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| ///////////////////////////////////////////////////////////////////////////
// //
// Copyright (c) 2015 by Charta Software B.V. //
// All rights reserved //
// //
// Version: 1.7.0.83525 //
// Web site: https://pascal.chartasoftware.com/ //
// //
// This code and information are provided "as is" without warranty of //
// any kind. Dissemination of this information or reproduction of //
// this material is strictly forbidden unless prior written permission //
// is obtained from Charta Software B.V.. //
// //
///////////////////////////////////////////////////////////////////////////
unit Sql.Expression;
interface
uses
Boolean,
Condition,
Object_.ReferenceCounted,
Type_;
type
TSqlExpression = class(TReferenceCountedObject)
public
function GetType(): TType; virtual;
function Copy(): TSqlExpression; virtual; abstract;
function IsSimpleOperand(): TBoolean; virtual;
function AggregatesRows(): TBoolean; virtual; // TODO: We should have an Expressions: TSqlExpressionList property so we can provide a solid standard implementation
public
type
TAggregatesRows = class(TCondition<TSqlExpression>)
public
function Matches(const Expression: TSqlExpression): TBoolean; override;
public
class var
Instance: TAggregatesRows;
end;
class constructor Create();
class destructor Destroy();
end;
TSqlSimpleOperandExpression = class(TSqlExpression)
public
function IsSimpleOperand(): TBoolean; override;
end;
TSqlNull = class(TSqlSimpleOperandExpression)
public
function GetType(): TType; override;
function Copy(): TSqlExpression; override;
function CopyNull(): TSqlNull;
end;
TSqlIsNull = class(TSqlExpression)
private
FExpression: TSqlExpression;
procedure SetExpression(const Value: TSqlExpression);
public
constructor Create(Expression: TSqlExpression); reintroduce; virtual;
destructor Destroy(); override;
function GetType(): TType; override;
function Copy(): TSqlExpression; override;
function CopyIsNull(): TSqlIsNull;
function AggregatesRows(): TBoolean; override;
property Expression: TSqlExpression read FExpression write SetExpression;
end;
TSqlAllRows = class(TSqlSimpleOperandExpression)
public
function Copy(): TSqlExpression; override;
function CopyAllRows(): TSqlAllRows;
end;
TSqlAllColumns = class(TSqlSimpleOperandExpression)
public
function Copy(): TSqlExpression; override;
function CopyAllColumns(): TSqlAllColumns;
end;
implementation
uses
Boolean.Type_,
Exception.NotImplemented,
Type_.None;
{ TSqlIsNull }
function TSqlIsNull.AggregatesRows(): TBoolean;
begin
Result := Expression.AggregatesRows();
end;
function TSqlIsNull.Copy(): TSqlExpression;
begin
Result := CopyIsNull();
end;
function TSqlIsNull.CopyIsNull(): TSqlIsNull;
begin
Result := TSqlIsNull.Create(Expression.Copy());
end;
constructor TSqlIsNull.Create(Expression: TSqlExpression);
begin
inherited Create();
Self.Expression := Expression;
end;
destructor TSqlIsNull.Destroy();
begin
Expression.ReleaseReference();
inherited Destroy();
end;
function TSqlIsNull.GetType(): TType;
begin
Result := TBooleanType.Boolean;
end;
procedure TSqlIsNull.SetExpression(const Value: TSqlExpression);
begin
if Value <> Expression then
begin
Value.AddReference();
Expression.ReleaseReference();
FExpression := Value;
end;
end;
{ TSqlExpression }
class constructor TSqlExpression.Create();
begin
TAggregatesRows.Instance := TAggregatesRows.Create();
TAggregatesRows.Instance.AddReference();
end;
class destructor TSqlExpression.Destroy();
begin
TAggregatesRows.Instance.ReleaseReference();
end;
function TSqlExpression.GetType(): TType;
begin
raise ENotImplemented.Create(ClassType, 'GetType');
end;
function TSqlExpression.IsSimpleOperand(): TBoolean;
begin
Result := False;
end;
function TSqlExpression.AggregatesRows(): TBoolean;
begin
Result := False;
end;
{ TSqlNull }
function TSqlNull.Copy(): TSqlExpression;
begin
Result := CopyNull();
end;
function TSqlNull.CopyNull(): TSqlNull;
begin
Result := TSqlNull.Create();
end;
function TSqlNull.GetType(): TType;
begin
Result := TNoneType.Nothing;
end;
{ TSqlAllRows }
function TSqlAllRows.Copy(): TSqlExpression;
begin
Result := CopyAllRows();
end;
function TSqlAllRows.CopyAllRows(): TSqlAllRows;
begin
Result := TSqlAllRows.Create();
end;
{ TSqlAllColumns }
function TSqlAllColumns.Copy(): TSqlExpression;
begin
Result := CopyAllColumns();
end;
function TSqlAllColumns.CopyAllColumns(): TSqlAllColumns;
begin
Result := TSqlAllColumns.Create();
end;
{ TSqlSimpleOperandExpression }
function TSqlSimpleOperandExpression.IsSimpleOperand(): TBoolean;
begin
Result := True;
end;
{ TSqlExpression.TAggregatesRows }
function TSqlExpression.TAggregatesRows.Matches(const Expression: TSqlExpression): TBoolean;
begin
Result := Expression.AggregatesRows();
end;
end.
|