00001 //# ExprAggrNode.h: TaQL node representing a scalar aggregate function 00002 //# Copyright (C) 2013 00003 //# Associated Universities, Inc. Washington DC, USA. 00004 //# 00005 //# This library is free software; you can redistribute it and/or modify it 00006 //# under the terms of the GNU Library General Public License as published by 00007 //# the Free Software Foundation; either version 2 of the License, or (at your 00008 //# option) any later version. 00009 //# 00010 //# This library is distributed in the hope that it will be useful, but WITHOUT 00011 //# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 00012 //# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public 00013 //# License for more details. 00014 //# 00015 //# You should have received a copy of the GNU Library General Public License 00016 //# along with this library; if not, write to the Free Software Foundation, 00017 //# Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA. 00018 //# 00019 //# Correspondence concerning AIPS++ should be addressed as follows: 00020 //# Internet email: aips2-request@nrao.edu. 00021 //# Postal address: AIPS++ Project Office 00022 //# National Radio Astronomy Observatory 00023 //# 520 Edgemont Road 00024 //# Charlottesville, VA 22903-2475 USA 00025 //# 00026 //# $Id: TaQLNode.h 21051 2011-04-20 11:46:29Z gervandiepen $ 00027 00028 #ifndef TABLES_EXPRAGGRNODE_H 00029 #define TABLES_EXPRAGGRNODE_H 00030 00031 //# Includes 00032 #include <casacore/casa/aips.h> 00033 #include <casacore/tables/TaQL/ExprFuncNode.h> 00034 00035 00036 namespace casacore { //# NAMESPACE CASACORE - BEGIN 00037 00038 //# Forward Declarations. 00039 class TableExprGroupFuncBase; 00040 class TableExprGroupFuncSet; 00041 00042 // <summary> 00043 // TaQL node representing a scalar aggregate function 00044 // </summary> 00045 00046 // <use visibility=local> 00047 00048 // <reviewed reviewer="" date="" tests="tTableGram"> 00049 // </reviewed> 00050 00051 // <synopsis> 00052 // A TableExprAggrNode object is a special TableExprFuncNode object. 00053 // Instead of operating on a single row, it operates on a group of table 00054 // rows, usually formed by means of the GROUPBY clause. 00055 // It aggregates the values in the rows in the group by means of an 00056 // aggregation function derived from TableExprGroupFuncBase. 00057 // Several standard aggregation functions (e.g., gmean, gmin, gsum) are 00058 // defined in TaQL and implemented this way. 00059 // 00060 // There are two types of aggregate function implementations: 00061 // <ul> 00062 // <li> Immediate aggregate functions calculate the results while the 00063 // groups are being formed. In this way they step sequentially through 00064 // the data. 00065 // This is only possible for functions that do not have to keep 00066 // to many data in memory. 00067 // <li> Lazy aggregate functions calculate the results after the groups are 00068 // formed using the vector of TableExprIds they get per group. 00069 // In this way only data for a single group might need to be kept in 00070 // memory. It is used, for instance, to calculate the median. 00071 // </ul> 00072 // Note that this class handles operands that are a scalar or array. 00073 // If array, all values in the array are used as individual values. 00074 // Class TableExprAggrNodeArray handles aggregate functions giving an 00075 // array result (e.g., function <src>gaggr</src>). 00076 // 00077 // It is also possible to define an aggregate function in a UDF derived 00078 // from class UDFBase. Such an aggregate function is instantiated as a 00079 // TableExprUDFNode(Array) object, not as TabeExprAggrNode(Array). 00080 // These functions are always lazy. 00081 // </synopsis> 00082 00083 class TableExprAggrNode: public TableExprFuncNode 00084 { 00085 public: 00086 // Constructor. 00087 TableExprAggrNode (FunctionType, NodeDataType, ValueType, 00088 const TableExprNodeSet& source); 00089 00090 // Check the operands of the aggregate function and return the 00091 // result's data type. 00092 static NodeDataType checkOperands (Block<Int>& dtypeOper, 00093 ValueType& resVT, FunctionType ftype, 00094 PtrBlock<TableExprNodeRep*>& nodes); 00095 00096 // Get the nodes representing an aggregate function. 00097 virtual void getAggrNodes (vector<TableExprNodeRep*>& aggr); 00098 00099 // Get the operand node. 00100 TableExprNodeRep* operand() 00101 { return (operands().empty() ? 0 : operands()[0]); } 00102 00103 // Create the correct aggregate function object. 00104 // It is also kept in case it is a lazy aggregate function. 00105 virtual CountedPtr<TableExprGroupFuncBase> makeGroupAggrFunc(); 00106 00107 // Is the aggregate function a lazy or an immediate one? 00108 virtual Bool isLazyAggregate() const; 00109 00110 // Functions to get the result of an aggregate function. 00111 // <group> 00112 virtual Bool getBool (const TableExprId& id); 00113 virtual Int64 getInt (const TableExprId& id); 00114 virtual Double getDouble (const TableExprId& id); 00115 virtual DComplex getDComplex (const TableExprId& id); 00116 virtual String getString (const TableExprId& id); 00117 virtual MVTime getDate (const TableExprId& id); 00118 // </group> 00119 00120 private: 00121 // Do the actual creation of the correct aggregate function object. 00122 TableExprGroupFuncBase* doMakeGroupAggrFunc(); 00123 00124 //# Data members. 00125 CountedPtr<TableExprGroupFuncBase> itsFunc; 00126 }; 00127 00128 00129 } //# NAMESPACE CASACORE - END 00130 00131 #endif