Lucy::...aWriter(3pm)

💖 Lucy::Index::DataWriter — the manual page, but make it a group chat 💖

okay bestie, so this page lives in the User Contributed Perl Documentation collection, and it's about Lucy::Index::DataWriter, which is literally the abstract blueprint for writing data into an index. Buckle up, it's giving "backend internals but make it cute". 🎀

---

✨ NAME ✨

Lucy::Index::DataWriter — Write data to an index. no cap, that's the whole job. 💅

---

✨ SYNOPSIS ✨

# Abstract base class.

that's it. that's the synopsis. she's abstract, she doesn't do anything by herself, she's a concept. main character energy but uninstantiable. 👑

---

✨ DESCRIPTION ✨

So DataWriter is an abstract base class for writing index data, generally in segment-sized chunks. 🧩

Every single component of an index — think stored fields, lexicon, postings, deletions — gets its own lil DataWriter/DataReader pair. it's giving "couples costume but for data structures". 🫶

And here's the fun part: components may be specified per index by subclassing Architecture. iykyk. 🌸

---

✨ CONSTRUCTORS ✨

🌈 new

my $writer = MyDataWriter->new(
    snapshot   => $snapshot,      # required
    segment    => $segment,       # required
    polyreader => $polyreader,    # required
);

Abstract constructor. she does not exist in the flesh, only in spirit. 💀

• snapshot — The Snapshot that will be committed at the end of the indexing session. required, bestie, don't forget her.
• segment — The Segment in progress. also required. she's mid-transformation, let her cook. 🔥
• polyreader — A PolyReader representing all existing data in the index. (If the index is brand new, the PolyReader will have no sub-readers — she's fresh out the box, no history, baby's first index. 👶) required.

---

✨ ABSTRACT METHODS ✨

these ones? you must implement them. no skipping. periodt.

🦋 add_segment

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

Add content from an existing segment into the one currently being written. it's a glow-up merge, she's absorbing her ex's data. 💅

• reader — The SegReader containing content to add.
• doc_map — An array of integers mapping old document ids to new ones. Deleted documents get mapped to 0, which is the signal that they should be skipped. bye felicia. 👋

🦋 finish

$data_writer->finish();

Complete the segment: close all streams, store metadata, etc. wrap it up, she's done, mic drop. 🎤

🦋 format

my $int = $data_writer->format();

Every writer must specify a file format revision number, and that number should increment every time the format changes. and who's in charge of actually checking that revision? not her. 👀 Responsibility for revision checking is left to the companion DataReader. she said "that's not my job, ask my friend". 💖

---

✨ METHODS ✨

🍓 delete_segment

$data_writer->delete_segment($reader);

Remove a segment's data. the default implementation is a no-op, because all files within the segment directory get automatically deleted anyway. so like, why bother. 💅

Subclasses which manage their own files outside of the segment system should override this method and use it as a trigger for cleaning up obsolete data. if you're storing files somewhere weird, that's on you, bestie. 🧹

• reader — The SegReader containing content to merge, which must represent a segment which is part of the current snapshot.

🍓 merge_segment

$data_writer->merge_segment(
    reader  => $reader,   # required
    doc_map => $doc_map,  # default: undef
);

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

The default implementation calls add_segment() then delete_segment(). two-for-one special, she's efficient like that. 😌

• reader — The SegReader containing content to merge, which must represent a segment which is part of the current snapshot.
• doc_map — An array of integers mapping old document ids to new. Deleted documents are mapped to 0, indicating that they should be skipped.

🍓 metadata

my $hashref = $data_writer->metadata();

Arbitrary metadata to be serialized and stored by the Segment. the default implementation supplies a hash with a single key-value pair for "format". simple. elegant. minimal. she ate and left no crumbs. 🎀

🍓 get_snapshot

my $snapshot = $data_writer->get_snapshot();

Accessor for the "snapshot" member var. 🔑

🍓 get_segment

my $segment = $data_writer->get_segment();

Accessor for the "segment" member var. 🔑

🍓 get_polyreader

my $poly_reader = $data_writer->get_polyreader();

Accessor for the "polyreader" member var. 🔑

🍓 get_schema

my $schema = $data_writer->get_schema();

Accessor for the "schema" member var. 🔑

🍓 get_folder

my $folder = $data_writer->get_folder();

Accessor for the "folder" member var. 🔑

look at all those accessors. she's got getters for days. 🌈

---

✨ INHERITANCE ✨

Lucy::Index::DataWriter isa Clownfish::Obj. family tree iconic, lineage immaculate. 👑

---

and that's the whole page, bestie!! this was perl v5.42.0, dated 2025-07-25, straight from the User Contributed Perl Documentation archives. you understood all of it, obviously, because you're that girl. slay, go write an index. 💜🦋✨