chenhao-db commented on code in PR #45708:
URL: https://github.com/apache/spark/pull/45708#discussion_r1541513308
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/variant/variantExpressions.scala:
##########
@@ -63,3 +70,300 @@ case class ParseJson(child: Expression) extends
UnaryExpression
override protected def withNewChildInternal(newChild: Expression): ParseJson
=
copy(child = newChild)
}
+
+// A path segment in the `VariantGet` expression. It represents either an
object key access (when
+// `key` is not null) or an array index access (when `key` is null).
+case class PathSegment(key: String, index: Int)
+
+object VariantPathParser extends RegexParsers {
+ private def root: Parser[Char] = '$'
+
+ // Parse index segment like `[123]`.
+ private def index: Parser[PathSegment] =
+ for {
+ index <- '[' ~> "\\d+".r <~ ']'
+ } yield {
+ PathSegment(null, index.toInt)
+ }
+
+ // Parse key segment like `.name`, `['name']`, or `["name"]`.
+ private def key: Parser[PathSegment] =
+ for {
+ key <- '.' ~> "[^\\.\\[]+".r | "['" ~> "[^\\'\\?]+".r <~ "']" |
+ "[\"" ~> "[^\\\"\\?]+".r <~ "\"]"
+ } yield {
+ PathSegment(key, 0)
+ }
+
+ private val parser: Parser[List[PathSegment]] = phrase(root ~> rep(key |
index))
+
+ def parse(str: String): Option[Array[PathSegment]] = {
+ this.parseAll(parser, str) match {
+ case Success(result, _) => Some(result.toArray)
+ case _ => None
+ }
+ }
+}
+
+/**
+ * The implementation for `variant_get` and `try_variant_get` expressions.
Extracts a sub-variant
+ * value according to a path and cast it into a concrete data type.
+ * @param child The source variant value to extract from.
+ * @param path A literal path expression. It has the same format as the JSON
path.
+ * @param schema The target data type to cast into.
+ * @param failOnError Controls whether the expression should throw an
exception or return null if
+ * the cast fails.
+ * @param timeZoneId A string identifier of a time zone. It is required by
timestamp-related casts.
+ */
+case class VariantGet(
+ child: Expression,
+ path: Expression,
+ schema: DataType,
+ failOnError: Boolean,
+ timeZoneId: Option[String] = None)
+ extends BinaryExpression
+ with TimeZoneAwareExpression
+ with NullIntolerant
+ with ExpectsInputTypes
+ with CodegenFallback
+ with QueryErrorsBase {
+ override def checkInputDataTypes(): TypeCheckResult = {
+ val check = super.checkInputDataTypes()
+ if (check.isFailure) {
+ check
+ } else if (!path.foldable) {
+ DataTypeMismatch(
+ errorSubClass = "NON_FOLDABLE_INPUT",
+ messageParameters = Map(
+ "inputName" -> toSQLId("path"),
+ "inputType" -> toSQLType(path.dataType),
+ "inputExpr" -> toSQLExpr(path)
+ )
+ )
+ } else if (!VariantGet.checkDataType(schema)) {
+ DataTypeMismatch(
+ errorSubClass = "CAST_WITHOUT_SUGGESTION",
+ messageParameters = Map(
+ "srcType" -> toSQLType(VariantType),
+ "targetType" -> toSQLType(schema)
+ )
+ )
+ } else {
+ TypeCheckResult.TypeCheckSuccess
+ }
+ }
+
+ override lazy val dataType: DataType = schema.asNullable
+
+ @transient private lazy val parsedPath = {
+ val pathValue = path.eval().toString
+ VariantPathParser.parse(pathValue).getOrElse {
+ throw QueryExecutionErrors.invalidVariantGetPath(pathValue, prettyName)
+ }
+ }
+
+ final override def nodePatternsInternal(): Seq[TreePattern] =
Seq(VARIANT_GET)
+
+ override def inputTypes: Seq[AbstractDataType] = Seq(VariantType, StringType)
+
+ override def prettyName: String = if (failOnError) "variant_get" else
"try_variant_get"
+
+ override def nullable: Boolean = true
+
+ protected override def nullSafeEval(input: Any, path: Any): Any = {
Review Comment:
I didn't mean writing everything by hand. Essentially, we create a method
that implements `VariantGet`, and the class only needs some boilerplate code to
call this method (similar to the code in `StaticInvoke` itself).
There is still another reason why I don't like `StaticInvoke`. In the
future, I will write some optimizer rules on `VariantGet` (e.g., to push it
down a join). This is why I added a new `TreePattern` `VARIANT_GET` in this PR.
The optimizer rule will run after `RuntimeReplaceable` expression is replaced,
so it will become `StaticInvoke` and no longer has this tree pattern, and the
optimizer rule can no longer prune expressions. Plus, matching against
`StaticInvoke` is also more complex than matching against `VariantGet`.
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