Date: Thu, 8 May 2014 16:37:05 +0200
From: Andres Freund <andres@2ndquadrant.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, "David E. Wheeler" <david@justatheory.com>,
 Greg Stark <stark@mit.edu>, Robert Haas <robertmhaas@gmail.com>,
 Heikki Linnakangas <hlinnakangas@vmware.com>,
 Andrew Dunstan <andrew@dunslane.net>, Peter Geoghegan <pg@heroku.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: default opclass for jsonb (was Re: Call for
 GIST/GIN/SP-GIST opclass documentation)
Message-ID: <20140508143705.GA1703@awork2.anarazel.de>
References: <20140422223230.GL10046@momjian.us>
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 <20140506201048.GI30817@momjian.us>
 <16769.1399407530@sss.pgh.pa.us>
 <20140506212020.GK30817@momjian.us>
 <57E8AA44-F816-45F2-BB61-5A854FFB0A97@justatheory.com>
 <28554.1399414853@sss.pgh.pa.us>
 <20140508134701.GO30817@momjian.us> <5819.1399558614@sss.pgh.pa.us>
 <20140508143404.GP30817@momjian.us>
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On 2014-05-08 10:34:04 -0400, Bruce Momjian wrote:
> On Thu, May  8, 2014 at 10:16:54AM -0400, Tom Lane wrote:
> > > Can we hash just the values, not the keys, in jsonb_ops, and hash the
> > > combo in jsonb_hash_ops.  That would give us key-only lookups without a
> > > recheck.
> > 
> > No, because there's nothing in JSON limiting the length of keys, any more
> > than values.
> > 
> > I think the idea of hashing only keys/values that are "too long" is a
> > reasonable compromise.  I've not finished coding it (because I keep
> > getting distracted by other problems in the code :-() but it does not
> > look to be very difficult.  I'm envisioning the cutoff as being something
> > like 128 bytes; in practice that would mean that few if any keys get
> > hashed, I think.
> 
> Yes, that would be nice.  Ideally we would not be doing this so close to
> beta, but it is what it is, and if we need to break binary compatibility
> after beta1, at least we have pg_upgrade.

If we break binary compatibility pg_upgrade won't be able to help. Since
the data files wont be, err, binary compatibile.

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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