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https://issues.apache.org/jira/browse/FLINK-3754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15278181#comment-15278181
 ] 

ASF GitHub Bot commented on FLINK-3754:
---------------------------------------

Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1958#discussion_r62682155
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/expressions/fieldExpression.scala
 ---
    @@ -20,27 +20,98 @@ package org.apache.flink.api.table.expressions
     import org.apache.calcite.rex.RexNode
     import org.apache.calcite.tools.RelBuilder
     
    -case class UnresolvedFieldReference(override val name: String) extends 
LeafExpression {
    +import org.apache.flink.api.common.typeinfo.TypeInformation
    +import org.apache.flink.api.table.validate.ExprValidationResult
    +
    +object NamedExpression {
    +  private val curId = new java.util.concurrent.atomic.AtomicInteger()
    +  def newExprId: Int = curId.getAndIncrement()
    +}
    +
    +trait NamedExpression extends Expression {
    +  def name: String
    +  def exprId: Int
    +  def toAttribute: Attribute
    +}
    +
    +abstract class Attribute extends LeafExpression with NamedExpression {
    +  override def toAttribute: Attribute = this
    +
    +  def withName(newName: String): Attribute
    +}
    +
    +case class UnresolvedFieldReference(name: String) extends Attribute {
    +  override def exprId: Int = throw new UnresolvedException(s"calling 
exprId on ${this.getClass}")
    +
       override def toString = "\"" + name
     
    +  override def withName(newName: String): Attribute = 
UnresolvedFieldReference(newName)
    +
    +  override def dataType: TypeInformation[_] =
    +    throw new UnresolvedException(s"calling dataType on ${this.getClass}")
    +
    +  override def validateInput(): ExprValidationResult =
    +    ExprValidationResult.ValidationFailure(s"Unresolved reference $name")
    +}
    +
    +case class ResolvedFieldReference(
    +    name: String,
    +    dataType: TypeInformation[_])(
    +    val exprId: Int = NamedExpression.newExprId) extends Attribute {
    +
    +  override def toString = s"'$name"
    +
       override def toRexNode(implicit relBuilder: RelBuilder): RexNode = {
         relBuilder.field(name)
       }
    -}
     
    -case class ResolvedFieldReference(override val name: String) extends 
LeafExpression {
    -  override def toString = s"'$name"
    +  override def withName(newName: String): Attribute = {
    +    if (newName == name) {
    +      this
    +    } else {
    +      ResolvedFieldReference(newName, dataType)(exprId)
    +    }
    +  }
     }
     
    -case class Naming(child: Expression, override val name: String) extends 
UnaryExpression {
    +case class Alias(child: Expression, name: String)
    +    extends UnaryExpression with NamedExpression {
    +  val exprId: Int = NamedExpression.newExprId
    +
       override def toString = s"$child as '$name"
     
       override def toRexNode(implicit relBuilder: RelBuilder): RexNode = {
         relBuilder.alias(child.toRexNode, name)
       }
     
    -  override def makeCopy(anyRefs: Seq[AnyRef]): this.type = {
    +  override def dataType: TypeInformation[_] = child.dataType
    +
    +  override def makeCopy(anyRefs: Array[AnyRef]): this.type = {
         val child: Expression = anyRefs.head.asInstanceOf[Expression]
         copy(child, name).asInstanceOf[this.type]
       }
    +
    +  override def toAttribute: Attribute = {
    +    if (valid) {
    +      ResolvedFieldReference(name, child.dataType)(exprId)
    +    } else {
    +      UnresolvedFieldReference(name)
    +    }
    +  }
    +}
    +
    +case class UnresolvedAlias(
    +    child: Expression,
    +    aliasName: Option[String] = None) extends UnaryExpression with 
NamedExpression {
    +
    +  override def name: String =
    +    throw new UnresolvedException("Invalid call to name on 
UnresolvedAlias")
    +  override def toAttribute: Attribute =
    --- End diff --
    
    can you add a new lines here?


> Add a validation phase before construct RelNode using TableAPI
> --------------------------------------------------------------
>
>                 Key: FLINK-3754
>                 URL: https://issues.apache.org/jira/browse/FLINK-3754
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API
>    Affects Versions: 1.0.0
>            Reporter: Yijie Shen
>            Assignee: Yijie Shen
>
> Unlike sql string's execution, which have a separate validation phase before 
> RelNode construction, Table API lacks the counterparts and the validation is 
> scattered in many places.
> I suggest to add a single validation phase and detect problems as early as 
> possible.



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