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.\"
.IX Title "Aggregate 3pm"
.TH Aggregate 3pm "2020-07-07" "Lire 2.1.1" "LogReport's Lire Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Lire::Aggregate \- Base class for all operators that compute values from a group
of DLF records
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Lire::Aggregate;
\&
\&    use base qw/ Lire::Aggregate /;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The Lire::Aggregate is the base class of all operators that computes
values from a group of \s-1DLF\s0 records. These are the operators that are
used inside aggregators.
.PP
This package also defines most of the classes that represents the
group operators available in Lire report specification.
.SH "METHODS FOR SUBCLASSES OF Aggregate"
.IX Header "METHODS FOR SUBCLASSES OF Aggregate"
.ie n .SS "init( %params )"
.el .SS "init( \f(CW%params\fP )"
.IX Subsection "init( %params )"
Two supplemental parameters are needed for Aggregates:
.IP "parent" 4
.IX Item "parent"
The Lire::Aggregator which contain this Aggregate.
.IP "name" 4
.IX Item "name"
The identifier that can be used to find this operator in the report
specification. It will be returned by the \fBname()\fR method.
.ie n .SS "print( $fh, $prefix)"
.el .SS "print( \f(CW$fh\fP, \f(CW$prefix\fP)"
.IX Subsection "print( $fh, $prefix)"
This methods implements the \fBprint()\fR method required by
Lire::ReportOperator. It prints an empty \s-1XML\s0 element named after \fBop()\fR.
It also takes care of writing the name and label attributes. Other
attributes can be added to the \s-1XML\s0 element by overriding the
\&\fBxml_attrs()\fR method.
.SS "\fBxml_attrs()\fP"
.IX Subsection "xml_attrs()"
This method can be used to write additional \s-1XML\s0 attributes. The
returned string will be output in the \s-1XML\s0 element.
.ie n .SS "set_name( $name )"
.el .SS "set_name( \f(CW$name\fP )"
.IX Subsection "set_name( $name )"
Changes this operator's name.
.ie n .SS "create_numerical_info( $group_info )"
.el .SS "create_numerical_info( \f(CW$group_info\fP )"
.IX Subsection "create_numerical_info( $group_info )"
Subclass must implement this method.
.PP
The \f(CW$group_info\fR parameter is a Lire::Report::GroupInfo object to which
the operator implementation should add the appropriate ColumnInfo object to 
represent the data generated by the aggregate.
.ie n .SS "build_query( $query )"
.el .SS "build_query( \f(CW$query\fP )"
.IX Subsection "build_query( $query )"
\&\s-1FIXME.\s0
.PP
Provides a default implementation of build_query
.ie n .SS "set_missing_cases_aggr_expr( $query )"
.el .SS "set_missing_cases_aggr_expr( \f(CW$query\fP )"
.IX Subsection "set_missing_cases_aggr_expr( $query )"
Adds the aggregate expression to compute the number of missing cases
based on the required fields returned by the \fBsql_required_fields()\fR
method.
.PP
The method \fBset_missing_cases_value()\fR can be used to set the value from
the returned \s-1DLF\s0 row.
.ie n .SS "set_missing_cases_value( $row, $value )"
.el .SS "set_missing_cases_value( \f(CW$row\fP, \f(CW$value\fP )"
.IX Subsection "set_missing_cases_value( $row, $value )"
Sets the missing-cases value in \f(CW$value\fR to the value computed by the
expression sets using \fBset_missing_cases_aggr_expr()\fR.
.SS "\fBsql_aggr_expr()\fP"
.IX Subsection "sql_aggr_expr()"
Method used by the default implementation of \fBbuild_query()\fR. It should
return the \s-1SQL\s0 agregate expression that should be associated to this
Aggregate's name. For example, a simple Count implementation could
have returned 'count(*)' here.
.SS "\fBsql_required_fields()\fP"
.IX Subsection "sql_required_fields()"
Method used by the \fBset_missing_cases_aggr_expr()\fR to sets an aggregate
expression that will return the number of missing cases for this
aggregate. It should returns a list of fields that will create a
missing case when a value is \s-1NULL.\s0
.ie n .SS "create_value( $parent_group, $row )"
.el .SS "create_value( \f(CW$parent_group\fP, \f(CW$row\fP )"
.IX Subsection "create_value( $parent_group, $row )"
Method that is used by Aggregator when building the report table. The
report should return an hash reference with the appropriate keys set.
Consult \fBLire::Report::Entry\fR\|(3pm) for details.
.PP
The \f(CW$parent_group\fR parameter is the Lire::Report::Group to which the
value is added. This will be the table or containing group for values
added to Entries, and it will be the Group's parent when creating a
summary value.
.PP
The \f(CW$row\fR parameter is an hash ref containing the DlfResult row for
which the value should be created.
.PP
Implementation should use the \fBset_missing_cases_value()\fR method to set
the value's 'missing_cases' attribute.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBLire::ReportSpec\fR\|(3pm), \fBLire::ReportOperator\fR\|(3pm), \fBLire::Aggregator\fR\|(3pm).
.SH "AUTHORS"
.IX Header "AUTHORS"
.Vb 2
\&  Francis J. Lacoste <flacoste@logreport.org>
\&  Wolfgang Sourdeau <wolfgang@logreport.org>
.Ve
.SH "VERSION"
.IX Header "VERSION"
\&\f(CW$Id:\fR Aggregate.pm,v 1.16 2006/07/23 13:16:27 vanbaal Exp $
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2001\-2003 Stichting LogReport Foundation LogReport@LogReport.org
.PP
This file is part of Lire.
.PP
Lire is free software; you can redistribute it and/or modify
it under the terms of the \s-1GNU\s0 General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
.PP
This program is distributed in the hope that it will be useful,
but \s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the
\&\s-1GNU\s0 General Public License for more details.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License
along with this program (see \s-1COPYING\s0); if not, check with
http://www.gnu.org/copyleft/gpl.html.