org.apache.iotdb.db.query.expression

类 ResultColumn

java.lang.Object

org.apache.iotdb.db.query.expression.ResultColumn

public class ResultColumn
extends Object

ResultColumn 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))]

构造器概要

构造器

构造器和说明
ResultColumn(Expression expression)
ResultColumn(Expression expression, String alias)

方法概要

限定符和类型	方法和说明
List<PartialPath>	collectPaths()
void	concat(List<PartialPath> prefixPaths, List<ResultColumn> resultColumns, boolean needAliasCheck)
boolean	equals(Object o)
String	getAlias()
TSDataType	getDataType()
Expression	getExpression()
String	getExpressionString()
String	getResultColumnName()
boolean	hasAlias()
int	hashCode()
void	removeWildcards(WildcardsRemover wildcardsRemover, List<ResultColumn> resultColumns, boolean needAliasCheck)
void	setDataType(TSDataType dataType)
String	toString()

从类继承的方法 java.lang.Object

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

构造器详细资料

ResultColumn

public ResultColumn(Expression expression,
                    String alias)

ResultColumn

public ResultColumn(Expression expression)

方法详细资料

concat

public void concat(List<PartialPath> prefixPaths,
                   List<ResultColumn> resultColumns,
                   boolean needAliasCheck)
            throws LogicalOptimizeException

参数:

prefixPaths - prefix paths in the from clause

resultColumns - used to collect the result columns

needAliasCheck - used to skip illegal alias judgement here. Including !isGroupByLevel because count(*) may be * unfolded to more than one expression, but it still can be aggregated together later.

抛出:

LogicalOptimizeException

removeWildcards

public void removeWildcards(WildcardsRemover wildcardsRemover,
                            List<ResultColumn> resultColumns,
                            boolean needAliasCheck)
                     throws LogicalOptimizeException

参数:

wildcardsRemover - used to remove wildcards from expression and apply slimit & soffset control

resultColumns - used to collect the result columns

needAliasCheck - used to skip illegal alias judgement here. Including !isGroupByLevel because count(*) may be * unfolded to more than one expression, but it still can be aggregated together later.

抛出:

LogicalOptimizeException

collectPaths

public List<PartialPath> collectPaths()

getExpression

public Expression getExpression()

hasAlias

public boolean hasAlias()

getAlias

public String getAlias()

getResultColumnName

public String getResultColumnName()

getExpressionString

public String getExpressionString()

setDataType

public void setDataType(TSDataType dataType)

getDataType

public TSDataType getDataType()

toString

public String toString()

覆盖:

toString 在类中 Object

hashCode

public final int hashCode()

覆盖:

hashCode 在类中 Object

equals

public final boolean equals(Object o)

覆盖:

equals 在类中 Object