DynamoDB limits the size of hash keys to 2048 bytes, sort keys

to 1024 bytes, and the entire item to 400 KB which therefore also
limits the size of one attribute. This test checks that we can
reach up to these limits, with binary keys and attributes.

The test does *not* check what happens once we exceed these
limits. In such a case, DynamoDB throws an error (I checked that
manually) but Alternator currently simply succeeds. If in the
future we decide to add artificial limits to Alternator as well,
we should add such tests as well.

Signed-off-by: Nadav Har'El <nyh@scylladb.com>

alternator-test/test_item.py

@@ -278,3 +278,28 @@ def test_bytes_sort_key(test_table_sb):
     val = random_string()
     test_table_sb.put_item(Item={'p': p, 'c': c, 'attribute': val})
     assert test_table_sb.get_item(Key={'p': p, 'c': c}, ConsistentRead=True)['Item'] == {'p': p, 'c': c, 'attribute': val}
+
+# Tests for using a large binary blob as hash key, sort key, or attribute.
+# DynamoDB strictly limits the size of the binary hash key to 2048 bytes,
+# and binary sort key to 1024 bytes, and refuses anything larger. The total
+# size of an item is limited to 400KB, which also limits the size of the
+# largest attributes. For more details on these limits, see
+# https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html
+# Alternator currently does *not* have these limitations, and can accept much
+# larger keys and attributes, but what we do in the following tests is to verify
+# that items up to DynamoDB's maximum sizes also work well in Alternator.
+def test_large_blob_hash_key(test_table_b):
+    b = random_bytes(2048)
+    test_table_b.put_item(Item={'p': b})
+    assert test_table_b.get_item(Key={'p': b}, ConsistentRead=True)['Item'] == {'p': b}
+def test_large_blob_sort_key(test_table_sb):
+    s = random_string()
+    b = random_bytes(1024)
+    test_table_sb.put_item(Item={'p': s, 'c': b})
+    assert test_table_sb.get_item(Key={'p': s, 'c': b}, ConsistentRead=True)['Item'] == {'p': s, 'c': b}
+def test_large_blob_attribute(test_table):
+    p = random_string()
+    c = random_string()
+    b = random_bytes(409500)  # a bit less than 400KB
+    test_table.put_item(Item={'p': p, 'c': c, 'attribute': b })
+    assert test_table.get_item(Key={'p': p, 'c': c}, ConsistentRead=True)['Item'] == {'p': p, 'c': c, 'attribute': b}