casacore
TableExprIdAggr.h
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1//# TableExprIdAggr.h: The Table Expression Selection id used with aggregation
2//# Copyright (C) 2013
3//# Associated Universities, Inc. Washington DC, USA.
4//#
5//# This library is free software; you can redistribute it and/or modify it
6//# under the terms of the GNU Library General Public License as published by
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8//# option) any later version.
9//#
10//# This library is distributed in the hope that it will be useful, but WITHOUT
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26//#
27//# $Id: TableExprId.h 21403 2013-12-03 20:51:02Z gervandiepen $
28
29
30#ifndef TABLES_TABLEEXPRIDAGGR_H
31#define TABLES_TABLEEXPRIDAGGR_H
32
33//# Includes
34#include <casacore/casa/aips.h>
35#include <casacore/tables/TaQL/TableExprId.h>
36#include <casacore/tables/TaQL/ExprGroup.h>
37#include <casacore/casa/Utilities/CountedPtr.h>
38#include <casacore/casa/Utilities/Assert.h>
39#include <casacore/casa/Exceptions/Error.h>
40
41namespace casacore { //# NAMESPACE CASACORE - BEGIN
42
43 // <summary>
44 // The Table Expression Selection id used with aggregation
45 // </summary>
46
47 // <use visibility=export>
48
49 // <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="tExprGroup">
50 // </reviewed>
51
52 // <synopsis>
53 // This class provides the user the ability to identify the data objects
54 // to test in a TaQL expression using aggregate functions.
55 // <br>
56 // It adds a TableExprGroupResult object to the TableExprId class which
57 // is used by the various classes derived from TableExprGroupFuncBase
58 // to get or evaluate the aggregated value.
59 // An aggregated value can be determined in two ways:
60 // <ul>
61 // <li> An immediate aggregate function has calculated its value in its
62 // <src>apply</src> function.
63 // Each group has a TableExprGroupFuncSet containing the values
64 // of all immediate aggregate functions of that group.
65 // A vector of these objects is part of of TableExprGroupResult
66 // and is used by the TableExprAggrNode(Array) <src>get</src> functions
67 // to return the correct value.
68 // <li> A lazy aggregate function calculates the value as part of its
69 // <src>get</src> function. It uses the vector of TableExprId objects
70 // in TableExprGroupResult to know which rows (or records) belong to
71 // which group. Note that UDF aggregate functions are always lazy.
72 // </ul>
73 // TableExprIdAggr contains a static function to (statically) cast a
74 // TableExprId object to TableExprIdAggr. A magic value is used to check
75 // that the cast is valid.
76 // <br>No dynamic_cast is used, because it requires TableExprId to contain
77 // virtual functions making the object larger. TaQL can hold quite large
78 // vectors of TableExprId objects, so such overhead is unacceptably large.
79 // </synopsis>
80
81 // <motivation>
82 // This class makes it possible to retrieve aggregated values using the
83 // standard <src>get</src> functions taking an TableExprId.
84 // </motivation>
85
87 {
88 public:
89 // Construct it from the aggregation results.
91 : itsMagicValue (0xabababab),
93 {}
94
95 // Get out the aggregation result object.
97 { return *itsResult; }
98
99 // Get the magic value (to check if correct).
101 { return itsMagicValue; }
102
103 // Cast a TableExprId object to TableExprIdAggr. It checks if the cast
104 // is correct by checking the magic value.
105 static const TableExprIdAggr& cast (const TableExprId& id)
106 {
107 const TableExprIdAggr& idAggr = reinterpret_cast<const TableExprIdAggr&>(id);
108 AlwaysAssert (idAggr.getMagicValue() == 0xabababab, AipsError);
109 return idAggr;
110 }
111
112 private:
115 };
116
117
118} //# NAMESPACE CASACORE - END
119
120#endif
#define AlwaysAssert(expr, exception)
These marcos are provided for use instead of simply using the constructors of assert_ to allow additi...
Definition: Assert.h:157
Referenced counted pointer for constant data.
Definition: CountedPtr.h:81
Class holding the results of groupby and aggregation.
Definition: ExprGroup.h:145
CountedPtr< TableExprGroupResult > itsResult
TableExprIdAggr(const CountedPtr< TableExprGroupResult > &result)
Construct it from the aggregation results.
static const TableExprIdAggr & cast(const TableExprId &id)
Cast a TableExprId object to TableExprIdAggr.
uInt getMagicValue() const
Get the magic value (to check if correct).
const TableExprGroupResult & result() const
Get out the aggregation result object.
this file contains all the compiler specific defines
Definition: mainpage.dox:28
unsigned int uInt
Definition: aipstype.h:51