From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> |
Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Documenting when to retry on serialization failure |
Date: | 2022-03-24 14:56:22 |
Message-ID: | 2968200.1648133782@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> writes:
> OK, I see what you mean. There are 2 types of transaction, one that
> reads inside the transaction, one that decides what value to use some
> other way.
> So now we have 2 cases, both of which generate uniqueness violations,
> but only one of which might succeed if retried. The patch does cover
> this, I guess, by saying be careful, but I would be happier if we can
> also add
> "this is thought to occur only with multiple unique constraints and/or
> an exclusion constraints"
Um, what's that got to do with it? The example in
read-write-unique-4.spec involves only a single pkey constraint.
We could add something trying to explain that if the application inserts a
value into a constrained column based on data it read earlier, then any
resulting constraint violation might be effectively a serialization
failure.
regards, tom lane
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