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new bc020f4 Add docs for the JSON data type (#184)
bc020f4 is described below
commit bc020f42473cf92f2cd852a88dae8034a47986ed
Author: Twice <[email protected]>
AuthorDate: Wed Jan 3 13:18:08 2024 +0800
Add docs for the JSON data type (#184)
* Add docs for the JSON data type
* fix typo
* fix typo
---
community/data-structure-on-rocksdb.md | 27 +++++++++++++++++++++++++--
1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/community/data-structure-on-rocksdb.md
b/community/data-structure-on-rocksdb.md
index 306172f..7a4e12a 100644
--- a/community/data-structure-on-rocksdb.md
+++ b/community/data-structure-on-rocksdb.md
@@ -42,8 +42,10 @@ The values encoded for other data types in flags can be
found in the table below
| Set | 4 |
| ZSet | 5 |
| Bitmap | 6 |
-| Sortedint | 7 |
+| SortedInt | 7 |
| Stream | 8 |
+| BloomFilter| 9 |
+| JSON | 10 |
In the encoding version `0`, `expire` is stored in seconds and as a 4byte
field (32bit integer), `size` is stored as also a 4byte field (32bit integer);
while in the encoding version `1`, `expire` is stored in milliseconds and as a
8byte field (64bit integer), `size` is stored as also a 8byte field (64bit
integer).
@@ -263,7 +265,7 @@ key|version|EID MS|EID SEQ => | encoded value |
## Bloom Filter
-Redis Bloom filter is a space-efficient probabilistic data structure used to
test whether an element is a member of a set. It's implemented as a Redis
module (https://redis.io/docs/data-types/probabilistic/bloom-filter/), which
means it can be used to efficiently perform set membership tests.
+Redis Bloom filter is a space-efficient probabilistic data structure used to
test whether an element is a member of a set. It's implemented as [a Redis
module](https://redis.io/docs/data-types/probabilistic/bloom-filter/), which
means it can be used to efficiently perform set membership tests.
The underlying structure of a Bloom filter is a bit array, which is a
fixed-size array of bits, typically implemented as a contiguous block of memory
and storage. We choose "split block bloom filter", as described in section 2.1
of [Network Applications of Bloom Filters: A
Survey](https://www.eecs.harvard.edu/~michaelm/postscripts/im2005b.pdf). In a
split block bloom filter, the bit array is divided into fixed-size blocks, and
each block is treated as an independent Bloom filter. This ap [...]
@@ -289,3 +291,24 @@ key|index => | filter |
+---------------+
```
+## JSON
+
+Kvrocks supports the JSON data type just like
[RedisJSON](https://redis.io/docs/data-types/json/), which implements various
data operations on [ECMA-404 The JSON Data Interchange
Standard](https://ecma-international.org/publications-and-standards/standards/ecma-404/).
+
+The current underlying encoding of JSON data type is relatively simple and
similar to String:
+
+```
+ +----------+------------+-----------+--------------------+
+key => | flags | expire | format | payload |
+ | (1byte) | (Ebyte) | (1byte) | (Nbyte) |
+ +----------+------------+-----------+--------------------+
+```
+
+where the `payload` is a string encoded in the corresponding `format`:
+
+| format | enum value |
+|------------|------------|
+| JSON | 0 |
+| CBOR | 1 |
+
+Also, if we decide to add a more IO-friendly format to avoid reading all
payload to the memory before searching an element via JSONPath or seperate a
relatively large JSON to multiple key-values, we can take advantage of the
`format` field.
