[英]peewee.OperationalError: too many SQL variables on upsert of only 150 rows * 8 columns
使用下面的示例,在我的机器上,设置range(150)
导致错误,而range(100)
不会:
from peewee import *
database = SqliteDatabase(None)
class Base(Model):
class Meta:
database = database
colnames = ["A", "B", "C", "D", "E", "F", "G", "H"]
cols = {x: TextField() for x in colnames}
table = type('mytable', (Base,), cols)
database.init('test.db')
database.create_tables([table])
data = []
for x in range(150):
data.append({x: 1 for x in colnames})
with database.atomic() as txn:
table.insert_many(data).upsert().execute()
导致:
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/peewee.py", line 3213, in execute
cursor = self._execute()
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/peewee.py", line 2628, in _execute
return self.database.execute_sql(sql, params, self.require_commit)
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/peewee.py", line 3461, in execute_sql
self.commit()
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/peewee.py", line 3285, in __exit__
reraise(new_type, new_type(*exc_args), traceback)
File "/cluster/home/ifiddes/python2.7/lib/python2.7/site-packages/peewee.py", line 3454, in execute_sql
cursor.execute(sql, params or ())
peewee.OperationalError: too many SQL variables
这对我来说似乎很低落。 我正在尝试使用peewee
来替换现有的基于pandas
的SQL构造,因为pandas
缺乏对主键的支持。 只能在每个循环中插入~100条记录非常低,如果列数在某一天上升,则非常脆弱。
我怎样才能让这项工作变得更好? 可能吗?
经过一些调查后,问题似乎与sql查询可以拥有的最大参数数量有关 :SQLITE_MAX_VARIABLE_NUMBER。
为了能够进行大量批量插入,我首先估计SQLITE_MAX_VARIABLE_NUMBER,然后使用它在我想要插入的字典列表中创建块。
为了估计值,我使用此功能的灵感来自这个答案 :
def max_sql_variables():
"""Get the maximum number of arguments allowed in a query by the current
sqlite3 implementation. Based on `this question
`_
Returns
-------
int
inferred SQLITE_MAX_VARIABLE_NUMBER
"""
import sqlite3
db = sqlite3.connect(':memory:')
cur = db.cursor()
cur.execute('CREATE TABLE t (test)')
low, high = 0, 100000
while (high - 1) > low:
guess = (high + low) // 2
query = 'INSERT INTO t VALUES ' + ','.join(['(?)' for _ in
range(guess)])
args = [str(i) for i in range(guess)]
try:
cur.execute(query, args)
except sqlite3.OperationalError as e:
if "too many SQL variables" in str(e):
high = guess
else:
raise
else:
low = guess
cur.close()
db.close()
return low
SQLITE_MAX_VARIABLE_NUMBER = max_sql_variables()
然后我使用上面的变量来切片data
with database.atomic() as txn:
size = (SQLITE_MAX_VARIABLE_NUMBER // len(data[0])) -1
# remove one to avoid issue if peewee adds some variable
for i in range(0, len(data), size):
table.insert_many(data[i:i+size]).upsert().execute()
有关max_sql_variables
执行速度的max_sql_variables
。
在具有4核和4 Gb RAM的3年历史的Intel机器上运行OpenSUSE风滚草,SQLITE_MAX_VARIABLE_NUMBER设置为999,该功能运行时间不到100毫秒。 如果我设置high = 1000000
,则执行时间变为300ms的量级。
在具有8核和8Gb RAM的年轻英特尔机器上,运行Kubuntu,SQLITE_MAX_VARIABLE_NUMBER设置为250000,该功能在大约2.6秒内运行并返回99999.如果我设置high = 1000000
,则执行时间变为4.5秒的量级。
看这里, https://www.sqlite.org/limits.html#max_column似乎限制应该是2000:
SQLITE_MAX_COLUMN编译时参数用于设置上限:
- ......剪...
- INSERT语句中的值的数量
我猜你是否会以某种方式碰撞极限? 无论如何,只需输入您的输入或重新编译具有更高限制的SQLite。
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