From: | Rob Nikander <rob(dot)nikander(at)gmail(dot)com> |
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To: | pgsql-general(at)postgresql(dot)org |
Subject: | Is the row version available in SQL? |
Date: | 2017-06-28 14:54:14 |
Message-ID: | 2558AA7C-1FF0-4BBC-8160-BF9DD41CCD0C@gmail.com |
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Lists: | pgsql-general |
Hi,
I'm reading about MVCC here: https://www.postgresql.org/docs/current/static/mvcc.html <https://www.postgresql.org/docs/current/static/mvcc.html>.
In some cases I can use these transaction isolation modes, but in other cases, I may want to manage the versions and concurrency manually. Is there a way to select the “version” of a row, or is that data hidden to ordinary SQL statements?
I’m thinking about a sequence of actions, which are logically a transaction, but start on one thread and complete later on another thread. I don’t think I can tie up a JDBC database connection for that long. I can add a `version bigint` column to my table, and the final update will look like:
update ... where id = ? and version = the_version_selected_earlier_in_a_different_thread
… and if that gets 0 rows, it can handle the conflict.
Rob
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