Re: SPI isolation changes

Seino Yuki <seinoyu@oss.nttdata.com> writes:
> I also thought that using SPI_start_transaction would be more readable
> than using SPI_commit/SPI_rollback to implicitly start a transaction.
> What do you think?

I think you're trying to get us to undo commit 2e517818f, which
is not going to happen.  See the threads that led up to that:

Discussion: https://postgr.es/m/3375ffd8-d71c-2565-e348-a597d6e739e3@enterprisedb.com
Discussion: https://postgr.es/m/17416-ed8fe5d7213d6c25@postgresql.org

It looks to me like you can just change the transaction property
settings immediately after SPI_start_transaction if you want to.
Compare this bit in SnapBuildExportSnapshot:

    StartTransactionCommand();

    /* There doesn't seem to a nice API to set these */
    XactIsoLevel = XACT_REPEATABLE_READ;
    XactReadOnly = true;

Also look at the implementation of SPI_commit_and_chain,
particularly RestoreTransactionCharacteristics.

            regards, tom lane