Ramin Gharib created FLINK-40545:
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Summary: Add parseJson() and tryParseJson() Table API expression
methods
Key: FLINK-40545
URL: https://issues.apache.org/jira/browse/FLINK-40545
Project: Flink
Issue Type: Improvement
Reporter: Ramin Gharib
Assignee: Ramin Gharib
{\{PARSE_JSON}} and \{{TRY_PARSE_JSON}} parse a JSON string into a
\{{VARIANT}}. They are
available in SQL and as \{{BuiltInFunctionDefinitions}}, but unlike almost
every other JSON
function they have no dedicated Table API expression method. Users must fall
back to the
generic \{{call()}}:
{code:java}
call("PARSE_JSON", $("f")) // string name
call(BuiltInFunctionDefinitions.PARSE_JSON, $("f")) // or the definition
{code}
Most JSON functions already expose a fluent method on \{{BaseExpressions}} —
\{{jsonQuote()}},
{\{jsonUnquote()}}, \{{isJson()}}, \{{jsonExists()}}, \{{jsonValue()}},
\{{jsonQuery()}}, etc.
{\{PARSE_JSON}}/\{{TRY_PARSE_JSON}} are the exception, which is inconsistent
and hurts
discoverability.
h3. Proposed change
Add the two methods to \{{BaseExpressions}} following the existing
\{{jsonQuote()}} pattern:
{code:java}
public OutType parseJson() {
return toApiSpecificExpression(unresolvedCall(PARSE_JSON,
objectToExpression(toExpr())));
}
public OutType tryParseJson() {
return toApiSpecificExpression(unresolvedCall(TRY_PARSE_JSON,
objectToExpression(toExpr())));
}
{code}
Usage becomes:
{code:java}
$("f").parseJson() // instead of call("PARSE_JSON", $("f"))
$("f").tryParseJson()
{code}
Also update for parity:
* PyFlink Table API (\{{flink-python/pyflink/table/expression.py}})
* Table API function documentation (JSON functions section)
h3. Context
Surfaced in the FLINK-37926 review (VARIANT-to-constructed casts): the cast
tests use
{\{call("PARSE_JSON", ...)}} because no Table API method exists.
{code}
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