问题

I\'m following up in regards to a question that I asked earlier in which I sought to seek a conversion from a goofy/poorly written mysql query to postgresql. I believe I succeeded with that. Anyways, I\'m using data that was manually moved from a mysql database to a postgres database. I\'m using a query that looks like so:

  \"\"\"
  UPDATE krypdos_coderound cru

  set is_correct = case 
      when t.kv_values1 = t.kv_values2 then True 
      else False 
      end

  from 

  (select cr.id, 
    array_agg(
    case when kv1.code_round_id = cr.id 
    then kv1.option_id 
    else null end 
    ) as kv_values1,

    array_agg(
    case when kv2.code_round_id = cr_m.id 
    then kv2.option_id 
    else null end 
    ) as kv_values2

    from krypdos_coderound cr
     join krypdos_value kv1 on kv1.code_round_id = cr.id
     join krypdos_coderound cr_m 
       on cr_m.object_id=cr.object_id 
       and cr_m.content_type_id =cr.content_type_id 
     join krypdos_value kv2 on kv2.code_round_id = cr_m.id

   WHERE
     cr.is_master= False
     AND cr_m.is_master= True 
     AND cr.object_id=%s 
     AND cr.content_type_id=%s 

   GROUP BY cr.id  
  ) t

where t.id = cru.id
    \"\"\" % ( self.object_id, self.content_type.id)
  )

I have reason to believe that this works well. However, this has lead to a new issue. When trying to submit, I get an error from django that states:

IntegrityError at (some url): 
duplicate key value violates unique constraint \"krypdos_value_pkey\"

I\'ve looked at several of the responses posted on here and I haven\'t quite found the solution to my problem (although the related questions have made for some interesting reading). I see this in my logs, which is interesting because I never explicitly call insert- django must handle it:

   STATEMENT:  INSERT INTO \"krypdos_value\" (\"code_round_id\", \"variable_id\", \"option_id\", \"confidence\", \"freetext\")
   VALUES (1105935, 11, 55, NULL, E\'\') 
   RETURNING \"krypdos_value\".\"id\"

However, trying to run that results in the duplicate key error. The actual error is thrown in the code below.

 # Delete current coding         CodeRound.objects.filter(object_id=o.id,content_type=object_type,is_master=True).delete()
  code_round = CodeRound(object_id=o.id,content_type=object_type,coded_by=request.user,comments=request.POST.get(\'_comments\',None),is_master=True)
  code_round.save()
  for key in request.POST.keys():
    if key[0] != \'_\' or key != \'csrfmiddlewaretoken\':
      options = request.POST.getlist(key)
      for option in options:
        Value(code_round=code_round,variable_id=key,option_id=option,confidence=request.POST.get(\'_confidence_\'+key, None)).save()  #This is where it dies
  # Resave to set is_correct
  code_round.save()
  o.status = \'3\' 
  o.save(

I\'ve checked the sequences and such and they seem to be in order. At this point I\'m not sure what to do- I assume it\'s something on django\'s end but I\'m not sure. Any feedback would be much appreciated!

回答1:

This happend to me - it turns out you need to resync your primary key fields in Postgres. The key is the SQL statement:

SELECT setval('tablename_id_seq', (SELECT MAX(id) FROM tablename)+1)

回答2:

It appears to be a known difference of behaviour between the MySQL and SQLite (they update the next available primary key even when inserting an object with an explicit id) backends, and other backends like Postgres, Oracle, ... (they do not).

There is a ticket describing the same issue. Even though it was closed as invalid, it provides a hint that there is a Django management command to update the next available key.

To display the SQL updating all next ids for the application MyApp:

python manage.py sqlsequencereset MyApp

In order to have the statement executed, you can provide it as the input for the dbshell management command. For bash, you could type:

python manage.py sqlsequencereset MyApp | python manage.py dbshell

The advantage of the management commands is that abstracts away the underlying DB backend, so it will work even if later migrating to a different backend.

回答3:

I had an existing table in my "inventory" app and I wanted to add new records in Django admin and I got this error:

Duplicate key value violates unique constraint "inventory_part_pkey" DETAIL: Key (part_id)=(1) already exists.

As mentioned before, I run the code below to get the SQL command to reset the id-s:

python manage.py sqlsequencereset inventory

Piping the python manage.py sqlsequencereset inventory | python manage.py dbshell to the shell was not working

So I copied the generated raw SQL command
Then opened pgAdmin3 https://www.pgadmin.org for postgreSQL and opened my db
Clicked on the 6. icon (Execute arbitrary SQL queries)
Copied the statement what was generated

In my case the raw SQL command was:

BEGIN;
SELECT setval(pg_get_serial_sequence('"inventory_signup"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "inventory_signup";
SELECT setval(pg_get_serial_sequence('"inventory_supplier"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "inventory_supplier";
COMMIT;

Executed it with F5.

This fixed everything.

回答4:

In addition to zapphods answer:

In my case the indexing was indeed incorrect, since I had deleted all migrations, and the database probably 10-15 times when developing as I wasn't in the stage of migrating anything.

I was getting an IntegrityError on finished_product_template_finishedproduct_pkey

Reindex the table and restart runserver:

I was using pgadmin3 and for whichever index was incorrect and throwing duplicate key errors I navigated to the constraints and reindexed.

And then reindexed.

回答5:

The solution is that you need to resync your primary key fields as reported by "Hacking Life" who wrote an example SQL code but, as suggested by "Ad N" is better to run the Django command sqlsequencereset to get the exact SQL code that you can copy and past or run with another command.

As a further improvement to these answers I would suggest to you and other reader to dont' copy and paste the SQL code but, more safely, to execute the SQL query generated by sqlsequencereset from within your python code in this way (using the default database):

from django.core.management.color import no_style
from django.db import connection

from myapps.models import MyModel1, MyModel2


sequence_sql = connection.ops.sequence_reset_sql(no_style(), [MyModel1, MyModel2])
with connection.cursor() as cursor:
    for sql in sequence_sql:
        cursor.execute(sql)

I tested this code with Python3.6, Django 2.0 and PostgreSQL 10.

回答6:

If you have manually copied the databases, you may be running into the issue described here.

回答7:

I encountered this error because I was passing extra arguments to the save method in the wrong way.

For anybody who encounters this, try forcing UPDATE with:

instance_name.save(..., force_update=True)

If you get an error that you cannot pass force_insert and force_update at the same time, you're probably passing some custom arguments the wrong way, like I did.

回答8:

If you want to reset the PK on all of your tables, like me, you can use the PostgreSQL recommended way:

SELECT 'SELECT SETVAL(' ||
       quote_literal(quote_ident(PGT.schemaname) || '.' || quote_ident(S.relname)) ||
       ', COALESCE(MAX(' ||quote_ident(C.attname)|| '), 1) ) FROM ' ||
       quote_ident(PGT.schemaname)|| '.'||quote_ident(T.relname)|| ';'
FROM pg_class AS S,
     pg_depend AS D,
     pg_class AS T,
     pg_attribute AS C,
     pg_tables AS PGT
WHERE S.relkind = 'S'
    AND S.oid = D.objid
    AND D.refobjid = T.oid
    AND D.refobjid = C.attrelid
    AND D.refobjsubid = C.attnum
    AND T.relname = PGT.tablename
ORDER BY S.relname;

After running this query, you will need to execute the results of the query. I typically copy and paste into Notepad. Then I find and replace "SELECT with SELECT and ;" with ;. I copy and paste into pgAdmin III and run the query. It resets all of the tables in the database. More "professional" instructions are provided at the link above.

回答9:

I was getting the same error as the OP.

I had created some Django models, created a Postgres table based on the models, and added some rows to the Postgres table via Django Admin. Then I fiddled with some of the columns in the models (changing around ForeignKeys, etc.) but had forgotten to migrate the changes.

Running the migration commands solved my problem, which makes sense given the SQL answers above.

To see what changes would be applied, without actually applying them:
python manage.py makemigrations --dry-run --verbosity 3

If you're happy with those changes, then run:
python manage.py makemigrations

Then run:
python manage.py migrate

回答10:

I was getting a similar issue and nothing seemed to be working. If you need the data (ie cant exclude it when doing dump) make sure you have turned off (commented) any post_save receivers. I think the data would be imported but it would create the same model again because of these. Worked for me.

来源：https://stackoverflow.com/questions/11089850/integrityerror-duplicate-key-value-violates-unique-constraint-django-postgres

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django