From 700e8fe6d414ebaf9820fef364097d9b83cae7fd Mon Sep 17 00:00:00 2001 From: Etsuro Fujita Date: Fri, 21 Jan 2022 17:45:02 +0900 Subject: [PATCH] postgres_fdw: Fix subabort cleanup of connections used in asynchronous execution. Commit 27e1f1456 resets the per-connection states of connections used to scan foreign tables asynchronously during abort cleanup at main transaction end, but it failed to do so during subabort cleanup at subtransaction end, leading to a segmentation fault when re-executing an asynchronous-foreign-table-scan query in a transaction that was cancelled in a subtransaction of it. Fix by modifying pgfdw_abort_cleanup() to reset the per-connection state of a given connection also when called for subabort cleanup. Also, modify that function to do the reset in both the abort-cleanup and subabort-cleanup cases if necessary, to save cycles, and improve a comment on it a little bit. Back-patch to v14 where the aforesaid commit came in. Reviewed by Alexander Pyhalov Discussion: https://postgr.es/m/CAPmGK14cCV-JA7kNsyt2EUTKvZ4xkr2LNRthi1U1C3cqfGppAw@mail.gmail.com --- contrib/postgres_fdw/connection.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c index 1c7c76d1d4..35284419c9 100644 --- a/contrib/postgres_fdw/connection.c +++ b/contrib/postgres_fdw/connection.c @@ -977,8 +977,17 @@ pgfdw_xact_callback(XactEvent event, void *arg) { entry->have_prep_stmt = false; entry->have_error = false; - /* Also reset per-connection state */ - memset(&entry->state, 0, sizeof(entry->state)); + + /* + * If pendingAreq of the per-connection state is not + * NULL, it means that an asynchronous fetch begun by + * fetch_more_data_begin() was not done successfully + * and thus the per-connection state was not reset in + * fetch_more_data(); in that case reset the + * per-connection state here. + */ + if (entry->state.pendingAreq) + memset(&entry->state, 0, sizeof(entry->state)); } /* Disarm changing_xact_state if it all worked. */ @@ -1109,6 +1118,19 @@ pgfdw_subxact_callback(SubXactEvent event, SubTransactionId mySubid, curlevel, curlevel); if (!pgfdw_exec_cleanup_query(entry->conn, sql, false)) abort_cleanup_failure = true; + else + { + /* + * If pendingAreq of the per-connection state is not NULL, + * it means that an asynchronous fetch begun by + * fetch_more_data_begin() was not done successfully and + * thus the per-connection state was not reset in + * fetch_more_data(); in that case reset the + * per-connection state here. + */ + if (entry->state.pendingAreq) + memset(&entry->state, 0, sizeof(entry->state)); + } } /* Disarm changing_xact_state if it all worked. */