From 8bfb1f9e9f74f41eb251eb025838244cc5c256eb Mon Sep 17 00:00:00 2001 From: Munyoki Kilyungi Date: Mon, 6 Feb 2023 14:32:27 +0300 Subject: Add method to fetch the current matrix * gn3/db/matrix.py: New file. Signed-off-by: Munyoki Kilyungi --- gn3/db/matrix.py | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 gn3/db/matrix.py (limited to 'gn3/db') diff --git a/gn3/db/matrix.py b/gn3/db/matrix.py new file mode 100644 index 0000000..d40f3c3 --- /dev/null +++ b/gn3/db/matrix.py @@ -0,0 +1,44 @@ +"""Methods for fetching data from the matrix stored in LMDB""" +from typing import Optional +from dataclasses import dataclass + +import struct +import json +import lmdb + +BLOB_HASH_DIGEST = 32 + + +@dataclass +class Matrix: + """Store sample data and any other relevant metadata""" + + data: list + metadata: dict + + +def get_current_matrix(db_path: str) -> Optional[Matrix]: + """Get the most recent matrix from DB_PATH. This is functionally + equivalent to get_nth_matrix(0, db_path)""" + env = lmdb.open(db_path) + with env.begin(write=False) as txn: + current_hash = txn.get(b"current") or b"" + matrix_hash = txn.get(current_hash + b":matrix") or b"" + row_pointers = txn.get(matrix_hash + b":row-pointers") + nrows = 0 + if matrix_hash: + (nrows,) = struct.unpack("