如何从delphi，参数在postgresql COPY命令中使用单引号插入文件名？

Question

I'm having some fun trying to include a filename in a Postgresql script in delphi, the desired string is

  COPY myschema.mytable FROM 'c:\data\data.csv' CSV HEADER;

I know this SQL query is parsed ok by postgresql as I've tested it in pgadmin, the problem is how to generate it in Delphi. Delphi uses single quotes for strings, so even using the QuotedStr method like

TempSQL := 'COPY myschema.mytable FROM '+QuotedStr(myfilename)+ ' CSV HEADER';
ADOQuery1.SQL.Add (TempSQL);

the string is generated as

COPY myschema.mytable FROM ''c:\data\data.csv'' CSV HEADER;

So I'm trying to use Parameters.ParamByName like

TempSQL := 'COPY myschema.mytable FROM :PFileName CSV HEADER';
ADOQuery1.SQL.Add (TempSQL);
FileNameParam := LQuery.Parameters.ParamByName('PFileName');
FileNameParam.DataType := ftstring;
FileNameParam.Value := 'c:\data\data.csv';
ADOQuery1.Open;

Gives the error: ERROR: syntax error at or near "$1"; Error while executing the query. $1 is usually caused by paramnames being the same as column names, thats not the case here, I tried different paramnames. I think the problem is that maybe Parambyname doesn't work for this type of argument, it's normally used like

    SELECT * FROM myschema.mytable WHERE myfield = :myparameter

ie the colon comes after an = which isn't the case with the copy command. Any suggestions welcome. The delphi code basically scans a directory for (1000s of) suitable files and keeps a log of what is imported, maybe I have to interface with the db in a different way entirely.

Answer 1

This code works perfectly in a quick test app, and displays the properly quoted string in the call to ShowMessage , which means there's something other than what you've shown us here going on in your code.

procedure TForm4.FormCreate(Sender: TObject);
var
  TempStr: string;
  MyFileName: string;
begin
  MyFileName := 'somefile.txt';
  TempStr := 'COPY myschema.mytable FROM ' + QuotedStr(myfilename) + ' CSV HEADER';
  ShowMessage(TempStr);
end

The resulting dialog: