Message-ID: <536C550F.50108@archidevsys.co.nz>
Date: Fri, 09 May 2014 16:09:51 +1200
From: Gavin Flower <GavinFlower@archidevsys.co.nz>
Organization: ArchiDevSys
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To: Bruce Momjian <bruce@momjian.us>, 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)
References: <20140422223230.GL10046@momjian.us>
 <16527.1398214220@sss.pgh.pa.us> <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> <1888.1399588751@sss.pgh.pa.us>
 <20140509033405.GA23254@momjian.us>
In-Reply-To: <20140509033405.GA23254@momjian.us>
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On 09/05/14 15:34, Bruce Momjian wrote:
> 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.
>
If you have 'jsonb_combo_ops' - then surely 'jsonb_op' should be called 
'jsonb_xxx_ops', where the 'xxx' distinguishes that from 
'jsonb_combo_ops'?  I guess, if any appropriate wording of 'xxx' was too 
cumbersome, then it would be worse.


Cheers,
Gavin


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