public static HashSet <ColumnExpression> Gather(HashSet <TableAlias> aliases, SelectExpression select)
{
var gatherer = new JoinColumnGatherer(aliases);
gatherer.Gather(select.Where);
return(gatherer.columns);
}
/// <summary>
/// Gets an expression that be used by a query to determines if an outer join had a successful match
/// (as opposed to null columns when no match occurs).
/// </summary>
public virtual Expression GetOuterJoinTest(SelectExpression select)
{
// if the column is used in the join condition (equality test)
// if it is null in the database then the join test won't match (null != null) so the row won't appear
// we can safely use this existing column as our test to determine if the outer join produced a row
// find a column that is used in equality test
var aliases = DeclaredAliasGatherer.Gather(select.From);
var joinColumns = JoinColumnGatherer.Gather(aliases, select).ToList();
if (joinColumns.Count > 0)
{
// prefer one that is already in the projection list.
foreach (var jc in joinColumns)
{
foreach (var col in select.Columns)
{
if (jc.Equals(col.Expression))
{
return(jc);
}
}
}
return(joinColumns[0]);
}
// fall back to introducing a constant
return(Expression.Constant(1, typeof(int?)));
}
public static HashSet <DbColumnExpression> Gather(HashSet <TableAlias> aliases, DbSelectExpression select)
{
var gatherer = new JoinColumnGatherer(aliases);
if (gatherer != null)
{
gatherer.Gather(select.Where);
}
return(gatherer.columns);
}
public virtual Expression GetOuterJoinTest(SelectExpression select)
{
List <ColumnExpression> list = JoinColumnGatherer.Gather(DeclaredAliasGatherer.Gather(select.From), select).ToList <ColumnExpression>();
if (list.Count > 0)
{
foreach (ColumnExpression expression in list)
{
foreach (ColumnDeclaration declaration in select.Columns)
{
if (expression.Equals(declaration.Expression))
{
return(expression);
}
}
}
return(list[0]);
}
return(Expression.Constant(1, typeof(int?)));
}
internal virtual Expression GetOuterJoinTest(DbSelectExpression select)
{
var aliases = DbDeclaredAliasGatherer.Gather(select.From);
var joinColumns = JoinColumnGatherer.Gather(aliases, select).ToList();
if (joinColumns.Count > 0)
{
foreach (var jc in joinColumns)
{
foreach (var col in select.Columns)
{
if (jc.Equals(col.Expression))
{
return(jc);
}
}
}
return(joinColumns[0]);
}
return(Expression.Constant(1, typeof(int?)));
}
Expression GetOuterJoinTest(SelectExpression select)
{
var aliases = TableAliasGatherer.Gather(select.From);
var joinColumns = JoinColumnGatherer.Gather(aliases, select).ToList();
if (joinColumns.Count > 0)
{
// prefer one that is already in the projection list.
foreach (var jc in joinColumns)
{
foreach (var col in select.Columns)
{
if (jc.Equals(col.Expression))
{
return(jc);
}
}
}
return(joinColumns[0]);
}
// fall back to introducing a constant
return(Expression.Constant(1, typeof(int?)));
}
public static HashSet<ColumnExpression> Gather(HashSet<TableAlias> aliases, SelectExpression select)
{
var gatherer = new JoinColumnGatherer(aliases);
gatherer.Gather(select.Where);
return gatherer.columns;
}
