gengliangwang commented on code in PR #50761:
URL: https://github.com/apache/spark/pull/50761#discussion_r2070941624
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/constraints.scala:
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@@ -259,3 +263,94 @@ case class ForeignKeyConstraint(
copy(userProvidedCharacteristic = c)
}
}
+
+/**
+ * An expression that validates a specific invariant on a column, before
writing into table.
+ *
+ * @param child The fully resolved expression to be evaluated to check the
constraint.
+ * @param columnExtractors Extractors for each referenced column. Used to
generate readable errors.
+ * @param constraintName The name of the constraint.
+ * @param predicateSql The SQL representation of the constraint.
+ */
+case class CheckInvariant(
+ child: Expression,
+ columnExtractors: Seq[(String, Expression)],
+ constraintName: String,
+ predicateSql: String)
+ extends Expression with NonSQLExpression {
+
+ override def children: Seq[Expression] = child +: columnExtractors.map(_._2)
+ override def dataType: DataType = NullType
+ override def foldable: Boolean = false
+ override def nullable: Boolean = true
+
+ override def eval(input: InternalRow): Any = {
+ val result = child.eval(input)
+ if (result == false) {
+ val values = columnExtractors.map {
+ case (column, extractor) => column -> extractor.eval(input)
+ }.toMap
+ throw QueryExecutionErrors.checkViolation(constraintName, predicateSql,
values)
+ }
+ null
+ }
+
+ /**
+ * Generate the code to extract values for the columns referenced in a
violated CHECK constraint.
+ * We build parallel lists of full column names and their extracted values
in the row which
+ * violates the constraint, to be passed to the
[[InvariantViolationException]] constructor
+ * in [[generateExpressionValidationCode()]].
+ *
+ * Note that this code is a bit expensive, so it shouldn't be run until we
already
+ * know the constraint has been violated.
+ */
+ private def generateColumnValuesCode(
Review Comment:
Yes, check ConstraintExpressionSuite
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