On 02/07/2016 10:24 PM, Michael Holzman wrote:
Greetings,
I am trying to understand the subject. I see in the documentation
(http://www.postgresql.org/docs/current/static/postgres-fdw.html) that
F.31.3. Transaction Management
During a query that references any remote tables on a foreign
server,postgres_fdwopens a transaction on the remote server if one is
not already open corresponding to the current local transaction. The
remote transaction is committed or aborted when the local transaction
commits or aborts. Savepoints are similarly managed by creating
corresponding remote savepoints.
The remote transaction usesSERIALIZABLEisolation level when the local
transaction hasSERIALIZABLEisolation level; otherwise it usesREPEATABLE
READisolation level. This choice ensures that if a query performs
multiple table scans on the remote server, it will get
snapshot-consistent results for all the scans. A consequence is that
successive queries within a single transaction will see the same data
from the remote server, even if concurrent updates are occurring on the
remote server due to other activities. That behavior would be expected
anyway if the local transaction usesSERIALIZABLEorREPEATABLE
READisolation level, but it might be surprising for aREAD COMMITTEDlocal
transaction. A futurePostgreSQLrelease might modify these rules.
Unfortunately, the Postgres Wiki
(https://wiki.postgresql.org/wiki/SQL/MED#No_transaction_management)
states quite the opposite:
No transaction management
FDW for PostgreSQL never emit transaction command such as BEGIN,
ROLLBACK and COMMIT. Thus, all SQL statements are executed in each
transaction when 'autocommit' was set to 'on'.
What is the correct state of the subject?
The documentation.
If you look a bottom of Wiki page you will find:
This page was last modified on 6 March 2012, at 11:11
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Regards,
Michael Holzman
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Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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