This document discusses using Redis as a JSON document store through the ReJSON module. It provides an overview of ReJSON, including that it stores JSON data decoded and in a binary format, allows for direct access to JSON elements through JSONPath-like syntax, and includes strongly-typed atomic commands for working with JSON values. Examples are given of basic SET and GET operations as well as the performance benefits of ReJSON compared to alternative approaches of storing JSON in Redis.

1. Redis as a JSON document store
Itamar Haber

2. What is JSON (emphasis mine)
ECMA-404 The JSON Data Interchange Standard
JSON (JavaScript Object Notation) is a lightweight
data-interchange format. It is easy for humans to
read and write. It is easy for machines to parse and
generate.
http://json.org/
2

3. Not a session about the JSON specification...
object
{}
{ members }
members
pair
pair , members
pair
string : value
array
[]
[ elements ]
elements
value
value , elements
3
value
string
number
object
array
true
false
null
string
""
" chars "
chars
char
char chars
char
any-Unicode-
Character-except-
"-or--or-control-
character
"
/
b
f
n
r
t
u four-hex-digits
number
int
int frac
int exp
int frac exp
Int
digit
digit1-9 digits
- digit
- digit1-9 digits
frac
. digits
exp
e digits
digits
digit
digit digits
e
e
e+
e-
E
E+
E-
...though it does fit nicely in a single slide

4. There are three kinds of lies: lies, damned
lies, and JSON standards.
tl;dr Parsing JSON is a Minefield

5. Fact #1: everyone uses JSON

6. Fact #2: many also use Redis

7. 7
JSON Redis
Us
?

8. Two ways for storing JSON in Redis
Serialized, as a raw String
● Just SET/GET it, client
encodes/decodes
● Great for "forklift" ops
● And with Lua scripting:
○ Sub-element access
○ Atomic updates
8
Deserialized, in a Hash
● Decode->HMSET,
HMGET->Encode
● O(1) access
● Follows the Redis
spirit...

9. ReJSON = Redis + JSON

10. ReJSON is
● A custom JSON data type for Redis (v4 Modules API)
● Keys can contain any valid JSON value
○ Scalars, objects or arrays
○ Nested or not
● Data is stored decoded, in binary format
● JSONPath-like syntax for direct access to elements
● Strongly-typed atomic commands

11. 127.0.0.1:6379> JSON.SET scalar . '"Hello JSON!"'
OK
127.0.0.1:6379> JSON.SET object . '{"foo": "bar",
"ans": 42}'
OK
127.0.0.1:6379> JSON.GET object
"{"foo":"bar","ans":42}"
127.0.0.1:6379> JSON.GET object .ans
"42"
ReJSON - basic SET and GET

12. JSON value -> ReJSON tree data structure
redis> JSON.SET j .
'{
"foo": "bar",
"ans": 42
}'
Type: object
foo
ans
Type: string
"bar"
Type: number
42
root
streaming lexer

13. Performance: 3468 bytes, 3 nesting levels
Throughput Average latency
ReJSON Raw JSON & Lua MessagePack & Lua

14. General JSON.DEL, JSON.GET, JSON.MGET, JSON.SET &
JSON.TYPE
Numbers JSON.NUMINCRBY & JSON.NUMMULTBY
Strings JSON.STRAPPEND & JSON.STRLEN
Objects JSON.OBJKEYS & JSON.OBJLEN
Arrays JSON.ARRAPPEND, JSON.ARRINDEX,
JSON.ARRINSERT, JSON.ARRLEN, JSON.ARRPOP &
JSON.ARRTRIM
Other JSON.RESP
ReJSON commands

15. http://rejson.io - Thank you!
Itamar Haber
Chief OSS Education Officer
Redis Labs
@itamarhaber