Date: Thu, 8 Nov 2012 01:04:34 -0800 (PST)
From: Denis <socsam@gmail.com>
To: pgsql-performance@postgresql.org
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Subject: Re: [HACKERS] pg_dump and thousands of schemas
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Tom Lane-2 wrote
> Denis &lt;

> socsam@

> &gt; writes:
>> Tom Lane-2 wrote
>>> Hmmm ... so the problem here isn't that you've got 2600 schemas, it's
>>> that you've got 183924 tables.  That's going to take some time no matter
>>> what.
> 
>> I wonder why pg_dump has to have deal with all these 183924 tables, if I
>> specified to dump only one scheme: "pg_dump -n schema_name" or even like
>> this to dump just one table "pg_dump -t 'schema_name.comments' "  ?
> 
> It has to know about all the tables even if it's not going to dump them
> all, for purposes such as dependency analysis.
> 
>> We have a web application where we create a schema with a number of
>> tables
>> in it for each customer. This architecture was chosen to ease the process
>> of
>> backup/restoring data.
> 
> I find that argument fairly dubious, but in any case you should not
> imagine that hundreds of thousands of tables are going to be cost-free.
> 
> 			regards, tom lane
> 
> 
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Still I can't undesrtand why pg_dump has to know about all the tables? For
example I have such an easy table 
CREATE TABLE "CLog" (
    "fromUser" integer,
    "toUser" integer,
    message character varying(2048) NOT NULL,
    "dateSend" timestamp without time zone NOT NULL
);
no foreign keys, it doesn't use partitioning, it doesn't have any relations
to any other table. Why pg_dump has to gother information about ALL the
tables in the database just to dump one this table?


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