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Disable asynchronous execution if using gating Result nodes.

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mark_async_capable_plan(), which is called from create_append_plan() to
determine whether subplans are async-capable, failed to take into
account that the given subplan created from a given subpath might
include a gating Result node if the subpath is a SubqueryScanPath or
ForeignPath, causing a segmentation fault there when the subplan created
from a SubqueryScanPath includes the Result node, or causing
ExecAsyncRequest() to throw an error about an unrecognized node type
when the subplan created from a ForeignPath includes the Result node,
because in the latter case the Result node was unintentionally
considered as async-capable, but we don't currently support executing
Result nodes asynchronously.  Fix by modifying mark_async_capable_plan()
to disable asynchronous execution in such cases.  Also, adjust code in
the ProjectionPath case in mark_async_capable_plan(), for consistency
with other cases, and adjust/improve comments there.

is_async_capable_path() added in commit 27e1f1456, which was rewritten
to mark_async_capable_plan() in a later commit, has the same issue,
causing the error at execution mentioned above, so back-patch to v14
where the aforesaid commit went in.

Per report from Justin Pryzby.

Etsuro Fujita, reviewed by Zhihong Yu and Justin Pryzby.

Discussion: https://postgr.es/m/20220408124338.GK24419%40telsasoft.com
This commit is contained in:
Etsuro Fujita
2022-04-28 15:15:00 +09:00
parent 55b5686511
commit 5c854e7a2c
3 changed files with 106 additions and 7 deletions
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13
contrib/postgres_fdw/sql/postgres_fdw.sql
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@ -3410,6 +3410,19 @@ UNION ALL
SELECT * FROM result_tbl ORDER BY a;
DELETE FROM result_tbl;
-- Disable async execution if we use gating Result nodes for pseudoconstant
-- quals
EXPLAIN (VERBOSE, COSTS OFF)
SELECT * FROM async_pt WHERE CURRENT_USER = SESSION_USER;
EXPLAIN (VERBOSE, COSTS OFF)
(SELECT * FROM async_p1 WHERE CURRENT_USER = SESSION_USER)
UNION ALL
(SELECT * FROM async_p2 WHERE CURRENT_USER = SESSION_USER);
EXPLAIN (VERBOSE, COSTS OFF)
SELECT * FROM ((SELECT * FROM async_p1 WHERE b < 10) UNION ALL (SELECT * FROM async_p2 WHERE b < 10)) s WHERE CURRENT_USER = SESSION_USER;
-- Test that pending requests are processed properly
SET enable_mergejoin TO false;
SET enable_hashjoin TO false;