On Mon, Feb 24, 2014 at 9:08 AM, Merlin Moncure <mmonc...@gmail.com> wrote:
> On Mon, Feb 24, 2014 at 8:46 AM, Merlin Moncure <mmonc...@gmail.com> wrote:
>> I still find the phrasing "as jsonb is more efficient for most
>> purposes" to be a bit off  Basically, the text json type is faster for
>> serialization/deserialization pattern (not just document preservation)
>> and jsonb is preferred when storing json and doing repeated
>>subdocument accesses.
> Hm, I'm going to withdraw that.  I had done some testing of simple
> deserialization (cast to text and the like) and noted that jsonb was
> as much as 5x slower.  However, I just did some checking on
> json[b]_populate_recordset though and it's pretty much a wash.

[sorry for noise on this].

Here's the use case coverage as I see it today:

CASE:                json    jsonb     hstore
Static document:     yes      poor      poor
Precise document:    yes      no        no
Serialization:       yes      no        no****
Deserialization:     poor***  yes*      no****
Repeated Access:     poor     yes       yes
Manipulation:        no       no**      yes
GIST/GIN searching:  no       no**      yes

* jsonb gets 'yes' for deserialization assuming andrew's 'two level'
deserialization fix goes in (otherwise 'poor').
** jsonb can't do this today, but presumably will be able to soon
*** 'poor' unless json type also gets the deserialization fix, then 'yes'.
**** hstore can deserialize hstore format, but will rely on json/jsonb
for deserializing json

'Static document' represents edge cases where the json is opaque to
the database but performance -- for example large map polygons.
'Precise document' represents cases where whitespace or key order is important.

Peter asked upthread how to access the various features.  Well, today,
it basically means a bit of nimble casting to different structures
depending on which particular features are important to you, which
IMNSHO is not bad at all as long as we understand that most people who
rely on jsonb will also need hstore for its searching and operators.
Down the line when hstore and jsonb are more flushed out it's going to
come down to an API style choice.


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