spark Min 源码
spark Min 代码
文件路径：/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Min.scala
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.sql.catalyst.expressions.aggregate
import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
import org.apache.spark.sql.catalyst.dsl.expressions._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.trees.UnaryLike
import org.apache.spark.sql.catalyst.util.TypeUtils
import org.apache.spark.sql.types._
@ExpressionDescription(
usage = "_FUNC_(expr) - Returns the minimum value of `expr`.",
examples = """
Examples:
> SELECT _FUNC_(col) FROM VALUES (10), (-1), (20) AS tab(col);
-1
""",
group = "agg_funcs",
since = "1.0.0")
case class Min(child: Expression) extends DeclarativeAggregate with UnaryLike[Expression] {
override def nullable: Boolean = true
// Return data type.
override def dataType: DataType = child.dataType
override def checkInputDataTypes(): TypeCheckResult =
TypeUtils.checkForOrderingExpr(child.dataType, "function min")
private lazy val min = AttributeReference("min", child.dataType)()
override lazy val aggBufferAttributes: Seq[AttributeReference] = min :: Nil
override lazy val initialValues: Seq[Expression] = Seq(
/* min = */ Literal.create(null, child.dataType)
)
override lazy val updateExpressions: Seq[Expression] = Seq(
/* min = */ least(min, child)
)
override lazy val mergeExpressions: Seq[Expression] = {
Seq(
/* min = */ least(min.left, min.right)
)
}
override lazy val evaluateExpression: AttributeReference = min
override protected def withNewChildInternal(newChild: Expression): Min = copy(child = newChild)
}
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