snuyanzin commented on code in PR #28688:
URL: https://github.com/apache/flink/pull/28688#discussion_r3605968259
##########
flink-python/pyflink/table/expression.py:
##########
@@ -2257,6 +2257,70 @@ def json_unquote(self) -> 'Expression':
"""
return _unary_op("jsonUnquote")(self)
+ def json_length(self, path = None) -> 'Expression':
+ """
+
+ Returns the number of elements in a JSON document, or the
length of the value at the
+ specified path if one is provided.
+
+ Returns None if the argument is None, the input is not valid
JSON, or the path
+ does not locate a value.
+
+ The length is determined as follows:
+ -Scalar values (number, string, boolean) have length 1.
+ -Arrays have a length equal to the number of their
elements.
+ -Objects have a length equal to the number of their
key-value pairs.
+
+
+ Nested arrays and objects each count as a single element and
their contents are not
+ included in the count.
+
+ Lax and strict mode produce the same output, so mode
selection is disabled in this
+ function. For the path argument, use the form:
+
+ path ::= '$' ( '.' <field> | '[' <index> ']' )*
+ field ::= a key in a JSON object
+ index ::= a zero-based position in a JSON array
+
+
+ When provided with a path that uses a wildcard and resolves
to 2 or more paths,
+ 'json_length' resolves to None.
+
+ Because a None result can mean several different things (the
input is not valid
+ JSON, the path does not match anything, or a wildcard path
matched 2 or more
+ nodes), it is recommended to pair json_length with a helper
function so invalid
+ input is handled explicitly rather than silently returning
None:
+ -Without a path, guard the call with is_json to separate
malformed input from a
+ real result.
+ -With a path, use json_exists to tell "the path is absent"
apart from "the path
+ matched but was ambiguous / matched 2 or more nodes".
+
+ e.g.
+ from pyflink.table.expressions import lit, null_of
+ from pyflink.table.types import DataTypes
+
+ # returns the length only for valid JSON, otherwise None
means "invalid input"
+
lit("[1,2,3]").is_json().then(lit("[1,2,3]").json_length(),
null_of(DataTypes.INT()))
+
+ # path is present even when json_length is None due to a
multi-match wildcard
+ lit("{}").json_exists("$.items[*]")
+ lit("{}").json_length("$.items[*]")
+
+ Examples:
+ -JSON_LENGTH('{1: "hello", 2: "bye bye"}') -> 2
+ -JSON_LENGTH('[1,2,3,4,5]') -> 5
+ -JSON_LENGTH('hello') -> 1
+
+ -JSON_LENGTH('{1: "hello", 2: "bye bye"}', '$.1') -> 1
+ -JSON_LENGTH('{1: [1,2,3], 2: "bye bye"}', '$.1') -> 3
+ -JSON_LENGTH('[1,2,3,4,5]', $.[3]) -> 1
+
+ -JSON_LENGTH('[1,2,3,4,5]', '$.[7]') -> None
+ -JSON_LENGTH('{1: "bad", 2: "syntax here ->"', '$.1') ->
None
Review Comment:
a number of examples are invalid here
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