PostgreSQL hangout: 3 things to know about the JSON features in PostgreSQL v9.4
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3 Things you should know about JSON Features in PostgreSQL v9.4 27 January 2015
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Transcript of PostgreSQL hangout: 3 things to know about the JSON features in PostgreSQL v9.4
3 Things you should know about JSON Features in
PostgreSQL v9.4
27 January 2015
- JSON was introduced in PostgreSQL v9.2
- Store unstructured data in JSON columns
- Store nested documents and array
- Functions for converting relational data to JSON
- JSON Parsing support introduced in PostgreSQL v9.3
- JSON operator support for parsing the JSON documents
History of JSON in PostgreSQL
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So JSON has been there since PostgreSQL v9.2!
So what’s the fuss all about in v9.4?
• New datatype with storage format – JSONB
• New operators for matching JSON documents
• Index your JSONB fields
What’s new in v9.4
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New Datatype- JSONB
New Storage format
- Is this a new FORMAT? NO!
- It is still JSON that you would have to deal with
- Internally PostgreSQL would use a hstore like ‘binary’ representation to store the JSON Object!
- This makes the parsing more efficient and opens up the door for different access methods (operators) and faster access!
- How? Let’s go over to the next one!
It’s not JSON! It is JSONB!!!
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create table item_catalog
( item_id varchar(50) primary key,
item_description varchar(250),
attributes jsonb );
Example – Catalog of an online store
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Example – Sample Insert
“category “
is an array
“features” is
an array of
sub-
documents
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Example – Another record can be completely different
“features” has different
set of members
New fields which suit the
details of this specific type
of product
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New OperatorsLeverage upon the parsing capability of new format
- So far you could do get various elements of a JSON document
- Get the an array element at specific position- Get a specific member of document- Get JSON object a specific path
- Binary representation of JSONB makes it easier to compare JSON documents
- Check for containment of one JSON object in another- Check for containment of one member in a JSON object- Check of containment of ‘any’ or ‘all’ elements of an array as
members in JSON object
New Operators!
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New JSONB Operators
@>Does the left JSON value contain
within it the right value?
'{"a":1, "b":2}'::jsonb @>
'{"b":2}'::jsonb
<@Is the left JSON value contained within
the right value?
'{"b":2}'::jsonb <@ '{"a":1,
"b":2}'::jsonb
?Does the key/element string exist
within the JSON value?'{"a":1, "b":2}'::jsonb ? 'b'
?|Do any of these
key/element strings exist?
'{"a":1, "b":2, "c":3}'::jsonb
?| array['b', 'c']
?&Do all of these
key/element strings exist?
'["a", "b"]'::jsonb ?&
array['a', 'b']
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Search Product Catalog for SAMSUNG products-
select item_description
from item_catalog
where attributes @>'{"brand":"SAMSUNG"}'::jsonb;
Search Product Catalog for SAMSUNG Mobiles along with their Price-
select item_description, attributes->'price'from item_catalogwhere attributes @> '{"brand":"SAMSUNG"}'::jsonband attributes->'category' ?| array ['Electronics/Mobile and Accessories/Mobiles'];
Example
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Faster Access with IndexesBinary Format stored in Key value pairs is easy to index
- Since JSONB means JSON-Binary, it can be indexed!
- Create GIN indexes to speed up the parsing of JSONB columns
- You have two options to choose from-- The default operator class for operators- @>, ?, ?& and ?|- The non-default operator class (jsonb_path_ops) supports only @>
- Example- CREATE INDEX idxgin_item_catalog ON item_catalog USING gin
(attributes);- CREATE INDEX idxgin_item_catalog_2 ON item_catalog USING gin
(attributes jsonb_path_ops);- CREATE INDEX idxgin_item_catalog_category ON item_catalog USING
gin (( attributes->'category' ));
If PostgreSQL was a Cocktail Party, I would order GIN to go with my JSON!
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- Send in your suggestions!
- If we get enough requests our next hangout will cover a demo on below lines -
- Create a Table with JSONB field
- Populate it using JSON functions from a relational table
- Create GIN index with default operator class
- Use operators to extract and parse JSON data
- Check if index is being used
- Send in suggestions if there is anything specific that you would like to see
Do you want a Live Demo?
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