Re: Mysterious DB reset

On 03/07/2014 03:10 PM, Israel Brewster wrote:

>>> /usr/local/pgsql/bin/pg_dump -h <domain name of localhost> -U tracking -cs | /usr/local/pgsql/bin/psql -U postgres tracking
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>>> It must have been left over from before I got streaming replication up and working, when this box was still the backup server and not primary -i.e. the domain name in the first half wasn't for the local machine until I swapped machines. Apparently when you do a pg_dump with the -c flag from a server to itself, it does the clean before reading the data, resulting in a new empty database. Thanks again for all the suggestions!
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>> No, -c just tells pg_dump to output clean commands and really only has meaning when you do a plain text dump as above. pg_dump does not clean the data from the running server on its own. What did the cleaning was immediately piping to output of the dump to psql. So basically you created a plain text dump file and fed it back to the server and the dump file included commands to clean out objects. If you had not used -c you would have gotten a bunch of duplicate <something> errors.
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> Right, but I ended up with no data. So what I was getting at was that because I had the -c, which output clean commands, those clean commands were executed before pg_dump dumped the data. You are absolutely correct in saying that it was only executed at all because it was piped to psql, I wasn't claiming otherwise :-) However, the sequence of events clearly is: 1) pg_dump outputs "clean" commands. The pipe to psql runs these, deleting the tables/data/etc. 2) pg_dump outputs the rebuild commands, which are piped to psql, which rebuilds the tables/etc 3) pg_dump tries to dump the data, but there is none (other than the default starting data in the sequences) due to steps 1 and 2 already having been executed (by the pipe to psql) on the same database that pg_dump is running on.
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> Sorry for not being clear :-)

Yea, a snake eating its tail.

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--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com