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READ ONLY transactions should prevent modifications to foreign data as well as local data, but postgres_fdw transactions declared as READ ONLY that reference foreign tables mapped to a remote view executing volatile functions would modify data on remote servers, as it would open remote transactions in READ WRITE mode. Similarly, DEFERRABLE transactions should not abort due to a serialization failure even when accessing foreign data, but postgres_fdw transactions declared as DEFERRABLE would abort due to that failure in a remote server, as it would open remote transactions in NOT DEFERRABLE mode. To fix, modify postgres_fdw to open remote transactions in the same access/deferrable modes as the local transaction. This commit also modifies it to open remote subtransactions in the same access mode as the local subtransaction. This commit changes the behavior of READ ONLY/DEFERRABLE transactions using postgres_fdw; in particular, it doesn't allow the READ ONLY transactions to modify data on remote servers anymore, so such transactions should be redeclared as READ WRITE or rewritten using other tools like dblink. The release notes should note this as an incompatibility. These issues exist since the introduction of postgres_fdw, but to avoid the incompatibility in the back branches, fix them in master only. Author: Etsuro Fujita <etsuro.fujita@gmail.com> Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Fujii Masao <masao.fujii@gmail.com> Discussion: https://postgr.es/m/CAPmGK16n_hcUUWuOdmeUS%2Bw4Q6dZvTEDHb%3DOP%3D5JBzo-M3QmpQ%40mail.gmail.com Discussion: https://postgr.es/m/E1uLe9X-000zsY-2g%40gemulon.postgresql.org |
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| eval_plan_qual.out | ||
| postgres_fdw.out | ||
| query_cancel.out | ||
| query_cancel_1.out | ||