server/func/image_hash: added docstrings to functions

server/szurubooru/func/image_hash.py

@@ -25,10 +25,11 @@ SAMPLE_WORDS = 16
 MAX_WORDS = 63
 SIG_CHUNK_BITS = 32
 
-SIG_BASE = 2*N_LEVELS + 2
+SIG_NUMS = 8 * N * N
+SIG_BASE = 2 * N_LEVELS + 2
 SIG_CHUNK_WIDTH = int(SIG_CHUNK_BITS / math.log2(SIG_BASE))
-SIG_CHUNK_NUMS = 8*N*N / SIG_CHUNK_WIDTH
+SIG_CHUNK_NUMS = SIG_NUMS / SIG_CHUNK_WIDTH
-assert 8*N*N % SIG_CHUNK_WIDTH == 0
+assert SIG_NUMS % SIG_CHUNK_WIDTH == 0
 
 Window = Tuple[Tuple[float, float], Tuple[float, float]]
 NpMatrix = np.ndarray
@@ -229,6 +230,18 @@ def normalized_distance(
 
 
 def pack_signature(signature: NpMatrix) -> bytes:
+    '''
+    Serializes the signature vector for efficient storage in a database.
+
+    Shifts the range of the signature vector from [-N_LEVELS,+N_LEVELS]
+    to [0, base]
+
+    The vector can then be broken up into chunks, with each chunk
+    consisting of SIG_CHUNK_WIDTH digits of radix `base`.
+
+    This is then converted into a more packed array consisting of
+    uint32 elements (for SIG_CHUNK_BITS = 32).
+    '''
     base = 2 * N_LEVELS + 1
     coding_vector = np.flipud(SIG_BASE**np.arange(SIG_CHUNK_WIDTH))
     return np.array([
@@ -238,6 +251,11 @@ def pack_signature(signature: NpMatrix) -> bytes:
 
 
 def unpack_signature(packed: bytes) -> NpMatrix:
+    '''
+    Deserializes the signature vector once recieved from the database.
+
+    Functions as an inverse transformation of pack_signature()
+    '''
     base = 2 * N_LEVELS + 1
     return np.ravel(np.array([
         [

server/szurubooru/func/posts.py

@@ -479,13 +479,10 @@ def test_sound(post: model.Post, content: bytes) -> None:
 
 
 def purge_post_signature(post: model.Post) -> None:
-    old_signature = (
+    (db.session
-        db.session
         .query(model.PostSignature)
         .filter(model.PostSignature.post_id == post.post_id)
-        .one_or_none())
+        .delete())
-    if old_signature:
-        db.session.delete(old_signature)
 
 
 def generate_post_signature(post: model.Post, content: bytes) -> None:
@@ -788,24 +785,25 @@ def merge_posts(
             .values(child_id=target_post_id))
         db.session.execute(update_stmt)
 
-    def transfer_flags(source_post_id: int, target_post_id: int) -> None:
-        target = get_post_by_id(target_post_id)
-        source = get_post_by_id(source_post_id)
-        target.flags = source.flags
-
     merge_tags(source_post.post_id, target_post.post_id)
     merge_comments(source_post.post_id, target_post.post_id)
     merge_scores(source_post.post_id, target_post.post_id)
     merge_favorites(source_post.post_id, target_post.post_id)
     merge_relations(source_post.post_id, target_post.post_id)
 
+    def transfer_flags(source_post_id: int, target_post_id: int) -> None:
+        target = get_post_by_id(target_post_id)
+        source = get_post_by_id(source_post_id)
+        target.flags = source.flags
+        db.session.flush()
+
     content = None
     if replace_content:
         content = files.get(get_post_content_path(source_post))
         transfer_flags(source_post.post_id, target_post.post_id)
-        purge_post_signature(source_post)
-        purge_post_signature(target_post)
 
+    # fixes unknown issue with SA's cascade deletions
+    purge_post_signature(source_post)
     delete(source_post)
     db.session.flush()
 
@@ -826,6 +824,14 @@ def search_by_image(image_content: bytes) -> List[Tuple[float, model.Post]]:
     query_signature = image_hash.generate_signature(image_content)
     query_words = image_hash.generate_words(query_signature)
 
+    '''
+    The unnest function is used here to expand one row containing the 'words'
+    array into multiple rows each containing a singular word.
+
+    Documentation of the unnest function can be found here:
+    https://www.postgresql.org/docs/9.2/functions-array.html
+    '''
+
     dbquery = '''
     SELECT s.post_id, s.signature, count(a.query) AS score
     FROM post_signature AS s, unnest(s.words, :q) AS a(word, query)

server/szurubooru/model/post.py

@@ -207,7 +207,7 @@ class Post(Base):
     signature = sa.orm.relationship(
         'PostSignature',
         uselist=False,
-        cascade='all, delete-orphan',
+        cascade='all, delete, delete-orphan',
         lazy='joined')
     relations = sa.orm.relationship(
         'Post',