public override DataTable GetSchemaTable()
{
if (metadata != null)
return metadata;
#if DEBUG
System.Diagnostics.Trace.WriteLine("NuoDbDataReader.GetSchemaTable(" + statement.CommandText + ")");
#endif
EncodedDataStream dataStream = new EncodedDataStream();
dataStream.startMessage(Protocol.GetMetaData);
dataStream.encodeInt(handle);
connection.InternalConnection.sendAndReceive(dataStream);
int numberColumns = dataStream.getInt();
metadata = new DataTable("SchemaTable");
// Info on the schema of this table is at http://msdn.microsoft.com/en-us/library/system.data.odbc.odbcdatareader.getschematable.aspx
// The zero-based ordinal of the column. This column cannot contain a null value.
metadata.Columns.Add("ColumnOrdinal", typeof(int));
// The name of the column; this might not be unique. If the column name cannot be determined, a null value is returned.
// This name always reflects the most recent naming of the column in the current view or command text.
metadata.Columns.Add("ColumnName", typeof(string));
// The maximum possible length of a value in the column. For columns that use a fixed-length data type, this is the size of the data type.
metadata.Columns.Add("ColumnSize", typeof(int));
// If DbType is a numeric data type, this is the maximum precision of the column. The precision depends on the
// definition of the column. If DbType is not a numeric data type, do not use the data in this column.
// If the underlying ODBC driver returns a precision value for a non-numeric data type, this value is used in the schema table.
metadata.Columns.Add("NumericPrecision", typeof(int));
// If DbType is Decimal, the number of digits to the right of the decimal point. Otherwise, this is a null value.
// If the underlying ODBC driver returns a precision value for a non-numeric data type, this value is used in the schema table.
metadata.Columns.Add("NumericScale", typeof(int));
// The name of the catalog in the data store that contains the column. NULL if the base catalog name cannot be determined.
// The default for this column is a null value.
metadata.Columns.Add("BaseCatalogName", typeof(string));
// The name of the schema in the data source that contains the column. NULL if the base catalog name cannot be determined.
// The default for this column is a null value.
metadata.Columns.Add("BaseSchemaName", typeof(string));
// The name of the table or view in the data store that contains the column. A null value if the base table name cannot be determined.
// The default of this column is a null value.
metadata.Columns.Add("BaseTableName", typeof(string));
// The name of the column in the data store. This might be different from the column name returned in the ColumnName column if an alias was used.
// A null value if the base column name cannot be determined or if the rowset column is derived, but not identical to, a column in the data store.
// The default for this column is a null value.
metadata.Columns.Add("BaseColumnName", typeof(string));
// Maps to the common language runtime type of DbType.
metadata.Columns.Add("DataType", typeof(Type));
// The underlying driver type.
metadata.Columns.Add("ProviderType", typeof(int));
// true if the column contains a Binary Long Object (BLOB) that contains very long data. The definition of very long data is driver-specific.
metadata.Columns.Add("IsLong", typeof(bool));
// true if the column assigns values to new rows in fixed increments; otherwise false. The default for this column is false.
metadata.Columns.Add("IsAutoIncrement", typeof(bool));
// true if the column cannot be modified; otherwise false.
metadata.Columns.Add("IsReadOnly", typeof(bool));
// true: No two rows in the base table (the table returned in BaseTableName) can have the same value in this column.
// IsUnique is guaranteed to be true if the column represents a key by itself or if there is a constraint of type UNIQUE that applies only to this column.
// false: The column can contain duplicate values in the base table. The default for this column is false.
metadata.Columns.Add("IsUnique", typeof(bool));
// true: The column is one of a set of columns in the rowset that, taken together, uniquely identify the row.
// The set of columns with IsKey set to true must uniquely identify a row in the rowset. There is no requirement that this set of columns is a minimal set of columns. This set of columns may be generated from a base table primary key, a unique constraint, or a unique index.
// false: The column is not required to uniquely identify the row.
metadata.Columns.Add("IsKey", typeof(bool));
// Set if the column contains a persistent row identifier that cannot be written to, and has no meaningful value except to identity the row.
metadata.Columns.Add("IsRowVersion", typeof(bool));
// true if the consumer can set the column to a null value or if the driver cannot determine whether the consumer can set the column to a null value.
// Otherwise, false. A column may contain null values, even if it cannot be set to a null value.
metadata.Columns.Add("AllowDBNull", typeof(bool));
// The SQLDataReader also returns these columns:
// Returns a string representing the data type of the specified column.
metadata.Columns.Add("DataTypeName", typeof(string));
// true: The column is an identity column.
// false: The column is not an identity column.
metadata.Columns.Add("IsIdentity", typeof(bool));
// true: The column is an expression column.
// false: The column is not an expression column.
metadata.Columns.Add("IsExpression", typeof(bool));
metadata.BeginLoadData();
for (int n = 0; n < numberColumns; ++n)
{
DataRow row = metadata.NewRow();
row["ColumnOrdinal"] = n;
// data fields must be read in this exact order!
row["BaseCatalogName"] = dataStream.getString();
row["BaseSchemaName"] = dataStream.getString();
row["BaseTableName"] = dataStream.getString();
row["BaseColumnName"] = dataStream.getString();
row["ColumnName"] = dataStream.getString();
string collationSequence = dataStream.getString();
row["DataTypeName"] = dataStream.getString();
row["ProviderType"] = NuoDbConnectionInternal.mapJavaSqlToDbType(dataStream.getInt());
row["ColumnSize"] = dataStream.getInt();
row["NumericPrecision"] = dataStream.getInt();
row["NumericScale"] = dataStream.getInt();
if (((DbType)row["ProviderType"] == DbType.Int16 || (DbType)row["ProviderType"] == DbType.Int32 || (DbType)row["ProviderType"] == DbType.Int64) &&
(int)row["NumericScale"] != 0)
{
row["ProviderType"] = DbType.Decimal;
}
row["DataType"] = Type.GetType(NuoDbConnectionInternal.mapNuoDbToNetType((string)row["DataTypeName"], (int)row["NumericPrecision"], (int)row["NumericScale"]));
int flags = dataStream.getInt();
const int rsmdSearchable = (1 << 1);
const int rsmdAutoIncrement = (1 << 2);
const int rsmdCaseSensitive = (1 << 3);
const int rsmdCurrency = (1 << 4);
const int rsmdDefinitelyWritable = (1 << 5);
const int rsmdWritable = (1 << 6);
const int rsmdReadOnly = (1 << 7);
const int rsmdSigned = (1 << 8);
const int rsmdNullable = (1 << 9);
row["IsAutoIncrement"] = (flags & rsmdAutoIncrement) != 0;
row["IsReadOnly"] = (flags & rsmdReadOnly) != 0;
row["AllowDBNull"] = (flags & rsmdNullable) != 0;
// for the moment, set the column to be a normal one; later we will look for primary indexes
row["IsKey"] = row["IsIdentity"] = row["IsUnique"] = false;
row["IsLong"] = row["IsRowVersion"] = row["IsExpression"] = false;
metadata.Rows.Add(row);
#if DEBUG
System.Diagnostics.Trace.WriteLine("-> " + row["ColumnName"] + ", " +
row["DataTypeName"] + "(" + row["NumericPrecision"] + "," + row["NumericScale"] + ") " +
row["DataType"]);
#endif
}
metadata.EndLoadData();
// fill in the IsPrimary column
Dictionary<string, DataTable> schemas = new Dictionary<string, DataTable>();
foreach (DataRow row in metadata.Rows)
{
string key = row["BaseSchemaName"] + "|" + row["BaseTableName"];
DataTable indexInfo = null;
if (!schemas.ContainsKey(key))
{
indexInfo = connection.GetSchema("IndexColumns", new string[] { null, (string)row["BaseSchemaName"], (string)row["BaseTableName"] });
schemas.Add(key, indexInfo);
}
else
indexInfo = schemas[key];
DataRow[] rows = indexInfo.Select(String.Format("INDEXCOLUMN_NAME = '{0}' AND INDEXCOLUMN_ISPRIMARY = true", row["BaseColumnName"]));
if (rows != null && rows.Length > 0)
{
row.BeginEdit();
row["IsKey"] = row["IsIdentity"] = true;
row.EndEdit();
}
}
return metadata;
}
