gpt4 book ai didi

德尔福 Firedac 甲骨文 : Raises Exception When Locating Primary key (VARCHAR or VARCHAR2)

转载 作者:行者123 更新时间:2023-12-02 03:07:00 26 4
gpt4 key购买 nike

Oracle 示例表

   create table appval (
id varchar2(4) not null primary key,
val1 number(38,0) default 0,
val2 number(5,2) default 0);

insert into appval (id,val1) values ('1101', 1500000);
insert into appval (id,val2) values ('1102', 2.5);

delphi (Rad Studio) 示例

type 
TValHelper = class (TComponent)
private
FDataSet: TFDTable;
protected
procedure PrepareTable;
public
constructor CreateHelper(AOwner: TComponent; var ATable: TFDTable); reintroduce;
function GetVal1(AId: string): Currency;
function GetVal2(AId: string): Double;
end;

constructor CreateHelper(AOwner: TComponent; var ATable: TFDTable);
begin
inherited Create(AOwner);
if not Assigned(ATable) then
Raise Exception.Create('Null Parameter passed.');

FDataSet := ATable;
PrepareTable;
end;

procedure TValHelper.PrepareTable;
begin
if not FDataSet.Active then
begin
FDataSet.Connection := Dm.FDConnection;
FDataSet.TableName := 'appval';
FDataSet.Open;
end;
end;

function TValHelper.GetVal1 (AId: string): Currency;
begin
Result := 0; {default value if false}
if AppVal.Locate('id', AId,
[loCaseInsensitive, loPartialKey]) then {<-- Exception}
Result := AppNumVal.Fields[1].AsCurrency;
end;

function TValHelper.GetVal2 (AId: string): Double;
begin
Result := 0; {default value if false}
if AppVal.Locate('id', AId,
[loCaseInsensitive, loPartialKey]) then {<-- Exception}
Result := AppNumVal.Fields[2].AsFloat;
end;

当我调用 GetVal1 函数内部“Locate”时,会引发带有消息的异常

Exception class EFDException with message '[FireDAC][Phys][Ora]-345. 
Data too large for variable
[:FD__LC_ID]. Max len = [4], actual len = [5] Hint:
set the TFDParam.Size to a greater value'.

我尝试使用其他数据库(SQLite)重现此测试,没有像 Oracle 那样引发异常。

这是错误或我的代码中缺少某些内容。有人可以解释一下吗?

我做了一项研究并尝试追踪这个错误我进入了 FireDac.Comp.Client.pas 的可疑区域(德尔福东京10.2)

{LINE 12690}
procedure TFDTable.FetchWindow
begin
{some code}
{line 12769 i Set Watch at Command.CommandText.Text}
Command.CommandText.Add(GenerateSQL);
{Watch value :
'SELECT A.*, A.ROWID AS FD__ROWID'
'FROM APPVAL A'
'WHERE ({FN UCASE(A.ID)} LIKE {FN UCASE(:FD__LC_ID)})'
'ORDER BY A.ID ASC'
'{LIMIT(1)}'
:F__LC_ID <-- is param with size 4

until this
everything goes fine.
}

// check locate params {LINE 12785}
else if IsPrefixed(oParam.Name, C_FD_CmdGenLocate, sField) then begin
oParam.AssignFieldValue(FieldByName(sField), GetLocateRow.ValueS[sField]);
// made LIKE compatible String
if FTableParams.FLocatePartial and
(oParam.DataType in [ftString, ftWideString, ftFixedChar, ftFixedWideChar]) then
oParam.Value := VarToStr(oParam.Value) + '%'; {LINE 12791}
{
something wrong with this oParam.Value Plus 1 char '%'
and i assume field has only 4 so if we increase the field size
manualy value will be padded with space before '%' so this will
still produce exception (oParam.Value always greater +1).
}
end

end;

我该如何解决这个问题。

最佳答案

我们可以称其为错误。 FireDAC 可以在附加 % 字符时增加参数的限制大小。但是,在您的情况下,您似乎希望通过确切的术语而不是部分来查找记录。如果是这样,只需排除 loPartialKey来自您的旗帜 Locate方法调用。如果没有,您可以自己将搜索词修剪一个字符,作为一种快速的肮脏解决方法。

关于德尔福 Firedac 甲骨文 : Raises Exception When Locating Primary key (VARCHAR or VARCHAR2),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45840965/

26 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com