expression: add builtin json_array_append

[erjiaqing]

What problem does this PR solve?

a part of #7546

What is changed and how it works?

• Get the JSON object from first argument.
• Iterate on every (path, obj) pair
  o. if path is null, do nothing and return null without checking other errors
  o. if path is illegal (invalid or contains wildcard), throw error
  o. if json object at path is not an array, warp it with a array.
  o. append the obj to that array with json.MergeBinary
  o. call Modify to commit change

Original MySQL document:

Appends values to the end of the indicated arrays within a JSON document and returns the result. Returns NULL if any argument is NULL. An error occurs if the json_doc argument is not a valid JSON document or any path argument is not a valid path expression or contains a * or ** wildcard.

The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.

If a path selects a scalar or object value, that value is autowrapped within an array and the new value is added to that array. Pairs for which the path does not identify any value in the JSON document are ignored.

Observed behavior on MySQL 8.0:

MySQL [(none)]> SELECT JSON_ARRAY_APPEND("[]", null, 1, "aaaa", "aaaa");show warnings;
+--------------------------------------------------+
| JSON_ARRAY_APPEND("[]", null, 1, "aaaa", "aaaa") |
+--------------------------------------------------+
| NULL                                             |
+--------------------------------------------------+
1 row in set (0.001 sec)

Empty set (0.000 sec)
MySQL [(none)]> SELECT JSON_ARRAY_APPEND(null, null, 1, "aaaa", "aaaa");show warnings;
+--------------------------------------------------+
| JSON_ARRAY_APPEND(null, null, 1, "aaaa", "aaaa") |
+--------------------------------------------------+
| NULL                                             |
+--------------------------------------------------+
1 row in set (0.001 sec)

Empty set (0.001 sec)

MySQL [(none)]> SELECT JSON_ARRAY_APPEND("", null, 1, "aaaa", "aaaa");show warnings;
ERROR 3141 (22032): Invalid JSON text in argument 1 to function json_array_append: "The document is empty." at position 0.
+-------+------+--------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                |
+-------+------+--------------------------------------------------------------------------------------------------------+
| Error | 3141 | Invalid JSON text in argument 1 to function json_array_append: "The document is empty." at position 0. |
+-------+------+--------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)

MySQL [(none)]> SELECT JSON_ARRAY_APPEND("[", null, 1, "aaaa", "aaaa");show warnings;
ERROR 3141 (22032): Invalid JSON text in argument 1 to function json_array_append: "Invalid value." at position 1.
+-------+------+------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                        |
+-------+------+------------------------------------------------------------------------------------------------+
| Error | 3141 | Invalid JSON text in argument 1 to function json_array_append: "Invalid value." at position 1. |
+-------+------+------------------------------------------------------------------------------------------------+
1 row in set (0.001 sec)

MySQL [(none)]> SELECT JSON_ARRAY_APPEND("null", "$", null);show warnings;
+--------------------------------------+
| JSON_ARRAY_APPEND("null", "$", null) |
+--------------------------------------+
| [null, null]                         |
+--------------------------------------+
1 row in set (0.001 sec)

Empty set (0.001 sec)

MySQL [(none)]> SELECT JSON_ARRAY_APPEND(null, "a", null);show warnings;
+------------------------------------+
| JSON_ARRAY_APPEND(null, "a", null) |
+------------------------------------+
| NULL                               |
+------------------------------------+
1 row in set (0.001 sec)

Empty set (0.001 sec)

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

[morgo]

Thank you for your contribution! It looks like the CI is broken on errcheck.

[codecov-io]

Codecov Report

Merging #9609 into master will increase coverage by 0.0087%.
The diff coverage is 80%.

@@               Coverage Diff               @@
##             master     #9609        +/-   ##
===============================================
+ Coverage   67.3893%   67.398%   +0.0087%     
===============================================
  Files           377       377                
  Lines         79385     79434        +49     
===============================================
+ Hits          53497     53537        +40     
- Misses        21111     21115         +4     
- Partials       4777      4782         +5

[zhouqiang-cl]

/run-all-tests

[morgo]

/run-all-tests

[eurekaka]

/run-all-tests

[lzmhhh123]

/run-all-tests

[eurekaka]

LGTM

[zz-jason]

LGTM