Date: Thu, 8 May 2014 23:34:05 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: "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: <20140509033405.GA23254@momjian.us>
References: <20140422223230.GL10046@momjian.us>
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On Thu, May  8, 2014 at 06:39:11PM -0400, Tom Lane wrote:
> I wrote:
> > 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.
> 
> Attached is a draft patch for this.  In addition to the hash logic per se,
> I made these changes:
> 
> * Replaced the K/V prefix bytes with a code that distinguishes the types
> of JSON values.  While this is not of any huge significance for the
> current index search operators, it's basically free to store the info,
> so I think we should do it for possible future use.
> 
> * Fixed the problem with "exists" returning rows it shouldn't.  I
> concluded that the best fix is just to force recheck for exists, which
> allows considerable simplification in the consistent functions.
> 
> * Tried to improve the comments in jsonb_gin.c.
> 
> Barring objections I'll commit this tomorrow, and also try to improve the
> user-facing documentation about the jsonb opclasses.

Looks good.  I was thinking the jsonb_ops name could remain unchanged
and the jsonb_hash_ops could be called jsonb_combo_ops as it combines
the key and value into a single index entry.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +


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