Jan Snelders <j...@snelders.net> wrote: > I wrote small java program which performs some selects in one > transaction (and thread) and one delete in another transaction and > thread on the same table holding one record initially. > The DELETE transaction commits. > The program now selects and > prints the records from the SELECT transaction. (0 records > printed, we expected one record since we are still within the > SELECT transaction which started while this record was still > available) You are probably running at the READ COMMITTED transaction isolation level. The behavior you describe is allowed at that isolation level, both by the standard and by PostgreSQL. You seem to be expecting that the default transaction isolation level will be SERIALIZABLE (which is not altogether unreasonable, since that is what the standard requires); but PostgreSQL has a default configuration of defaulting to the READ COMMITTED level. You can edit your postgresql.conf file to specify default_transaction_isolation = 'serializable' to get standard conforming behavior. Note that there are still some corner cases where you don't get full ACID behavior at the SERIALIZABLE level in PostgreSQL version 9.0; this has been enhanced to fully compliant behavior in the upcoming 9.1 release. For 9.0 behavior, see: http://www.postgresql.org/docs/9.0/static/transaction-iso.html For behavior in the soon-to-be-release 9.1 version, see: http://www.postgresql.org/docs/9.1/static/transaction-iso.html -Kevin
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