1#
2# micro_blob.py
3#
4# This source file is part of the FoundationDB open source project
5#
6# Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
7#
8# Licensed under the Apache License, Version 2.0 (the "License");
9# you may not use this file except in compliance with the License.
10# You may obtain a copy of the License at
11#
12#     http://www.apache.org/licenses/LICENSE-2.0
13#
14# Unless required by applicable law or agreed to in writing, software
15# distributed under the License is distributed on an "AS IS" BASIS,
16# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17# See the License for the specific language governing permissions and
18# limitations under the License.
19#
20
21import fdb
22fdb.api_version(300)
23db = fdb.open()
24
25
26@fdb.transactional
27def clear_subspace(tr, subspace):
28    tr.clear_range_startswith(subspace.key())
29
30
31CHUNK_LARGE = 5
32
33blob = fdb.Subspace(('B',))
34
35
36@fdb.transactional
37def write_blob(tr, data):
38    if not len(data):
39        return
40    num_chunks = (len(data) + CHUNK_LARGE - 1) / CHUNK_LARGE
41    chunk_size = (len(data) + num_chunks) / num_chunks
42    chunks = [(n, n + chunk_size) for n in range(0, len(data), chunk_size)]
43    for start, end in chunks:
44        tr[blob[start]] = data[start:end]
45
46
47@fdb.transactional
48def read_blob(tr):
49    value = ''
50    for k, v in tr[blob.range()]:
51        value += v
52    return value
53
54
55clear_subspace(db, blob)
56write_blob(db, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ')
57print read_blob(db)
58