Refactor exclusion of virtual columns in various places:

* introduce TDBQuery.ColIsVirtal() returning a boolean for a column index, and use that instead of examining a columns virtuality everywhere
* exclude virtual column when exporting SQL code in the grid export dialog - see #53
* sql export dialog must not activate edit mode on a result, as this introduces endless loops
* instead, move some code out of PrepareEditing into PrepareColumnAttributes, which we can now call separately without activating edit mode

source/dbconnection.pas

@@ -595,6 +595,7 @@ type
       function ColIsPrimaryKeyPart(Column: Integer): Boolean; virtual; abstract;
       function ColIsUniqueKeyPart(Column: Integer): Boolean; virtual; abstract;
       function ColIsKeyPart(Column: Integer): Boolean; virtual; abstract;
+      function ColIsVirtual(Column: Integer): Boolean;
       function ColAttributes(Column: Integer): TTableColumn;
       function IsNull(Column: Integer): Boolean; overload; virtual; abstract;
       function IsNull(Column: String): Boolean; overload;
@@ -615,6 +616,7 @@ type
       function TableName: String; virtual; abstract;
       function QuotedDbAndTableName: String;
       procedure DiscardModifications;
+      procedure PrepareColumnAttributes;
       procedure PrepareEditing;
       property RecNo: Int64 read FRecNo write SetRecNo;
       property Eof: Boolean read FEof;
@@ -6109,7 +6111,7 @@ begin
   Result := nil;
   if (Column < 0) or (Column >= FColumnOrgNames.Count) then
     raise EDatabaseError.CreateFmt(_('Column #%s not available.'), [IntToStr(Column)]);
-  if FEditingPrepared then begin
+  if FColumns <> nil then begin
     for i:=0 to FColumns.Count-1 do begin
       if FColumns[i].Name = FColumnOrgNames[Column] then begin
         Result := FColumns[i];
@@ -6181,6 +6183,18 @@ begin
 end;
 
 
+function TDBQuery.ColIsVirtual(Column: Integer): Boolean;
+var
+  Col: TTableColumn;
+begin
+  Result := False;
+  Col := ColAttributes(Column);
+  if Col <> nil then begin
+    Result := not Col.Virtuality.IsEmpty;
+  end;
+end;
+
+
 function TMySQLQuery.IsNull(Column: Integer): Boolean;
 begin
   if FEditingPrepared and Assigned(FCurrentUpdateRow) then
@@ -6256,17 +6270,14 @@ begin
 end;
 
 
-procedure TDBQuery.PrepareEditing;
+procedure TDBQuery.PrepareColumnAttributes;
 var
   CreateCode, Dummy, DB: String;
   DBObjects: TDBObjectList;
   LObj, Obj: TDBObject;
 begin
   // Try to fetch column names and keys
-  if FEditingPrepared then
-    Exit;
   // This is probably a VIEW, so column names need to be fetched differently
-
   Obj := nil;
   if FDBObject <> nil then
     Obj := FDBObject
@@ -6294,6 +6305,15 @@ begin
     lntView:
       Connection.ParseViewStructure(CreateCode, Obj, FColumns, Dummy, Dummy, Dummy, Dummy, Dummy);
   end;
+end;
+
+
+procedure TDBQuery.PrepareEditing;
+begin
+  // Try to fetch column names and keys and init update data
+  if FEditingPrepared then
+    Exit;
+  PrepareColumnAttributes;
   FreeAndNil(FUpdateData);
   FUpdateData := TUpdateData.Create(True);
   FEditingPrepared := True;

source/exportgrid.pas

@@ -759,7 +759,7 @@ begin
             tmp := tmp + ' (';
             Col := Grid.Header.Columns.GetFirstVisibleColumn;
             while Col > NoColumn do begin
-              if Col <> ExcludeCol then
+              if (Col <> ExcludeCol) and (not GridData.ColIsVirtual(Col)) then
                 tmp := tmp + GridData.Connection.QuoteIdent(Grid.Header.Columns[Col].Text)+', ';
               Col := Grid.Header.Columns.GetNextVisibleColumn(Col);
             end;
@@ -829,7 +829,9 @@ begin
             end;
 
             efSQLInsert, efSQLReplace, efSQLDeleteInsert: begin
-              if GridData.IsNull(Col) then
+              if GridData.ColIsVirtual(Col) then
+                Data := ''
+              else if GridData.IsNull(Col) then
                 Data := 'NULL'
               else if (GridData.DataType(Col).Index = dtBit) and GridData.Connection.Parameters.IsMySQL then
                 Data := 'b' + esc(Data)
@@ -839,6 +841,7 @@ begin
                 Data := esc(Data)
               else if Data = '' then
                 Data := esc(Data);
+              if not Data.IsEmpty then
                 tmp := tmp + Data + ', ';
             end;
 

source/main.pas

@@ -4533,7 +4533,6 @@ var
   i: Integer;
   Value: String;
   IsNull, AllowNewNode: Boolean;
-  TableCol: TTableColumn;
 begin
   Grid := ActiveGrid;
   Results := GridResult(Grid);
@@ -4559,8 +4558,7 @@ begin
           continue; // Ignore invisible key column
         if Results.ColIsPrimaryKeyPart(i) then
           continue; // Empty value for primary key column
-        TableCol := Results.ColAttributes(i);
+        if Results.ColIsVirtual(i) then
-        if (TableCol <> nil) and (not TableCol.Virtuality.IsEmpty) then
           continue; // Don't copy virtual column value
         Results.RecNo := DupeNum^;
         Value := Results.Col(i);

source/tabletools.pas

@@ -1602,9 +1602,6 @@ begin
       TargetDbAndObject := Quoter.QuoteIdent(DBObj.Name);
       if ToDb then
         TargetDbAndObject := Quoter.QuoteIdent(FinalDbName) + '.' + TargetDbAndObject;
-      // Parse columns, so we can check for special things like virtual columns
-      ColumnList := TTableColumnList.Create(True);
-      DBObj.Connection.ParseTableStructure(DBObj.CreateCode, ColumnList, nil, nil);
       Offset := 0;
       RowCount := 0;
       // Calculate limit so we select ~100MB per loop
@@ -1623,6 +1620,7 @@ begin
         Inc(Offset, Limit);
         if Data.RecordCount = 0 then
           break;
+        Data.PrepareColumnAttributes;
         BaseInsert := 'INSERT INTO ';
         if comboExportData.Text = DATA_INSERTNEW then
           BaseInsert := 'INSERT IGNORE INTO '
@@ -1630,7 +1628,7 @@ begin
           BaseInsert := 'REPLACE INTO ';
         BaseInsert := BaseInsert + TargetDbAndObject + ' (';
         for i:=0 to Data.ColumnCount-1 do begin
-          if ColumnList[i].Virtuality.IsEmpty then
+          if not Data.ColIsVirtual(i) then
             BaseInsert := BaseInsert + Quoter.QuoteIdent(Data.ColumnNames[i]) + ', ';
         end;
         Delete(BaseInsert, Length(BaseInsert)-1, 2);
@@ -1644,7 +1642,7 @@ begin
             if not IsFirstRowInChunk then
               Row := Row + ','+CRLF+#9+'(';
             for i:=0 to Data.ColumnCount-1 do begin
-              if not ColumnList[i].Virtuality.IsEmpty then
+              if Data.ColIsVirtual(i) then
                 Continue;
               if Data.IsNull(i) then
                 Row := Row + 'NULL'