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Refactor bulk-generation of voucher codes into utility function

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This commit is contained in:
Raphael Michel
2021-08-23 12:50:02 +02:00
parent de977f4818
commit 276add9163
2 changed files with 54 additions and 52 deletions
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51
src/pretix/base/models/vouchers.py
View File

@@ -38,7 +38,7 @@ from decimal import ROUND_HALF_UP, Decimal
from django.conf import settings
from django.core.exceptions import ValidationError
from django.core.validators import MinLengthValidator
from django.db import models
from django.db import connection, models
from django.db.models import F, OuterRef, Q, Subquery, Sum
from django.db.models.functions import Coalesce
from django.utils.crypto import get_random_string
@@ -74,6 +74,55 @@ def generate_code(prefix=None):
return code
def generate_codes(organizer, num=1, prefix=None):
codes = set()
batch_size = 500
if 'postgres' in settings.DATABASES['default']['ENGINE']:
batch_size = 5_000
"""
We're trying to check if any of the requested codes already exists in the database. Generally, this is a
SELECT code FROM voucher WHERE code IN (…)
query. However, it turns out that this query get's rather slow if an organizer has lots of vouchers, even
with a organizer with just over 50_000 vouchers, we've seen that creating 20_000 new voucher codes took
just over 30 seconds. There's another way of doing this query on PostgreSQL, which is joining with a
temporary table
SELECT code FROM voucher INNER JOIN (VALUES …) vals(v) ON (code = v)
This is significantly faster, inserting 20_000 vouchers now takes 2-3s instead of 31s on the same dataset.
It's still slow, and removing the JOIN to the event table doesn't significantly speed it up. We might need
an entirely different approach at some point.
"""
while len(codes) < num:
new_codes = set()
for i in range(min(num - len(codes), batch_size)): # Work around SQLite's SQLITE_MAX_VARIABLE_NUMBER
new_codes.add(_generate_random_code(prefix=prefix))
if 'postgres' in settings.DATABASES['default']['ENGINE']:
with connection.cursor() as cursor:
args = list(new_codes) + [organizer.pk]
tmptable = "VALUES " + (", ".join(['(%s)'] * len(new_codes)))
cursor.execute(
f'SELECT code '
f'FROM "{Voucher._meta.db_table}" '
f'INNER JOIN ({tmptable}) vals(v) ON ("{Voucher._meta.db_table}"."code" = "v")'
f'INNER JOIN "{Event._meta.db_table}" ON ("{Voucher._meta.db_table}"."event_id" = "{Event._meta.db_table}"."id") '
f'WHERE "{Event._meta.db_table}"."organizer_id" = %s',
args
)
for row in cursor.fetchall():
new_codes.remove(row[0])
else:
new_codes -= set([v['code'] for v in Voucher.objects.filter(code__in=new_codes).values('code')])
codes |= new_codes
return list(codes)
class Voucher(LoggedModel):
"""
A Voucher can reserve ticket quota or allow special prices.

55
src/pretix/control/views/vouchers.py
View File

@@ -55,10 +55,8 @@ from django.views.generic import (
CreateView, DeleteView, ListView, TemplateView, UpdateView, View,
)
from pretix.base.models import (
CartPosition, Event, LogEntry, OrderPosition, Voucher,
)
from pretix.base.models.vouchers import _generate_random_code
from pretix.base.models import CartPosition, LogEntry, OrderPosition, Voucher
from pretix.base.models.vouchers import generate_codes
from pretix.base.services.locking import NoLockManager
from pretix.base.services.vouchers import vouchers_send
from pretix.base.views.tasks import AsyncFormView
@@ -458,60 +456,15 @@ class VoucherRNG(EventPermissionRequiredMixin, View):
permission = 'can_change_vouchers'
def get(self, request, *args, **kwargs):
codes = set()
try:
num = int(request.GET.get('num', '5'))
except ValueError: # NOQA
return HttpResponseBadRequest()
prefix = request.GET.get('prefix')
batch_size = 500
if 'postgres' in settings.DATABASES['default']['ENGINE']:
batch_size = 5_000
"""
We're trying to check if any of the requested codes already exists in the database. Generally, this is a
SELECT code FROM voucher WHERE code IN (…)
query. However, it turns out that this query get's rather slow if an organizer has lots of vouchers, even
with a organizer with just over 50_000 vouchers, we've seen that creating 20_000 new voucher codes took
just over 30 seconds. There's another way of doing this query on PostgreSQL, which is joining with a
temporary table
SELECT code FROM voucher INNER JOIN (VALUES …) vals(v) ON (code = v)
This is significantly faster, inserting 20_000 vouchers now takes 2-3s instead of 31s on the same dataset.
It's still slow, and removing the JOIN to the event table doesn't significantly speed it up. We might need
an entirely different approach at some point.
"""
while len(codes) < num:
new_codes = set()
for i in range(min(num - len(codes), batch_size)): # Work around SQLite's SQLITE_MAX_VARIABLE_NUMBER
new_codes.add(_generate_random_code(prefix=prefix))
if 'postgres' in settings.DATABASES['default']['ENGINE']:
with connection.cursor() as cursor:
args = list(new_codes) + [request.organizer.pk]
tmptable = "VALUES " + (", ".join(['(%s)'] * len(new_codes)))
cursor.execute(
f'SELECT code '
f'FROM "{Voucher._meta.db_table}" '
f'INNER JOIN ({tmptable}) vals(v) ON ("{Voucher._meta.db_table}"."code" = "v")'
f'INNER JOIN "{Event._meta.db_table}" ON ("{Voucher._meta.db_table}"."event_id" = "{Event._meta.db_table}"."id") '
f'WHERE "{Event._meta.db_table}"."organizer_id" = %s',
args
)
for row in cursor.fetchall():
new_codes.remove(row[0])
else:
new_codes -= set([v['code'] for v in Voucher.objects.filter(code__in=new_codes).values('code')])
codes |= new_codes
codes = generate_codes(request.organizer, num, prefix=prefix)
return JsonResponse({
'codes': list(codes)
'codes': codes
})
def get_success_url(self) -> str: