Re: postgresql : could not serialize access due to read/write dependencies among transactions

Am 01/18/2017 um 05:54 AM schrieb Neslisah Demirci:
> Hi ,
>
>
> I have problem about this issue ;
>
>
> could not serialize access due to read/write dependencies among transactions

That's something you have to expect when using SERIALIZABLE isolation
level. Maybe re-read
https://www.postgresql.org/docs/current/static/transaction-iso.html#XACT-SERIALIZABLE

> A message app like whatsapp i decided to use isolation level
> serializable if i use other transaction levels many conversations
> started with same number (think about whatsapp web sidebar multipling
> with same number every message).

Are you not using a sequence for generating these IDs? As those are
counting independent of transaction visibility...
What you say sounds more like "SELECT max(conversation_id) + 1 AS
new_conversation_id FROM ..."

> I also add an index to my query and my query's execution plan don't use
> seq scan .
>
>
> How can i solve this issue ? Can i solve this on db orr on app ?

a) switch to a sequence for generating these IDs (you can go back to a
lower isolation level then). You may get holes in the IDs then (on
rolled back transactions), but I don't see how that would not be
acceptable for conversation IDs
b) deal with it in the app (probably not what you want, think roud-trip
time)

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