/// <summary>
/// Is this an equi-join predicate involving columns from the specified tables?
/// On output, if this was indeed an equijoin predicate, "leftVar" is the
/// column of the left table, while "rightVar" is the column of the right table
/// and the predicate itself is of the form "leftVar = rightVar"
/// </summary>
/// <param name="simplePredicateNode">the simple predicate node</param>
/// <param name="leftTableDefinitions">interesting columns of the left table</param>
/// <param name="rightTableDefinitions">interesting columns of the right table</param>
/// <param name="leftVar">join column of the left table</param>
/// <param name="rightVar">join column of the right table</param>
/// <returns>true, if this is an equijoin predicate involving columns from the 2 tables</returns>
private static bool IsEquiJoinPredicate(Node simplePredicateNode,
VarVec leftTableDefinitions, VarVec rightTableDefinitions,
out Var leftVar, out Var rightVar)
{
Var tempLeftVar;
Var tempRightVar;
leftVar = null;
rightVar = null;
if (!Predicate.IsEquiJoinPredicate(simplePredicateNode, out tempLeftVar, out tempRightVar))
{
return(false);
}
if (leftTableDefinitions.IsSet(tempLeftVar) &&
rightTableDefinitions.IsSet(tempRightVar))
{
leftVar = tempLeftVar;
rightVar = tempRightVar;
}
else if (leftTableDefinitions.IsSet(tempRightVar) &&
rightTableDefinitions.IsSet(tempLeftVar))
{
leftVar = tempRightVar;
rightVar = tempLeftVar;
}
else
{
return(false);
}
return(true);
}
internal Predicate GetJoinPredicates(VarVec leftTableDefinitions, VarVec rightTableDefinitions,
out Predicate otherPredicates)
{
Predicate joinPredicate = new Predicate(m_command);
otherPredicates = new Predicate(m_command);
foreach (Node part in m_parts)
{
Var leftTableVar;
Var rightTableVar;
if (Predicate.IsEquiJoinPredicate(part, leftTableDefinitions, rightTableDefinitions, out leftTableVar, out rightTableVar))
{
joinPredicate.AddPart(part);
}
else
{
otherPredicates.AddPart(part);
}
}
return(joinPredicate);
}
