1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
|
#------------------------------------------------------------------------------
# Copyright (c) 2016, 2022, Oracle and/or its affiliates.
#
# This software is dual-licensed to you under the Universal Permissive License
# (UPL) 1.0 as shown at https://oss.oracle.com/licenses/upl and Apache License
# 2.0 as shown at http://www.apache.org/licenses/LICENSE-2.0. You may choose
# either license.
#
# If you elect to accept the software under the Apache License, Version 2.0,
# the following applies:
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#------------------------------------------------------------------------------
#------------------------------------------------------------------------------
# query_arraysize.py
#
# Demonstrates how to alter the array size and prefetch rows values in order to
# tune the performance of fetching data from the database. Increasing these
# values can reduce the number of network round trips and overhead required to
# fetch all of the rows from a large table. The value affect internal buffers
# and do not affect how, or when, rows are returned to your application.
#
# The best values need to be determined by tuning in your production
# environment.
#------------------------------------------------------------------------------
import time
import oracledb
import sample_env
# determine whether to use python-oracledb thin mode or thick mode
if not sample_env.get_is_thin():
oracledb.init_oracle_client(lib_dir=sample_env.get_oracle_client())
connection = oracledb.connect(user=sample_env.get_main_user(),
password=sample_env.get_main_password(),
dsn=sample_env.get_connect_string())
# Global values can be set to override the defaults used when a cursor is
# created
oracledb.defaults.prefetchrows = 200 # default is 2
oracledb.defaults.arraysize = 200 # default is 100
with connection.cursor() as cursor:
# Example 1
start = time.time()
cursor.execute('select * from bigtab')
res = cursor.fetchall()
elapsed = (time.time() - start)
print("Prefetchrows:", cursor.prefetchrows, "Arraysize:", cursor.arraysize)
print("Retrieved", len(res), "rows in", elapsed, "seconds")
# Example 2
start = time.time()
# values can be set per-cursor
cursor.prefetchrows = 1000
cursor.arraysize = 1000
cursor.execute('select * from bigtab')
res = cursor.fetchall()
# print(res) # uncomment to display the query results
elapsed = (time.time() - start)
print("Prefetchrows:", cursor.prefetchrows, "Arraysize:", cursor.arraysize)
print("Retrieved", len(res), "rows in", elapsed, "seconds")
|
