Re: Single thread creation queue?
Re: Single thread creation queue?
- Subject: Re: Single thread creation queue?
- From: Aaron Rosenzweig via Webobjects-dev <email@hidden>
- Date: Mon, 22 Nov 2021 11:19:01 -0500
Sounds like you are using Postgres?
You can use the syntax “not valid” when you create a constraint to stop the
bleeding immediately. It will then only check for new and modified records
allowing the bad rows to co-exist. When you get around to it, you can remove
the duplicates.
If it’s another database, they likely have something similar.
> On Nov 22, 2021, at 10:18 AM, Jesse Tayler <email@hidden> wrote:
>
> It’s not a compound key so much as just policy — it’s a handle for social
> service and so there should just be one row with that value and don’t need to
> tie into the key
>
> I guess I can create a unique index just for that one attribute and it would
> presumedly return an error upon save. I should re-write the EO to handle that
> error raise and respond by returning the existing object…
>
> I guess that is not hard to figure if that approach sounds sane.
>
> I do have dups and I’d guess the constraint will simply fail if the database
> has any dups in it.
>
> I guess writing a migration to handle / remove dups is not practical so I’d
> likely remove them by hand, then add the constraint in a migration update
> that would gently fail until there are no more dups…
>
>
>
>> On Nov 22, 2021, at 10:07 AM, Samuel Pelletier <email@hidden> wrote:
>>
>> Jesse,
>>
>> So your row have a primary key and some other unique identifier derived
>> other attributes.
>>
>> If the compound key is a combinaison of full attribute values, you cana a
>> compound unique key in the database. CREATE UNIQUE INDEX ON Table (col1,
>> col2, ..., coln)
>>
>> If it is from partial values, the most reliable way is to add a string
>> column with the computed key with it's unique constraint.
>>
>> If you already have duplicate, you can add a method in the migration to
>> resolve them before adding the constraint or do it manually...
>>
>> Regards,
>>
>> Samuel
>>
>>> Le 22 nov. 2021 à 09:27, Jesse Tayler <email@hidden> a écrit :
>>>
>>> It’s likely just a unique constraint perhaps.
>>>
>>> It’s not UIDs or primary keys it’s a unique row type based on a couple
>>> strings where there should be only one, and that one should last forever.
>>>
>>> There’s an API where calls can come in basically at the same time and
>>> instead of fetching first to see if the object exists, I should likely
>>> respond to an SQL error rejecting a new row and then fetch and return that
>>> existing object based on that error condition.
>>>
>>> I’d suppose the database is the best place for that policy, but I don’t
>>> think I’ve implemented constraints quite like that before so I’d need to
>>> write some sort of Migrations for it if it’s to be reliable in all those
>>> situations where it might encounter duplicate data…hmmm…
>>>
>>>
>>>
>>>
>>>> On Nov 22, 2021, at 8:59 AM, Samuel Pelletier <email@hidden> wrote:
>>>>
>>>> Hi Jesse,
>>>>
>>>> Your question may have multiple answers, can you describe the contexts and
>>>> duplicate sources you fear ?
>>>>
>>>> Is the primary key generated by the WO app or it is external (like a GUID)
>>>> ?
>>>>
>>>> Do you have a secondary identifier that should be unique ?
>>>>
>>>> Anyway, you should add constraint in to the database if uniqueness is
>>>> required (this apply to all frameworks in all language)
>>>>
>>>> If you use EOF primary key generation, you should not have problems with
>>>> duplicate keys. If you require high throughput, using UUID primary key or
>>>> implementing a custom generator will help by saving round trips to the
>>>> database server. If you insert in batch, it will be also faster than
>>>> individual inserts.
>>>>
>>>> Regards,
>>>>
>>>> Samuel
>>>>
>>>>> Le 22 nov. 2021 à 08:34, Jesse Tayler via Webobjects-dev
>>>>> <email@hidden> a écrit :
>>>>>
>>>>> I asked on slack but I figured I’d ping the list
>>>>>
>>>>> Who has a good way to ensure a serial EO creation queue when the system
>>>>> could be hit really fast and you must avoid duplicate entries?
>>>>>
>>>>> I’m a bit surprised I don’t recall EOF style solutions for such things
>>>>> and maybe the Amazon RDS database has a shared connection pattern the
>>>>> apps can use, I didn’t see anything so I figure this is application level
>>>>> stuff.
>>>>>
>>>>> Thoughts? Suggestions?
>>>>> _______________________________________________
>>>>> Do not post admin requests to the list. They will be ignored.
>>>>> Webobjects-dev mailing list (email@hidden)
>>>>> Help/Unsubscribe/Update your Subscription:
>>>>>
>>>>> This email sent to email@hidden
>>>>
>>>
>>
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden