Make the Transform read from an EnrichedDocumentsBatchReader

milli/src/documents/enriched.rs

@@ -0,0 +1,103 @@
+use std::fs::File;
+use std::{io, str};
+
+use obkv::KvReader;
+
+use super::{
+    DocumentsBatchCursor, DocumentsBatchCursorError, DocumentsBatchIndex, DocumentsBatchReader,
+    Error,
+};
+use crate::FieldId;
+
+/// The `EnrichedDocumentsBatchReader` provides a way to iterate over documents that have
+/// been created with a `DocumentsBatchWriter` and, for the enriched data,
+/// a simple `grenad::Reader<File>`.
+///
+/// The documents are returned in the form of `obkv::Reader` where each field is identified with a
+/// `FieldId`. The mapping between the field ids and the field names is done thanks to the index.
+pub struct EnrichedDocumentsBatchReader<R> {
+    documents: DocumentsBatchReader<R>,
+    external_ids: grenad::ReaderCursor<File>,
+}
+
+impl<R: io::Read + io::Seek> EnrichedDocumentsBatchReader<R> {
+    pub fn new(
+        documents: DocumentsBatchReader<R>,
+        external_ids: grenad::Reader<File>,
+    ) -> Result<Self, Error> {
+        if documents.documents_count() as u64 == external_ids.len() {
+            Ok(EnrichedDocumentsBatchReader {
+                documents,
+                external_ids: external_ids.into_cursor()?,
+            })
+        } else {
+            Err(Error::InvalidEnrichedData)
+        }
+    }
+
+    pub fn documents_count(&self) -> u32 {
+        self.documents.documents_count()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.documents.is_empty()
+    }
+
+    pub fn documents_batch_index(&self) -> &DocumentsBatchIndex {
+        self.documents.documents_batch_index()
+    }
+
+    /// This method returns a forward cursor over the enriched documents.
+    pub fn into_cursor(self) -> EnrichedDocumentsBatchCursor<R> {
+        let EnrichedDocumentsBatchReader { documents, mut external_ids } = self;
+        external_ids.reset();
+        EnrichedDocumentsBatchCursor { documents: documents.into_cursor(), external_ids }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct EnrichedDocument<'a> {
+    pub document: KvReader<'a, FieldId>,
+    pub external_id: &'a str,
+}
+
+pub struct EnrichedDocumentsBatchCursor<R> {
+    documents: DocumentsBatchCursor<R>,
+    external_ids: grenad::ReaderCursor<File>,
+}
+
+impl<R> EnrichedDocumentsBatchCursor<R> {
+    pub fn into_reader(self) -> EnrichedDocumentsBatchReader<R> {
+        let EnrichedDocumentsBatchCursor { documents, external_ids } = self;
+        EnrichedDocumentsBatchReader { documents: documents.into_reader(), external_ids }
+    }
+
+    pub fn documents_batch_index(&self) -> &DocumentsBatchIndex {
+        self.documents.documents_batch_index()
+    }
+
+    /// Resets the cursor to be able to read from the start again.
+    pub fn reset(&mut self) {
+        self.documents.reset();
+        self.external_ids.reset();
+    }
+}
+
+impl<R: io::Read + io::Seek> EnrichedDocumentsBatchCursor<R> {
+    /// Returns the next document, starting from the first one. Subsequent calls to
+    /// `next_document` advance the document reader until all the documents have been read.
+    pub fn next_enriched_document(
+        &mut self,
+    ) -> Result<Option<EnrichedDocument>, DocumentsBatchCursorError> {
+        let document = self.documents.next_document()?;
+        let external_id = match self.external_ids.move_on_next()? {
+            Some((_, bytes)) => Some(str::from_utf8(bytes)?),
+            None => None,
+        };
+
+        match document.zip(external_id) {
+            Some((document, external_id)) => Ok(Some(EnrichedDocument { document, external_id })),
+            None => Ok(None),
+        }
+    }
+}