Re: default opclass for jsonb (was Re: Call for GIST/GIN/SP-GIST opclass documentation)

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(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +