The document discusses PostgreSQL's support for various document data formats, including XML, Hstore, JSON, and JSONB, outlining how to create, read, and update data in each format. It highlights the strengths and limitations of each format: XML supports querying but not updating, Hstore allows key indexing but is less performant, and JSON and JSONB offer rich, nested data with varied performance characteristics. References to official documentation and sample codes are included to aid understanding and practical application.

1. PostgreSQL’s Secret
NoSQL Superpowers
Amanda Gilmore

2. Postgres supports several
document data formats.

3. Formats
XML
hstore
json
jsonb

4. How do you choose?
Do you wrap a foreign database?

5. How do you choose?
Do you have a (fairly) standard object schema with weird objects?

6. How do you choose?
Are you worried about lock contention?

7. XML
http://www.postgresql.org/docs/9.5/static/functions-xml.html

8. Schema
CREATE TABLE xml_samples (
id bigserial PRIMARY KEY,
documents xml,
comments text
)

9. Create
INSERT INTO xml_samples (documents, comments) VALUES (
XMLPARSE( DOCUMENT $$<?xml version="1.0"?>
<catalog>
...
</catalog>$$)
, 'This is an entire XML document')

10. Create
--Alternatively, this inserts one node per row
INSERT INTO xml_samples (documents, comments) VALUES (
$$<book id="bk101">
<author>Gambardella, Matthew</author>
<title>XML Developer's Guide</title>
<genre>Computer</genre>
<price>44.95</price>
<publish_date>2000-10-01</publish_date>
<description>An in-depth look at creating applications
with XML.</description>
</book>$$
, 'one book per row, as an XML node')

11. Read
--Gets all titles in the table
SELECT xpath('//book/title', documents) FROM xml_samples
--Gets all info on a book by title
SELECT * FROM xml_samples WHERE (xpath('//book/title/text()'
, documents))[1]::text = 'Midnight Rain'::text

12. Update
Cannot do this natively.

13. hstore
http://www.postgresql.org/docs/9.5/static/hstore.html

14. Schema
CREATE EXTENSION hstore
CREATE TABLE hstore_samples (
id bigserial PRIMARY KEY,
documents hstore,
comments text
)

15. Create
INSERT INTO hstore_samples (documents, comments)
VALUES ('"active_resource"=>"true"
,"resource_name"=>"swimming-swiftly-1234"
,"resource_size_in_mb"=>"30"
,"resource_created_at"=>"2016-03-14 17:20:47.216862"'
, 'this is a straight up K/V hash')

16. Read
--hstores are strings under the hood and require casting
SELECT * from hstore_samples
WHERE (documents -> 'resource_size_in_mb')::int > 30

17. Read
--You can get all of the values for a certain key:
SELECT (documents -> 'resource_name')::text
FROM hstore_samples
--or convert the entire table to an hstore:
SELECT hstore(t) FROM hstore_samples AS t

18. Read
--Pulling multiple values from the document
SELECT (documents -> 'resource_name')::text
, (documents -> 'active_resource')::text
FROM hstore_samples

19. Update
--Cannot do this in place , hence the || operator
UPDATE hstore_samples
SET documents = documents || '"active_resource"=>"false"'::hstore
WHERE documents @> '"resource_name"=>"swimming-swiftly-1234"'::hstore

20. json & jsonb
http://www.postgresql.org/docs/9.5/static/datatype-json.html

21. Read
--get json object. Array element by index (int) or by key
(str)
->
--get json object *by text*
->>
--containment operator, used to get an object by path
@>
--checks for existence of a key
?
http://www.postgresql.org/docs/9.5/static/functions-json.html

22. Schema
CREATE TABLE json_samples (
id bigserial PRIMARY KEY,
text_json json,
binary_json jsonb,
notes text
)

23. Create
INSERT INTO json_samples (text_json, notes) VALUES (
'{
"minStartTimeNs": "1429828653617000000",
"maxEndTimeNs": "1429839639367000000",
"dataSourceId":
"derived:com.google.heart_rate.bpm:com.google.android.gms:merge_heart_rate_bpm"
}'
, 'This is in the text json field')

24. Read
--Can check top-level keys before querying:
SELECT jsonb_object_keys(binary_json) FROM json_samples
--Well formed JSON path:
['point'][0]['value'][0]['fpVal']
--And you can extract specific values from the document:
SELECT binary_json->'point'->0->'value'->0->'fpVal' FROM json_samples

25. --Can check if a given key is present:
SELECT * FROM json_samples WHERE text_json::jsonb ? 'dataSourceId'
SELECT * FROM json_samples WHERE binary_json ? 'dataSourceId'
--And can check if the value of the key matches something:
SELECT * FROM json_samples
WHERE binary_json ->> 'minStartTimeNs' = '1429828653617000000'
Read

26. Update
--Can update at top level:
UPDATE json_samples
SET binary_json = binary_json || '{"address": {
"streetAddress": "123 Test Street",
"city": "Oakland",
"state": "CA",
"postalCode": "94123"
} }'
WHERE binary_json ->> 'lastName' = 'Gilmore'

27. Update
--or use jsonb_set() to drill down the tree:
SELECT jsonb_set(binary_json::jsonb
, '{address, streetAddress}'
, '"456 Lorem Ipsum St"'::jsonb)
FROM json_samples
WHERE binary_json ->> 'lastName' = 'Gilmore'

28. tl;dr
xml Can query on xpath Can’t update
hstore Can index keys Text, less performant
json Richly nested data Text, less performant
jsonb Nested data, fast reads Higher cost writes

29. xml: http://www.postgresql.org/docs/9.5/static/functions-xml.html
hstore: http://www.postgresql.org/docs/9.5/static/hstore.html
json & jsonb: http://www.postgresql.org/docs/9.5/static/functions-json.html
Source for the xml sample: https://msdn.microsoft.com/en-
us/library/ms762271(v=vs.85).aspx
Sample code for this talk on GitHub:
https://github.com/mandagill/PGConfUS_2016_syntax_samples
Links & References

30. Links & References

31. Questions?

32. Thanks, y’all!
amanda@heroku.com
GitHub: mandagill