public void EliminateJoins(SelectExpression selectExpression)
{
if (selectExpression == null)
{
return;
}
for (var i = selectExpression.Tables.Count - 1; i >= 0; i--)
{
var tableExpression = selectExpression.Tables[i];
if (tableExpression is LeftOuterJoinExpression joinExpressionBase)
{
_tables.Clear();
_columns.Clear();
_canEliminate = true;
Visit(joinExpressionBase.Predicate);
if (_canEliminate &&
_columns.Count > 0 &&
_columns.Count % 2 == 0 &&
_tables.Count == 2 &&
_tables[0].DatabaseName == _tables[1].DatabaseName &&
_tables[0].Table == _tables[1].Table &&
_tables[0].Schema == _tables[1].Schema)
{
for (var j = 0; j < _columns.Count - 1; j += 2)
{
if (_columns[j].Name != _columns[j + 1].Name)
{
_canEliminate = false;
break;
}
}
if (_canEliminate)
{
var newTableExpression
= _tables.Single(t => !ReferenceEquals(t, joinExpressionBase.TableExpression));
selectExpression.RemoveTable(joinExpressionBase);
if (ReferenceEquals(selectExpression.ProjectStarTable, joinExpressionBase))
{
selectExpression.ProjectStarTable
= selectExpression.GetTableForQuerySource(newTableExpression.QuerySource);
}
// selectExpression.UpdateTableReference(joinExpressionBase.TableExpression, newTableExpression);
}
}
}
}
}
