Open a BTree index reader from a FileRead and file metadata. Only reads footer, index block, and null bitmap on open. Data blocks are read on demand during queries.
(
reader: Box<dyn FileRead>,
file_size: u64,
meta: &BTreeIndexMeta,
key_comparator: F,
)
| 48 | /// Only reads footer, index block, and null bitmap on open. |
| 49 | /// Data blocks are read on demand during queries. |
| 50 | pub async fn open( |
| 51 | reader: Box<dyn FileRead>, |
| 52 | file_size: u64, |
| 53 | meta: &BTreeIndexMeta, |
| 54 | key_comparator: F, |
| 55 | ) -> io::Result<Self> { |
| 56 | if file_size < BTREE_FOOTER_ENCODED_LENGTH as u64 { |
| 57 | return Err(io::Error::new( |
| 58 | io::ErrorKind::InvalidData, |
| 59 | "File too small for BTree footer", |
| 60 | )); |
| 61 | } |
| 62 | |
| 63 | // 1. Read footer (last 52 bytes) |
| 64 | let footer_start = file_size - BTREE_FOOTER_ENCODED_LENGTH as u64; |
| 65 | let footer_bytes = reader |
| 66 | .read(footer_start..file_size) |
| 67 | .await |
| 68 | .map_err(|e| io::Error::other(e.to_string()))?; |
| 69 | let footer = BTreeFileFooter::read_footer(&footer_bytes)?; |
| 70 | |
| 71 | // 2. Read index block |
| 72 | let idx = &footer.index_block_handle; |
| 73 | let idx_end = idx.offset + idx.full_block_size() as u64; |
| 74 | let index_bytes = reader |
| 75 | .read(idx.offset..idx_end) |
| 76 | .await |
| 77 | .map_err(|e| io::Error::other(e.to_string()))?; |
| 78 | let index_block = read_block_from_bytes(&index_bytes, idx.size)?; |
| 79 | let sst_reader = SstFileReader::from_index_block(index_block); |
| 80 | |
| 81 | // 3. Read null bitmap |
| 82 | let null_bitmap = match &footer.null_bitmap_handle { |
| 83 | Some(h) => read_null_bitmap(reader.as_ref(), h).await?, |
| 84 | None => RoaringTreemap::new(), |
| 85 | }; |
| 86 | |
| 87 | Ok(Self { |
| 88 | reader, |
| 89 | sst_reader, |
| 90 | null_bitmap, |
| 91 | min_key: meta.first_key.clone(), |
| 92 | max_key: meta.last_key.clone(), |
| 93 | key_comparator, |
| 94 | }) |
| 95 | } |
| 96 | |
| 97 | /// Get the null bitmap (row ids of null keys). |
| 98 | pub fn null_bitmap(&self) -> &RoaringTreemap { |
no test coverage detected