[英]python, sqlite, sqlcipher: very poor performance processing first request
我的python服務使用使用sqlcipher lib加密的sqlite數據庫。 處理第一個請求時出現性能問題。 數據庫非常小而簡單,請求很少。 但是在連接后處理第一個請求要花費大量的時間:0.4秒。
這是一個有效的測試腳本。 這也很簡單(大部分是准備工作和調試消息)。 它創建小型數據庫(帶加密和不帶加密),為它們填充一些數據,並測量SQL選擇的時間。
#!/usr/bin/env python
import time
import os.path
from pysqlcipher3 import dbapi2 as sqlcipher
class Timer:
"""Helper class for measuring elapsed time"""
def __init__(self):
self.start = None
def measure(self):
finish = time.perf_counter()
elapsed = None if self.start is None else finish - self.start
self.start = finish
return elapsed
def make_databse(db_name, key):
"""Create a small database with two tables: version and account.
Populate tables with some data.
"""
if os.path.exists(db_name):
print("Databse {} already exists".format(db_name))
return
db = sqlcipher.connect(db_name)
with db:
if key:
db.executescript('pragma key="{}";'.format(key))
db.execute("CREATE TABLE version(key INTEGER PRIMARY KEY ASC, ver);")
db.execute("INSERT INTO version(ver) VALUES ('aaa');")
db.execute("CREATE TABLE account(key INTEGER PRIMARY KEY ASC, name);")
cur = db.cursor()
for n_id in range(100):
cur.execute("INSERT INTO account(name) VALUES ('name {}');".format(n_id))
print("Test database created: {}, {}".format(
db_name,
"Key len={}".format(len(key)) if key else "Not encripted"))
def test_connect_and_reads(run_id, db_name, key, *tables_names):
"""Main test method: connect to db, make selects from specified
tables, measure timings
"""
print("{}: Start! Db: {}, {}".format(
run_id, db_name,
"Encripted, key len={}".format(len(key)) if key else "Not encripted"))
timer = Timer()
timer.measure()
db = sqlcipher.connect(db_name)
print("{}: Connect. Elapsed: {} sec".format(run_id, timer.measure()))
if key:
db.executescript('pragma key="{}";'.format(key))
print("{}: Provide Key. Elapsed: {} sec".format(run_id, timer.measure()))
else:
print("{}: Skip Provide Key. Elapsed: {} sec".format(run_id, timer.measure()))
for table_name in tables_names:
curs = db.execute("SELECT * FROM {};".format(table_name))
recs = [x for x in curs]
print("{}: Read {} records from table '{}'. Elapsed: {} sec".format(
run_id, len(recs), table_name, timer.measure()))
print("{}: done.".format(run_id))
print()
def main():
key = "DUMMYKEYDUMMYKEY"
make_databse("rabbits_enc.sqlite3", key) # prepare encrypted database
make_databse("rabbits.sqlite3", "") # prepare plaintext database
# test encrypted db
test_connect_and_reads(0, "rabbits_enc.sqlite3", key, 'version', 'account')
test_connect_and_reads(1, "rabbits_enc.sqlite3", key, 'account', 'version')
test_connect_and_reads(2, "rabbits_enc.sqlite3", key, 'account', 'account')
# test plaintext db
test_connect_and_reads(3, "rabbits.sqlite3", "", 'version', 'account')
test_connect_and_reads(4, "rabbits.sqlite3", "", 'account', 'version')
test_connect_and_reads(5, "rabbits.sqlite3", "", 'account', 'account')
if __name__ == '__main__':
main()
從該腳本的輸出中,我看到如果數據庫是加密的,則處理第一個SELECT會花費0.4秒。 如果數據庫是純文本,則沒有這樣的問題。
Databse rabbits_enc.sqlite3 already exists
Databse rabbits.sqlite3 already exists
0: Start! Db: rabbits_enc.sqlite3, Encripted, key len=16
0: Connect. Elapsed: 0.00016079703345894814 sec
0: Provide Key. Elapsed: 0.00215048500103876 sec
0: Read 1 records from table 'version'. Elapsed: 0.4296091449796222 sec
0: Read 100 records from table 'account'. Elapsed: 0.0009567929664626718 sec
0: done.
1: Start! Db: rabbits_enc.sqlite3, Encripted, key len=16
1: Connect. Elapsed: 7.332500535994768e-05 sec
1: Provide Key. Elapsed: 0.00037083501229062676 sec
1: Read 100 records from table 'account'. Elapsed: 0.4182819949928671 sec
1: Read 1 records from table 'version'. Elapsed: 0.0005165199982002378 sec
1: done.
2: Start! Db: rabbits_enc.sqlite3, Encripted, key len=16
2: Connect. Elapsed: 9.809300536289811e-05 sec
2: Provide Key. Elapsed: 0.0019192049512639642 sec
2: Read 100 records from table 'account'. Elapsed: 0.4121257350197993 sec
2: Read 100 records from table 'account'. Elapsed: 0.0008492250344716012 sec
2: done.
3: Start! Db: rabbits.sqlite3, Not encripted
3: Connect. Elapsed: 7.215503137558699e-05 sec
3: Skip Provide Key. Elapsed: 0.0002521659480407834 sec
3: Read 1 records from table 'version'. Elapsed: 0.0035479930229485035 sec
3: Read 100 records from table 'account'. Elapsed: 0.000983492995146662 sec
3: done.
4: Start! Db: rabbits.sqlite3, Not encripted
4: Connect. Elapsed: 7.175595965236425e-05 sec
4: Skip Provide Key. Elapsed: 0.004018213017843664 sec
4: Read 100 records from table 'account'. Elapsed: 0.0010135580087080598 sec
4: Read 1 records from table 'version'. Elapsed: 0.0014616100233979523 sec
4: done.
5: Start! Db: rabbits.sqlite3, Not encripted
5: Connect. Elapsed: 7.912697037681937e-05 sec
5: Skip Provide Key. Elapsed: 0.0003501430037431419 sec
5: Read 100 records from table 'account'. Elapsed: 0.0007411669939756393 sec
5: Read 100 records from table 'account'. Elapsed: 0.000722763012163341 sec
5: done.
我知道db加密會帶來一些開銷,但是在這種情況下它很大。 我相信我的配置中存在一些可以解決的問題。 有任何想法嗎?
默認情況下,SQLCipher使用PBKDF2(當前設置為64,000次迭代)來計算加密密鑰,此過程在設計上很慢。 通常,在將操作鎖定到文件的數據庫上鍵入密鑰之后,將在執行第一個SQL命令后派生密鑰。 我們在此處提供有關SQLCipher的常規性能指南。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.