org.eigenbase.sql
Class SqlAsOperator

java.lang.Object
  org.eigenbase.sql.SqlOperator
      org.eigenbase.sql.SqlSpecialOperator
          org.eigenbase.sql.SqlAsOperator

public class SqlAsOperator
extends SqlSpecialOperator

The AS operator associates an expression with an alias.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/sql/SqlAsOperator.java#15 $

Author:

John V. Sichi

Field Summary

Fields inherited from class org.eigenbase.sql.SqlOperator

MaxPrec, NL

Constructor Summary

SqlAsOperator()
Creates an AS operator.

Method Summary

<R> void	acceptCall(SqlVisitor<R> visitor, SqlCall call, boolean onlyExpressions, SqlBasicVisitor.ArgHandler<R> argHandler) Accepts a SqlVisitor, directing an SqlBasicVisitor.ArgHandler to visit operand of a call.
RelDataType	deriveType(SqlValidator validator, SqlValidatorScope scope, SqlCall call) Derives the type of a call to this operator.
SqlMonotonicity	getMonotonicity(SqlCall call, SqlValidatorScope scope) Returns whether this operator is monotonic.
void	unparse(SqlWriter writer, SqlNode[] operands, int leftPrec, int rightPrec) Writes a SQL representation of a call to this operator to a writer, including parentheses if the operators on either side are of greater precedence.
void	validateCall(SqlCall call, SqlValidator validator, SqlValidatorScope scope, SqlValidatorScope operandScope) Validates a call to this operator.

Methods inherited from class org.eigenbase.sql.SqlSpecialOperator

getSyntax, reduceExpr

Methods inherited from class org.eigenbase.sql.SqlOperator

acceptCall, adjustType, argumentMustBeScalar, checkOperandCount, checkOperandTypes, createCall, createCall, createCall, createCall, equals, getAllowedSignatures, getAllowedSignatures, getKind, getLeftPrec, 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

Constructor Detail

SqlAsOperator

public SqlAsOperator()

Creates an AS operator.

Method Detail

unparse

public void unparse(SqlWriter writer,
                    SqlNode[] operands,
                    int leftPrec,
                    int rightPrec)

Description copied from class: SqlOperator

Writes a SQL representation of a call to this operator to a writer, including parentheses if the operators on either side are of greater precedence.

The default implementation of this method delegates to SqlSyntax.unparse(org.eigenbase.sql.SqlWriter, org.eigenbase.sql.SqlOperator, org.eigenbase.sql.SqlNode[], int, int).

Overrides:

unparse in class SqlSpecialOperator

validateCall

public void validateCall(SqlCall call,
                         SqlValidator validator,
                         SqlValidatorScope scope,
                         SqlValidatorScope operandScope)

Description copied from class: SqlOperator

Validates a call to this operator.

This method should not perform type-derivation or perform validation related related to types. That is done later, by SqlOperator.deriveType(SqlValidator, SqlValidatorScope, SqlCall). This method should focus on structural validation.

A typical implementation of this method first validates the operands, then performs some operator-specific logic. The default implementation just validates the operands.

This method is the default implementation of SqlCall.validate(org.eigenbase.sql.validate.SqlValidator, org.eigenbase.sql.validate.SqlValidatorScope); but note that some sub-classes of SqlCall never call this method.

Overrides:

validateCall in class SqlOperator

Parameters:

call - the call to this operator

validator - the active validator

scope - validator scope

operandScope - validator scope in which to validate operands to this call; usually equal to scope, but not always because some operators introduce new scopes

See Also:

SqlNode.validateExpr(SqlValidator, SqlValidatorScope), SqlOperator.deriveType(SqlValidator, SqlValidatorScope, SqlCall)

acceptCall

public <R> void acceptCall(SqlVisitor<R> visitor,
                           SqlCall call,
                           boolean onlyExpressions,
                           SqlBasicVisitor.ArgHandler<R> argHandler)

Description copied from class: SqlOperator

Accepts a SqlVisitor, directing an SqlBasicVisitor.ArgHandler to visit operand of a call. The argument handler allows fine control about how the operands are visited, and how the results are combined.

Overrides:

acceptCall in class SqlOperator

Parameters:

visitor - Visitor

call - Call to visit

onlyExpressions - If true, ignores operands which are not expressions. For example, in the call to the AS operator

argHandler - Called for each operand

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 SqlOperator

Parameters:

validator - Validator

scope - Scope of validation

call - Call to this operator

Returns:

Type of call

getMonotonicity

public SqlMonotonicity getMonotonicity(SqlCall call,
                                       SqlValidatorScope scope)

Description copied from class: SqlOperator

Returns whether this operator is monotonic.

Default implementation returns SqlMonotonicity.NotMonotonic.

Overrides:

getMonotonicity in class SqlOperator

Parameters:

call - Call to this operator

scope - Scope in which the call occurs