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=encoding utf8

=head1 NAME

Lucy::Index::SegWriter - Write one segment of an index.

=head1 DESCRIPTION

SegWriter is a conduit through which information fed to Indexer passes.  It
manages L<Segment|Lucy::Index::Segment> and Inverter, invokes the
L<Analyzer|Lucy::Analysis::Analyzer> chain, and feeds low
level L<DataWriters|Lucy::Index::DataWriter> such as
PostingListWriter and DocWriter.

The sub-components of a SegWriter are determined by
L<Architecture|Lucy::Plan::Architecture>.  DataWriter components
which are added to the stack of writers via L<add_writer()|/add_writer> have
Add_Inverted_Doc() invoked for each document supplied to SegWriter’s
L<add_doc()|/add_doc>.

=head1 METHODS

=head2 register

    $seg_writer->register(
        api       => $api,        # required
        component => $component,  # required
    );

Register a DataWriter component with the SegWriter.  (Note that
registration simply makes the writer available via L<fetch()|/fetch>, so you may
also want to call L<add_writer()|/add_writer>).

=over

=item *

B<api> - The name of the DataWriter api which C<writer>
implements.

=item *

B<component> - A DataWriter.

=back

=head2 fetch

    my $obj = $seg_writer->fetch($api);

Retrieve a registered component.

=over

=item *

B<api> - The name of the DataWriter api which the component
implements.

=back

=head2 add_writer

    $seg_writer->add_writer($writer);

Add a DataWriter to the SegWriter’s stack of writers.

=head2 add_doc

    $seg_writer->add_doc(
        doc   => $doc,    # required
        boost => $boost,  # default: 1.0
    );

Add a document to the segment.  Inverts C<doc>, increments
the Segment’s internal document id, then calls Add_Inverted_Doc(),
feeding all sub-writers.

=head2 add_segment

    $seg_writer->add_segment(
        reader  => $reader,   # required
        doc_map => $doc_map,  # default: undef
    );

Add content from an existing segment into the one currently being
written.

=over

=item *

B<reader> - The SegReader containing content to add.

=item *

B<doc_map> - An array of integers mapping old document ids to
new.  Deleted documents are mapped to 0, indicating that they should be
skipped.

=back

=head2 finish

    $seg_writer->finish();

Complete the segment: close all streams, store metadata, etc.

=head1 INHERITANCE

Lucy::Index::SegWriter isa L<Lucy::Index::DataWriter> isa Clownfish::Obj.

=cut

