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Make dblink interruptible, via new libpqsrv APIs.

This replaces dblink's blocking libpq calls, allowing cancellation and
allowing DROP DATABASE (of a database not involved in the query).  Apart
from explicit dblink_cancel_query() calls, dblink still doesn't cancel
the remote side.  The replacement for the blocking calls consists of
new, general-purpose query execution wrappers in the libpqsrv facility.
Out-of-tree extensions should adopt these.  Use them in postgres_fdw,
replacing a local implementation from which the libpqsrv implementation
derives.  This is a bug fix for dblink.  Code inspection identified the
bug at least thirteen years ago, but user complaints have not appeared.
Hence, no back-patch for now.

Discussion: https://postgr.es/m/20231122012945.74@rfd.leadboat.com
This commit is contained in:
Noah Misch
2024-01-08 11:39:56 -08:00
parent 0efc831847
commit d3c5f37dd5
8 changed files with 180 additions and 95 deletions

View File

@ -3760,7 +3760,7 @@ create_cursor(ForeignScanState *node)
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(conn, buf.data);
res = pgfdw_get_result(conn);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, fsstate->query);
PQclear(res);
@ -3810,7 +3810,7 @@ fetch_more_data(ForeignScanState *node)
* The query was already sent by an earlier call to
* fetch_more_data_begin. So now we just fetch the result.
*/
res = pgfdw_get_result(conn, fsstate->query);
res = pgfdw_get_result(conn);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, fsstate->query);
@ -4159,7 +4159,7 @@ execute_foreign_modify(EState *estate,
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
res = pgfdw_get_result(fmstate->conn);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
@ -4229,7 +4229,7 @@ prepare_foreign_modify(PgFdwModifyState *fmstate)
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
res = pgfdw_get_result(fmstate->conn);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
PQclear(res);
@ -4571,7 +4571,7 @@ execute_dml_stmt(ForeignScanState *node)
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
dmstate->result = pgfdw_get_result(dmstate->conn, dmstate->query);
dmstate->result = pgfdw_get_result(dmstate->conn);
if (PQresultStatus(dmstate->result) !=
(dmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, dmstate->result, dmstate->conn, true,