public override bool CanAlterColumn(IPlatformTableSourceColumnInfo existingColumn, IPlatformTableSourceColumnInfo newColumn,
out string errorMessage)
{
errorMessage = "";
//text -> : -- Cannot alter column 't' because it is 'text'.
//image -> -- Cannot alter column 'v' because it is 'image'.
// x -> CLOB (opposed to varchar2) -- Operand type clash: x is incompatible with text
// x -> BinaryData -- Operand type clash: x is incompatible with binarydata
// x -> datetime -- Operand type clash: x is incompatible with datetime
//datetime -> x except varchar -- Operand type clash: datetime is incompatible with x
// Data type conversions
if (existingColumn.DataType.Type == DBDataType.TEXT && existingColumn.DataType.Length > PlatformDataTypeInfo.VARCHAR_MAXLENGTH &&
newColumn.DataType.Type == DBDataType.TEXT && newColumn.DataType.Length < PlatformDataTypeInfo.VARCHAR_MAXLENGTH)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, true) +
string.Format(" This is because the column was previously defined with a length greater than {0}.",
PlatformDataTypeInfo.VARCHAR_MAXLENGTH);
return(false);
}
if (existingColumn.DataType.Type == DBDataType.BINARY_DATA)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, true);
return(false);
}
if (newColumn.DataType.Type == DBDataType.TEXT && newColumn.DataType.Length > PlatformDataTypeInfo.VARCHAR_MAXLENGTH)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, false) +
string.Format(" This is because the column is now defined with a length greater than {0}.",
PlatformDataTypeInfo.VARCHAR_MAXLENGTH);
return(false);
}
if (newColumn.DataType.Type.IsOneOf(DBDataType.BINARY_DATA, DBDataType.DATE_TIME))
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, false);
return(false);
}
if (existingColumn.DataType.Type == DBDataType.DATE_TIME && newColumn.DataType.Type != DBDataType.TEXT)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, false);
return(false);
}
// Autonumber conversions
if (existingColumn.IsAutoGenerated && !newColumn.IsAutoGenerated)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn.TableSource.Name, existingColumn.Name, "Autonumber", existingColumn.DataType.Type.ToText(), newColumn.DataType.SqlDataType, newColumn.DataType.Type.ToText(), true);
return(false);
}
if (!existingColumn.IsAutoGenerated && newColumn.IsAutoGenerated)
{
// Change is allowed if the table is empty
bool hasRows;
using (IDbConnection conn = DatabaseServices.TransactionService.CreateConnection()) {
using (IDbCommand cmd = DatabaseServices.ExecutionService.CreateCommand(conn,
"select count(1) from " + Identifiers.EscapeAndQualifyIdentifierForLocalDatabase(existingColumn.TableSource.Name))) {
hasRows = Convert.ToInt32(cmd.ExecuteScalar()) > 0;
}
}
if (hasRows)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn.TableSource.Name, existingColumn.Name,
existingColumn.DataType.SqlDataType, existingColumn.DataType.Type.ToText(), "Autonumber",
newColumn.DataType.Type.ToText(), false);
return(false);
}
}
return(true);
}
public override bool CanAlterColumn(IPlatformTableSourceColumnInfo existingColumn, IPlatformTableSourceColumnInfo newColumn,
out string errorMessage)
{
errorMessage = "";
if (newColumn.IsAutoGenerated && newColumn.IsPrimaryKey == false)
{
errorMessage = string.Format("Column {0} of table {1} can't be Auto Number if it's not the identifier of the entity.", newColumn.Name, newColumn.TableSource.Name);
return(false);
}
// Data type conversions
if (existingColumn.DataType.Type == DBDataType.TEXT && existingColumn.DataType.Length > MySQLPlatformDataTypeInfo.VARCHAR_MAXLENGTH &&
newColumn.DataType.Type == DBDataType.TEXT && newColumn.DataType.Length < MySQLPlatformDataTypeInfo.VARCHAR_MAXLENGTH)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, true) +
string.Format(" This is because the column was previously defined with a length greater than {0}.",
MySQLPlatformDataTypeInfo.VARCHAR_MAXLENGTH);
return(false);
}
if (existingColumn.DataType.Type == DBDataType.BINARY_DATA)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, true);
return(false);
}
if (newColumn.DataType.Type.IsOneOf(DBDataType.BINARY_DATA, DBDataType.DATE_TIME))
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, false);
return(false);
}
if (existingColumn.DataType.Type == DBDataType.DATE_TIME && newColumn.DataType.Type != DBDataType.TEXT)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn, newColumn, false);
return(false);
}
// Autonumber conversions
if (existingColumn.IsAutoGenerated && !newColumn.IsAutoGenerated)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn.TableSource.Name, existingColumn.Name, "Autonumber", existingColumn.DataType.Type.ToText(), newColumn.DataType.SqlDataType, newColumn.DataType.Type.ToText(), true);
return(false);
}
if (!existingColumn.IsAutoGenerated && newColumn.IsAutoGenerated)
{
// Change is allowed if the table is empty
bool hasRows;
using (IDbConnection conn = DatabaseServices.TransactionService.CreateConnection()) {
using (IDbCommand cmd = DatabaseServices.ExecutionService.CreateCommand(conn,
"select count(1) from " + Identifiers.EscapeAndQualifyIdentifierForLocalDatabase(existingColumn.TableSource.Name))) {
hasRows = Convert.ToInt32(cmd.ExecuteScalar()) > 0;
}
}
if (hasRows)
{
errorMessage = GetColumnCannotBeChangedMessage(existingColumn.TableSource.Name, existingColumn.Name,
existingColumn.DataType.SqlDataType, existingColumn.DataType.Type.ToText(), "Autonumber",
newColumn.DataType.Type.ToText(), false);
return(false);
}
}
return(true);
}