Re: postgres_fdw: Fix bug in checking of return value of PQsendQuery().

On Thu, 21 Jul 2022 at 22:22, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
> Hi,
>
> I found that fetch_more_data_begin() in postgres_fdw reports an error when PQsendQuery() returns the value less than 0 as follows though PQsendQuery() can return only 1 or 0. I think this is a bug. Attached is the patch that fixes this bug. This needs to be back-ported to v14 where async execution was supported in postgres_fdw.
>
> if (PQsendQuery(fsstate->conn, sql) < 0)
> pgfdw_report_error(ERROR, NULL, fsstate->conn, false, fsstate->query);
>
> Regards,

+1. However, I think check whether the result equals 0 or 1 might be better.
Anyway, the patch works correctly.

$ grep 'PQsendQuery(' -rn . --include '*.c'
./contrib/postgres_fdw/postgres_fdw.c:7073: if (PQsendQuery(fsstate->conn, sql) < 0)
./contrib/postgres_fdw/connection.c:647: if (!PQsendQuery(conn, sql))
./contrib/postgres_fdw/connection.c:782: if (!PQsendQuery(conn, query))
./contrib/postgres_fdw/connection.c:1347: if (!PQsendQuery(conn, query))
./contrib/postgres_fdw/connection.c:1575: if (PQsendQuery(entry->conn, "DEALLOCATE ALL"))
./contrib/dblink/dblink.c:720: retval = PQsendQuery(conn, sql);
./contrib/dblink/dblink.c:1146: if (!PQsendQuery(conn, sql))
./src/test/isolation/isolationtester.c:669: if (!PQsendQuery(conn, step->sql))
./src/test/modules/libpq_pipeline/libpq_pipeline.c:500: if (PQsendQuery(conn, "SELECT 1; SELECT 2") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:532: if (PQsendQuery(conn, "SELECT 1.0/g FROM generate_series(3, -1, -1) g") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1000: if (PQsendQuery(conn, "SELECT 1") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1046: if (PQsendQuery(conn, "SELECT 1") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1084: if (PQsendQuery(conn, "SELECT 1") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1094: if (PQsendQuery(conn, "SELECT 2") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1118: if (PQsendQuery(conn, "SELECT 1") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1132: if (PQsendQuery(conn, "SELECT 2") != 1)
./src/test/modules/libpq_pipeline/libpq_pipeline.c:1159: if (PQsendQuery(conn, "SELECT pg_catalog.pg_advisory_unlock(1,1)") != 1)
./src/bin/pg_basebackup/pg_basebackup.c:1921: if (PQsendQuery(conn, basebkp) == 0)
./src/bin/pg_amcheck/pg_amcheck.c:891: if (PQsendQuery(slot->connection, sql) == 0)
./src/bin/psql/common.c:1451: success = PQsendQuery(pset.db, query);
./src/bin/scripts/reindexdb.c:551: status = PQsendQuery(conn, sql.data) == 1;
./src/bin/scripts/vacuumdb.c:947: status = PQsendQuery(conn, sql) == 1;
./src/bin/pgbench/pgbench.c:3089: r = PQsendQuery(st->con, sql);
./src/bin/pgbench/pgbench.c:4012: if (!PQsendQuery(st->con, "ROLLBACK"))
./src/backend/replication/libpqwalreceiver/libpqwalreceiver.c:663: if (!PQsendQuery(streamConn, query))
./src/interfaces/libpq/fe-exec.c:1421:PQsendQuery(PGconn *conn, const char *query)
./src/interfaces/libpq/fe-exec.c:2319: if (!PQsendQuery(conn, query))

--
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.