uros-b commented on code in PR #58024:
URL: https://github.com/apache/spark/pull/58024#discussion_r3903434129
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala:
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@@ -1631,3 +1631,66 @@ case class JsonTypeof(child: Expression)
override protected def withNewChildInternal(newChild: Expression):
JsonTypeof =
copy(child = newChild)
}
+
+// Shape qualifier for IS [NOT] JSON: which top-level JSON type to require.
+sealed trait IsJsonShape
+object IsJsonShape {
+ // Per ANSI SQL:2016 T801, IS JSON VALUE is semantically equivalent to bare
IS JSON:
+ // both accept any well-formed JSON value (object, array, or scalar). They
are kept as
+ // separate shapes so the sql() output round-trips faithfully.
+ case object Any extends IsJsonShape // IS JSON (no qualifier)
+ case object Value extends IsJsonShape // IS JSON VALUE
+ case object Scalar extends IsJsonShape // IS JSON SCALAR -- primitives only
(not object/array)
+ case object Array extends IsJsonShape // IS JSON ARRAY
+ case object Object extends IsJsonShape // IS JSON OBJECT
+}
+
+case class IsJson(child: Expression, shape: IsJsonShape = IsJsonShape.Any)
+ extends UnaryExpression
+ with RuntimeReplaceable
+ with ExpectsInputTypes {
+
+ override def inputTypes: Seq[AbstractDataType] =
+ Seq(StringTypeWithCollation(supportsTrimCollation = true))
+
+ override def dataType: DataType = BooleanType
+ // NULL input propagates as NULL (three-valued logic). Invalid JSON yields
false, not NULL,
+ // because json_typeof returns NULL for both cases and the If(IsNull(child),
...) wrapper
+ // in replacement distinguishes them before the shape check runs.
+ override def nullable: Boolean = true
+
+ override def prettyName: String = "is_json"
+
+ override def sql: String = {
+ val shapeSql = shape match {
+ case IsJsonShape.Any => ""
+ case IsJsonShape.Value => " VALUE"
+ case IsJsonShape.Object => " OBJECT"
+ case IsJsonShape.Array => " ARRAY"
+ case IsJsonShape.Scalar => " SCALAR"
+ }
+ s"(${child.sql} IS JSON$shapeSql)"
+ }
+
+ // json_typeof returns NULL for both null input and invalid JSON. The
If(IsNull) wrapper
+ // propagates NULL input as NULL; for invalid JSON json_typeof also returns
NULL but the
+ // child is not NULL, so shapeCheck evaluates to false via IsNotNull.
+ override def replacement: Expression = {
Review Comment:
replacement evaluates child in IsNull and again in JsonTypeof; qualified
predicates may parse it twice.
Nondeterministic operands can therefore return incorrect results.
```
SELECT IF(rand(0) < 0.5, CAST(NULL AS STRING), '{}') IS JSON
FROM range(10000);
```
Correct results can only be NULL or true; this implementation can produce
false.
Bind/evaluate the operand once, preferably in a dedicated validation helper.
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