org.eigenbase.sql.validate
Interface AggregatingScope

All Superinterfaces:

SqlValidatorScope

All Known Implementing Classes:

AggregatingSelectScope

public interface AggregatingScope
extends SqlValidatorScope

An extension to the SqlValidatorScope interface which indicates that the scope is aggregating.

A scope which is aggregating must implement this interface. Such a scope will return the same set of identifiers as its parent scope, but some of those identifiers may not be accessible because they are not in the GROUP BY clause.

Since:

Mar 25, 2003

Version:

$Id: //open/dev/farrago/src/org/eigenbase/sql/validate/AggregatingScope.java#9 $

Author:

jhyde

Method Summary

boolean

checkAggregateExpr(SqlNode expr, boolean deep) Checks whether an expression is constant within the GROUP BY clause.

Methods inherited from interface org.eigenbase.sql.validate.SqlValidatorScope

addChild, findAliases, findAllColumnNames, findQualifyingTableName, fullyQualify, getMonotonicity, getNode, getOperandScope, getOrderList, getValidator, lookupWindow, resolve, resolveColumn, validateExpr

Method Detail

checkAggregateExpr

boolean checkAggregateExpr(SqlNode expr,
                           boolean deep)

Checks whether an expression is constant within the GROUP BY clause. If the expression completely matches an expression in the GROUP BY clause, returns true. If the expression is constant within the group, but does not exactly match, returns false. If the expression is not constant, throws an exception. Examples:

• If we are 'f(b, c)' in 'SELECT a + f(b, c) FROM t GROUP BY a', then the whole expression matches a group column. Return true.
• Just an ordinary expression in a GROUP BY query, such as 'f(SUM(a), 1, b)' in 'SELECT f(SUM(a), 1, b) FROM t GROUP BY b'. Returns false.
• Illegal expression, such as 'f(5, a, b)' in 'SELECT f(a, b) FROM t GROUP BY a'. Throws when it enounters the 'b' operand, because it is not in the group clause.