Message-ID: <4FC01232.1090901@agliodbs.com>
Date: Fri, 25 May 2012 16:13:54 -0700
From: Josh Berkus <josh@agliodbs.com>
Organization: PostgreSQL Experts Inc.
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To: pgsql-performance@postgresql.org
Subject: Re: Parallel (concurrent) inserts?
References: <jpovmi$4hp$1@dough.gmane.org>
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> I'm wondering if there is ia document describing which guarantees (if
> any) PostgreSQL makes about concurrency for various operations? Speaking
> in general (i.e. IO can handle it, number of CPU cores and client
> threads is optimal), are fully concurrent operations (independant and
> non-blocking) possible for:

Yes, there's quite a bit of documentation.  Start here:
http://www.postgresql.org/docs/9.1/static/mvcc.html

> 1) An unindexed table?

Yes.

> 2) A table with 1+ ordinary (default btree) indexes? (are there
> constraints on the structure and number of indexes?)

Yes.

> 3) A table with 1+ unique indexes?

Yes.  Note that locking on the unique index may degrade concurrent
throughput of the input stream though, since we have to make sure you're
not inserting two different rows with the same unique indexed value
simulatenously.  It's work as you expect, though.

> 4) A table with other objects on it (foreign keys, check constraints, etc.)?

Yes.  Also concurrent autonumber (sequence) allocations work fine.

In fact, PostgreSQL has no non-concurrent mode, unless you count temp
tables.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com