Large array is parsed as an object

[rusuly]

php-mysql-replication/src/MySQLReplication/JsonBinaryDecoder/JsonBinaryDecoderService.php

Line 74 in 064a987

$this->parseObject(BinaryDataReader::UNSIGNED_INT32_LENGTH);

Hi, again.
I think I spotted a bug when looking at the class.
Since mysql-binlog-connector-java hasn't been supported for a while I was looking for how different libraries handle empty holes made by partial updates in JSON(some complain it occurs in MySQL 8.0.16+).

[krowinski]

Hi, good catch its should be array. Funny thing is that in php you can decide when unserialising json is array|object so event if I decode as object still you can do json_encode($json, true) and get array...

Fix and test should be soon tx!

[rusuly]

Also, be informed that in-place updates make empty holes between keys and values as described in the spec

Steps to reproduce (redproduced from MySQL 8.0.16+):

`
UPDATE t1 SET JsonColumn='{"id": 1, "name": "Monica", "types":[1,"123"]}' WHERE Id = 1;
UPDATE t1 SET JsonColumn = JSON_SET(JsonColumn, '$.name', 'Mon') WHERE id = 1;
`

This will create 3-byte hole in the "name" value so you need to advance the stream.

[krowinski]

hmm even is you do

UPDATE t1 SET j='{"id": 1, "name": "Monica", "types":"test"}' WHERE id = 1
UPDATE t1 SET j = JSON_SET(j, '$.name', 'Mon') WHERE id = 1

it will work but you get strange json

"{"id":1,"name":"Mon","types":"catest"}"

its take from Monica - ca and add to types 🙄

raw binary data

string(63) "i�B^���P��10$+idnametypesMonicatest10$+idnametypesMonicatestb�y" hmm

[krowinski]

I don't see any other way to skip unused offset like it was done here

johnyang007/mysql-binlog-connector-java@2fdea43

furthermore I don't see any solution even in mysql-server code

https://github.com/mysql/mysql-server/blob/8.0/sql/json_binary.cc

  the length byte with the new length, and the beginning of the original string
  data. Since the original string "abc" is longer than the new string "XY",
  we'll have a free byte at the end of the string. This byte is left as is
  ('c'). 

Its should work as we read binary data and still it's not cutting correctly.

[rusuly]

Hi,

In my lib I calculate unused space and skip it using Advance method

I think we don't see it in mysql-server code because it is written in C and it accesses memory directly using offsets(it doesn't read the stream in cursor-like style like our libraries do).

[krowinski]

Ok its fixed now, added new test based on yangkun code to verified this and looks good. Also I redone all code based on mysql server code.