Airblader commented on a change in pull request #16776:
URL: https://github.com/apache/flink/pull/16776#discussion_r687674609
##########
File path: docs/data/sql_functions.yml
##########
@@ -596,6 +596,41 @@ json:
'strict $.b' FALSE ON ERROR);
```
+ - sql: JSON_VALUE(jsonValue, path [RETURNING <expr>] [ { NULL | ERROR |
DEFAULT <defaultExpr> } ON EMPTY ] [ { NULL | ERROR | DEFAULT <defaultExpr> }
ON ERROR ])
+ table: STRING.jsonValue(STRING path [, returnType, onEmpty,
defaultOnEmpty, onError, defaultOnError])
+ description: |
+ Extracts a scalar from a JSON string.
+
+ This method searches a JSON string for a given path expression and
returns the value if the
+ value at that path is scalar. Non-scalar values cannot be returned. By
default, the value is
+ returned as `DataTypes#STRING()`. Using `returningType` a different type
can be chosen, with
+ types with the following type roots being supported:
+
+ * `VARCHAR`
+ * `BOOLEAN`
+ * `INTEGER`
+ * `DOUBLE`
+
+ For empty path expressions or errors a behavior can be defined to either
return `null`, raise
+ an error or return a defined default value instead. When omitted, the
default is
+ `NULL ON EMPTY` or `NULL ON ERROR`, respectively.
+
+ ```
+ // STRING: "true"
+ JSON_VALUE('{"a": true}', '$.a')
+
+ // BOOLEAN: true
+ JSON_VALUE('{"a": true}', '$.a' RETURNING BOOLEAN)
+
+ // BOOLEAN: 'false'
Review comment:
> Is this still boolean? Derived from the default value or how does this
work?
Oops, no; it will be a string. The default value is applied before the
conversion to the output type.
> Does the default/error value need to be the same type as return type?
It does not, which was part of the point of this example (and will hopefully
be clear after I fix it)
> Does the default/error value need to be a literal?
It doesn't, and of course that also means the default value can cause an
error as well, which has defined behavior. I'll add a sentence about that.
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