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Re: Serializable Isolation without blocking

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: <robertmhaas(at)gmail(dot)com>
Cc: <nicolas(dot)barbier(at)gmail(dot)com>,<gsstark(at)mit(dot)edu>, <pgsql-hackers(at)postgresql(dot)org>, <laurenz(dot)albe(at)wien(dot)gv(dot)at>
Subject: Re: Serializable Isolation without blocking
Date: 2010-01-01 00:45:37
Message-ID: 4B3CF151020000250002DC1F@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas  wrote:
 
> What predicate locking? If you take ACCESS EXCLUSIVE locks on every
> read, that should serialize all access to every table. Predicate
> locking wouldn't do anything, because the table would be completely
> inaccessible to all competing transactions.
 
Yeah, that's the benefit of starting with the ACCESS EXCLUSIVE locks,
but once I've confirmed that I've found all the places to get the
table level locks, the next step is to turn them into table level
SIREAD locks, and then to implement the SSI.  Locking against
referenced objects is the only practical technique for implementing
predicate locking for production environments that I've seen.
 
The phase where I'm making each referenced table totally inaccessible
to all competing transaction should be pretty short-lived.  It just
gives me an interim milestone to test that piece in isolation before
going on to use it; which is great, but not a place to stop for long.
 
Or have I totally misunderstood your suggestion?
 
-Kevin

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