aboutsummaryrefslogtreecommitdiff
path: root/gn3
diff options
context:
space:
mode:
Diffstat (limited to 'gn3')
-rw-r--r--gn3/db/matrix.py44
1 files changed, 44 insertions, 0 deletions
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("<Q", txn.get(matrix_hash + b":nrows"))
+ data, metadata = None, None
+ if row_pointers:
+ return Matrix(
+ data=[
+ json.loads(txn.get(row_pointers[i: i + 32]).decode())
+ for i in range(0, nrows * 32, 32)
+ ],
+ metadata=json.loads(
+ txn.get(matrix_hash + b":metadata")
+ .rstrip(b"\x00")
+ .decode()
+ ),
+ )
+ return None