Introduce JSON_EXTRACT function

[wey-gu]

close: #3513

Note, we don't support the path argument in this phase

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number: #3513

Description:

It takes a string and returns a map:

YIELD JSON_EXTRACT('{"a": 1, "b": 2}') AS map_foo
+-------------+
| map_foo     |
+-------------+
| {a: 1, b: 2}|
+-------------+

highlight ( should be included in docs, too)

• "foo", "1", "true" are all valid JSON String though(RFC8259), they are treated as BAD_DATA here due to this function is trying to return either empty/null or Map() in its return value, thus "foo" will be considered to be dirty value.

  Scenario: Test Cases With Invalid JSON String
    When executing query:
      """
      YIELD JSON_EXTRACT('fuzz') AS result;
      """
    Then the result should be, in any order:
      | result   |
      | BAD_DATA |

limitation

• Only Bool, Double, Int, String value and null are supported
• Only depth-1 nested Map is supported now.

Here nested Map depth is 1, it's parsed perfectly:

> YIELD JSON_EXTRACT('{"a": 1, "b": 0.2, "c": {"d": true}}')
+------------------------------------------------------+
| JSON_EXTRACT("{"a": 1, "b": 0.2, "c": {"d": true}}") |
+------------------------------------------------------+
| {a: 1, b: 0.2, c: {d: true}}                         |
+------------------------------------------------------+

Here nested Map depth is 2, the nested item is left as an empty Map():

> YIELD JSON_EXTRACT('{"a": "foo", "b": 0.2, "c": {"d": {"e": 0.1}}}')
+----------------------------------------------------------------+
| JSON_EXTRACT("{"a": "foo", "b": 0.2, "c": {"d": {"e": 0.1}}}") |
+----------------------------------------------------------------+
| {a: "foo", b: 0.2, c: {}}                                      |
+----------------------------------------------------------------+

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:

Added function: JSON_EXTRACT to enable parsing JSON format string into Map.

[jievince]

LGTM

[jievince]

The ctest failed, please fix it.

[jievince]

Lgtm

[jievince]

Lgtm

[Shylock-Hg]

Plz add test in tck.

[wey-gu]

Plz add test in tck.

OK, will do so.
Done :)

[wey-gu]

@Shylock-Hg @jievince @Sophie-Xie it's now ready and rebased :)
Thanks!

[foesa-yang]

vesoft-inc/nebula-docs-cn#2268