[Enhancement] BuiltinFunctionName does not include all built-in functions

[LantaoJin]

What is the bug?
BuiltinFunctionName should include all built-in functions. But some implemented functions such as JSON_DELETE, JSON_APPEND are not included in this file.

opensearch-spark/ppl-spark-integration/src/main/java/org/opensearch/sql/expression/function/BuiltinFunctionName.java

Lines 224 to 228 in c6d8793

	JSON_KEYS(FunctionName.of("json_keys")),
	JSON_VALID(FunctionName.of("json_valid")),
	// JSON_DELETE(FunctionName.of("json_delete")),
	// JSON_APPEND(FunctionName.of("json_append")),
	// JSON_EXTEND(FunctionName.of("json_extend")),

It because that the following code is handling this missing functions:

opensearch-spark/ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/utils/BuiltinFunctionTransformer.java

Lines 202 to 208 in c6d8793

	static Expression builtinFunction(org.opensearch.sql.ast.expression.Function function, List<Expression> args) {
	if (BuiltinFunctionName.of(function.getFuncName()).isEmpty()) {
	ScalaUDF udf = SerializableUdf.visit(function.getFuncName(), args);
	if(udf == null) {
	throw new UnsupportedOperationException(function.getFuncName() + " is not a builtin function of PPL");
	}
	return udf;

BuiltinFunctionName should include all built-in function of PPL-on-Spark. We need to provide a code refactor.

[ykmr1224]

@LantaoJin Is it more like an enhancement?

[LantaoJin]

It's a code refactor work. @qianheng-aws are you interested in contributing this?

[qianheng-aws]

It's a code refactor work. @qianheng-aws are you interested in contributing this?

Yeah, glad to contribute. Will do that work in this week.