity2 AS SELECT * FROM mail_entity;

which went fine

but, for some crazy reason, pg_dump on mail_entity2 also results to an error:
srv:~> pg_dump -t mail_entity2 > /dev/null
pg_dump: SQL command failed
pg_dump: Error message from server: ERROR:  compressed data is corrupt
pg_dump: The command was: COPY public.mail_entity2 (msgno, entno, entparentno, 
entdate, entrecvdate, entsendername, entsenderaddr, entmessageid, e;
srv:~>   

Is there anything i could do to take this very much wanted dump?

-- 
Achilleas Mantzios

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