org.eigenbase.sql.fun
Class SqlCountAggFunction

java.lang.Object
  org.eigenbase.sql.SqlOperator
      org.eigenbase.sql.SqlFunction
          org.eigenbase.sql.SqlAggFunction
              org.eigenbase.sql.fun.SqlCountAggFunction

All Implemented Interfaces:

Aggregation

public class SqlCountAggFunction
extends SqlAggFunction

Definition of the SQL COUNT aggregation function.

COUNT is an aggregator which returns the number of rows which have gone into it. With one argument (or more), it returns the number of rows for which that argument (or all) is not null.

Since:

Oct 17, 2004

Version:

$Id: //open/dev/farrago/src/org/eigenbase/sql/fun/SqlCountAggFunction.java#16 $

Author:

Julian Hyde

Field Summary

static RelDataType

type

Fields inherited from class org.eigenbase.sql.SqlOperator

MaxPrec, NL

Constructor Summary

SqlCountAggFunction()

Method Summary

RelDataType	deriveType(SqlValidator validator, SqlValidatorScope scope, SqlCall call) Derives the type of a call to this operator.
RelDataType[]	getParameterTypes(RelDataTypeFactory typeFactory) Returns the parameter types accepted by this Aggregation.
RelDataType	getReturnType(RelDataTypeFactory typeFactory) Returns the type of the result yielded by this Aggregation.
OJClass[]	getStartParameterTypes()

Methods inherited from class org.eigenbase.sql.SqlAggFunction

isQuantifierAllowed, validateCall

Methods inherited from class org.eigenbase.sql.SqlFunction

getFunctionType, getNameAsId, getParamTypes, getSqlIdentifier, getSyntax, unparse, validateQuantifier

Methods inherited from class org.eigenbase.sql.SqlOperator

acceptCall, acceptCall, adjustType, argumentMustBeScalar, checkOperandCount, checkOperandTypes, createCall, createCall, createCall, createCall, equals, getAllowedSignatures, getAllowedSignatures, getKind, getLeftPrec, getMonotonicity, getName, getOperandCountRange, getOperandTypeChecker, getOperandTypeInference, getReturnTypeInference, getRightPrec, getSignatureTemplate, hashCode, inferReturnType, inferReturnType, isAggregator, isDeterministic, isDynamicFunction, isName, leftPrec, preValidateCall, requiresDecimalExpansion, rewriteCall, rightPrec, toString, unparseListClause, unparseListClause, validateOperands

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eigenbase.rel.Aggregation

getName

Field Detail

type

public static final RelDataType type

Constructor Detail

SqlCountAggFunction

public SqlCountAggFunction()

Method Detail

getParameterTypes

public RelDataType[] getParameterTypes(RelDataTypeFactory typeFactory)

Description copied from interface: Aggregation

Returns the parameter types accepted by this Aggregation.

Parameters:

typeFactory - Type factory to create the types

Returns:

Array of parameter types

getReturnType

public RelDataType getReturnType(RelDataTypeFactory typeFactory)

Description copied from interface: Aggregation

Returns the type of the result yielded by this Aggregation.

Parameters:

typeFactory - Type factory to create the type

Returns:

Result type

getStartParameterTypes

public OJClass[] getStartParameterTypes()

Overrides:

getStartParameterTypes in class SqlAggFunction

deriveType

public RelDataType deriveType(SqlValidator validator,
                              SqlValidatorScope scope,
                              SqlCall call)

Description copied from class: SqlOperator

Derives the type of a call to this operator.

This method is an intrinsic part of the validation process so, unlike SqlOperator.inferReturnType(org.eigenbase.sql.SqlOperatorBinding), specific operators would not typically override this method.

Overrides:

deriveType in class SqlFunction

Parameters:

validator - Validator

scope - Scope of validation

call - Call to this operator

Returns:

Type of call