public override void FillTableSchema(DataTable table, string selectCommand, CommandParameterCollection parameters)
{
ClickHouseConnection clickHouseConnection = GetConnection() as ClickHouseConnection;
try
{
OpenConnection(clickHouseConnection);
selectCommand = PrepareSelectCommand(selectCommand, table.TableName, clickHouseConnection);
/*To reduce size of traffic and size of answer from ClickHouse server.
* Because FillSchema doesn't work in this ADO.NET library.
* LIMIT 0 gets an empy set, but we still have list of desired columns
* Prorably can be a better way.
*/
selectCommand += " LIMIT 0";
ClickHouseCommand clickHouseCommand = clickHouseConnection.CreateCommand();
foreach (CommandParameter p in parameters)
{
selectCommand = selectCommand.Replace($"@{p.Name}", $"{{{p.Name}:{(ClickHouseTypeCode)p.DataType}}}");
clickHouseCommand.AddParameter(p.Name, ((ClickHouseTypeCode)p.DataType).ToString(), p.Value);
}
clickHouseCommand.CommandText = selectCommand;
using (ClickHouseDataReader reader = clickHouseCommand.ExecuteReader() as ClickHouseDataReader)
{
var clms = GetColumns(reader);
table.Columns.AddRange(clms.ToArray());
}
}
finally
{
DisposeConnection(clickHouseConnection);
}
}
private IEnumerable <DataColumn> GetColumns(ClickHouseDataReader reader)
{
for (int i = 0; i < reader.FieldCount; i++)
{
var columnType = reader.GetFieldType(i);
yield return(new DataColumn(reader.GetName(i), columnType));
}
}
internal static ClickHouseType[] GetClickHouseColumnTypes(this ClickHouseDataReader reader)
{
var count = reader.FieldCount;
var names = new ClickHouseType[count];
for (int i = 0; i < count; i++)
{
names[i] = reader.GetClickHouseType(i);
}
return(names);
}
public static DataTable DescribeSchema(this ClickHouseDataReader reader)
{
var result = new DataTable();
foreach (var columnName in Columns)
{
result.Columns.Add(columnName);
}
for (int i = 0; i < reader.FieldCount; i++)
{
result.Rows.Add(reader.DescribeColumn(i));
}
return(result);
}
private static List <T> Scan <T>(IDbCommand cmd, Func <ClickHouseDataReader, T> read)
{
List <T> result = new List <T>();
using ClickHouseDataReader reader = (ClickHouseDataReader)cmd.ExecuteReader();
do
{
while (reader.Read())
{
result.Add(read.Invoke(reader));
}
} while (reader.NextResult());
return(result);
}
private static object[] DescribeColumn(this ClickHouseDataReader reader, int ordinal)
{
var chType = reader.GetClickHouseType(ordinal);
var result = new object[Columns.Length];
result[0] = reader.GetName(ordinal); // ColumnName
result[1] = ordinal; // ColumnOrdinal
result[2] = null; // ColumnSize
result[3] = null; // NumericPrecision
result[4] = null; // NumericScale
result[5] = chType.FrameworkType; // DataType
result[6] = chType.ToString(); // ProviderType
result[7] = chType.TypeCode == ClickHouseTypeCode.String; // IsLong
result[8] = chType.TypeCode == ClickHouseTypeCode.Nullable; // AllowDBNull
result[9] = true; // IsReadOnly
result[10] = false; // IsRowVersion
result[11] = false; // IsUnique
result[12] = false; // IsKey
result[13] = false; // IsAutoIncrement
result[14] = null; // BaseCatalogName
result[15] = null; // BaseSchemaName
result[16] = null; // BaseTableName
result[17] = reader.GetName(ordinal); // BaseColumnName
result[18] = null; // AutoIncrementSeed
result[19] = null; // AutoIncrementStep
result[20] = null; // DefaultValue
result[21] = null; // Expression
result[22] = MappingType.Element; // ColumnMapping
result[23] = null; // BaseTableNamespace
result[24] = null; // BaseColumnNamespace
if (chType is DecimalType dt)
{
result[2] = dt.Size;
result[3] = dt.Precision;
result[4] = dt.Scale;
}
return(result);
}
