ganeshashree commented on code in PR #57559:
URL: https://github.com/apache/spark/pull/57559#discussion_r3705601488
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/json/JsonExpressionEvalUtils.scala:
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@@ -350,6 +357,462 @@ case class JsonTupleEvaluator(foldableFieldNames:
Array[Option[String]]) {
}
}
+/**
+ * The three-state result of navigating a JSON path for `JSON_TABLE`.
`get_json_object` collapses
+ * "the path is absent" and "the value is JSON null" into a single `null`,
which is wrong for
+ * `JSON_TABLE`: `EXISTS` must treat a present-but-null value as existing, and
a value column must
+ * distinguish SQL `NULL` from the literal string `"null"`. This ADT keeps the
two cases distinct.
+ */
+sealed trait JsonPathResult
+object JsonPathResult {
+ /** The path did not match (the key/index is absent). */
+ case object Missing extends JsonPathResult
+ /** The path matched a JSON `null` literal. */
+ case object NullValue extends JsonPathResult
+ /** The path matched a value; `raw` is its verbatim JSON text (including
quoted strings). */
+ case class Found(raw: UTF8String) extends JsonPathResult
+}
+
+/**
+ * A prefix trie over the (wildcard-free) column paths of a single
`JSON_TABLE` invocation, built
+ * once via [[JsonTableEvaluator.buildPathTrie]] and reused for every row. It
lets
+ * [[JsonTableEvaluator.navigateAll]] resolve all columns in a single
traversal of a row item
+ * instead of re-parsing the item once per column.
+ *
+ * Each node groups the paths that share a common prefix: `named`/`indexed`
hold the object-key and
+ * array-index steps to child nodes, and `terminals` lists the result-slot
indices of the columns
+ * whose path ends exactly at this node.
+ */
+private[expressions] final class JsonTablePathTrie {
+ // Result-slot indices of columns whose path terminates at this node.
+ var terminals: List[Int] = Nil
+ // Object-key children, keyed by field name.
+ val named: mutable.HashMap[String, JsonTablePathTrie] = mutable.HashMap.empty
+ // Array-index children, keyed by index.
+ val indexed: mutable.HashMap[Long, JsonTablePathTrie] = mutable.HashMap.empty
+
+ def hasChildren: Boolean = named.nonEmpty || indexed.nonEmpty
+
+ /** True if no column path was inserted (e.g. an ordinality-only table):
nothing to resolve. */
+ def isEmpty: Boolean = terminals.isEmpty && !hasChildren
+}
+
+/**
+ * The result of positioning a parser at a JSON path for the `JSON_TABLE` row
source (see
+ * `positionAt`). Like [[JsonPathResult]] it distinguishes a missing path from
a JSON `null`, but
+ * `AtValue` leaves the parser on the matched value's first token (rather than
serializing it) so
+ * the row source can be streamed.
+ */
+sealed trait PositionResult
+object PositionResult {
+ /** The path did not match. */
+ case object Missing extends PositionResult
+ /** The path matched a JSON `null` literal. */
+ case object NullValue extends PositionResult
+ /** The path matched a value; the parser is positioned at its first token. */
+ case object AtValue extends PositionResult
+}
+
+/**
+ * Row-source and column extraction for the SQL `JSON_TABLE` function. Given
the JSON input, the
+ * (wildcard-free) container path, and whether the row path ended in `[*]`, it
produces the
+ * per-row JSON documents that the
[[org.apache.spark.sql.catalyst.expressions.JsonTable]]
+ * generator then projects into columns via [[navigate]].
Review Comment:
Fixed. Linked to `[[navigateColumns]]`, the projection entry point used by
JsonTable.
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