Package org.apache.iotdb.db.mpp.plan.statement.component

Class ResultColumn

java.lang.Object

org.apache.iotdb.db.mpp.plan.statement.StatementNode

org.apache.iotdb.db.mpp.plan.statement.component.ResultColumn

public class ResultColumn
extends StatementNode

This class is used to represent a result column of a query.

Assume that we have time series in db as follows:
[ root.sg.d.a, root.sg.d.b, root.sg.e.a, root.sg.e.b ]

Example 1: select a, a + b, udf(udf(b)) from root.sg.d, root.sg.e;
• Step 1: constructed by sql visitor in logical operator:
  result columns:
  [a, a + b, udf(udf(b))]
• Step 2: concatenated with prefix paths in logical optimizer:
  result columns:
  [root.sg.d.a, root.sg.e.a, root.sg.d.a + root.sg.d.b, root.sg.d.a + root.sg.e.b, root.sg.e.a + root.sg.d.b, root.sg.e.a + root.sg.e.b, udf(udf(root.sg.d.b)), udf(udf(root.sg.e.b))]
• Step 3: remove wildcards in logical optimizer:
  result columns:
  [root.sg.d.a, root.sg.e.a, root.sg.d.a + root.sg.d.b, root.sg.d.a + root.sg.e.b, root.sg.e.a + root.sg.d.b, root.sg.e.a + root.sg.e.b, udf(udf(root.sg.d.b)), udf(udf(root.sg.e.b))]

Example 2: select *, a + *, udf(udf(*)) from root.sg.d;
• Step 1: constructed by sql visitor in logical operator:
  result columns:
  [*, a + * , udf(udf(*))]
• Step 2: concatenated with prefix paths in logical optimizer:
  result columns:
  [root.sg.d.*, root.sg.d.a + root.sg.d.*, udf(udf(root.sg.d.*))]
• Step 3: remove wildcards in logical optimizer:
  result columns:
  [root.sg.d.a, root.sg.d.b, root.sg.d.a + root.sg.d.a, root.sg.d.a + root.sg.d.b, udf(udf(root.sg.d.a)), udf(udf(root.sg.d.b))]

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ResultColumn.ColumnType

Constructor Summary

Constructors

Constructor	Description
ResultColumn(Expression expression, java.lang.String alias, ResultColumn.ColumnType columnType)
ResultColumn(Expression expression, ResultColumn.ColumnType columnType)

Method Summary

Modifier and Type	Method	Description
boolean	equals(java.lang.Object o)
java.lang.String	getAlias()
ResultColumn.ColumnType	getColumnType()
Expression	getExpression()
boolean	hasAlias()
int	hashCode()
java.lang.String	toString()

Methods inherited from class org.apache.iotdb.db.mpp.plan.statement.StatementNode

accept

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ResultColumn

public ResultColumn(Expression expression,
                    java.lang.String alias,
                    ResultColumn.ColumnType columnType)

ResultColumn

public ResultColumn(Expression expression,
                    ResultColumn.ColumnType columnType)

Method Detail

getExpression

public Expression getExpression()

hasAlias

public boolean hasAlias()

getAlias

public java.lang.String getAlias()

getColumnType

public ResultColumn.ColumnType getColumnType()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object