Django-添加新数据时需要花费很长时间加载的模型页面

Question

I have a fairly simple model with a many to many relationship to another model. rom django.db import models

class MechanismReference(models.Model):
    reference = models.TextField(help_text=u'References to support the target information like PMID, KEGGID,etc.')
    reference_type = models.CharField(max_length=10, blank=True,
                                      help_text='Type of reference, the reference from KEGG, PIMD, PMC or other')
    mech_reference = models.ManyToManyField('Mechanism', blank=True, null=True, max_length=150)


    def sort_data(self):
        return self.mech_reference.order_by('pk')

    def __unicode__(self):
        return u'%s %s (%s)' % (
        self.reference_type, self.reference, ",".join(mechanism.molecule for mechanism in self.mech_reference.all()))

The Mechanism models is like this:

class Mechanism(models.Model):
    target = models.ForeignKey('TargetDictionary', blank=True, null=True,
                               help_text=u'Target associated with this mechanism of action (foreign key to target_dictionary table')
    molecule = models.ForeignKey('MoleculeDictionary', blank=False, null=False,
                                 help_text=u'Molregno for the drug (foreign key to molecule_dictionary table)')
    mechanism_type = models.ForeignKey('MechanismType', blank=True, null=True,
                                       help_text=u'Type of action of the drug on the target e.g., agonist/antagonist etc (foreign key to action_type table)')

    class Meta:
        ordering = ['molecule', ]
    def __unicode__(self):
        #
        if self.mechanism_type:
            return u'%s %s %s' % (self.molecule.molecule, self.target.name, self.mechanism_type.description)
        elif self.mechanism_type is None:
            return u'%s %s %s' % (self.molecule.molecule, self.target.name, self.mechanism_type.moa_qualifier)
        else:
            return u'%s %s %s' % (self.molecule.molecule, self.target.name, str(self.pk))

The mechanism model has got 2041 records. The reference page loads Okie when it executes select * from mechanism_reference. But whenever I add a new mechanism reference it takes so long sometime I get a server error(500). Obviously, the page would have all the records form Mechanism table pre-populated to enable adding a many to many relationship for a given reference. Can anyone point me why is it slow and is there a way to reduce the loading up time?

Again this is much slower in development or production server than my localserver.

I use xadmin and individual models doesn't have designated view. I have added my view and base_site.html.

View:

from django.shortcuts import render

from django.http import HttpResponse
from django.template import RequestContext, loader

def index(request):
    template = loader.get_template('idg/index.html')
    context = RequestContext(request, {})
    return HttpResponse(template.render(context))

Answer 1

You can try:

Mechanism.objects.all().prefetch_related('target', 'molecule')

This will prevent 2 extra queries for each Mechanism in the db.

See docs on prefetch_related for more info about how this works.