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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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34
src/backend/optimizer/plan/createplan.c
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@ -1112,9 +1112,9 @@ create_join_plan(PlannerInfo *root, JoinPath *best_path)
/*
* mark_async_capable_plan
* Check whether a given Path node is async-capable, and if so, mark the
* Plan node created from it as such and return true, otherwise return
* false.
* Check whether the Plan node created from a Path node is async-capable,
* and if so, mark the Plan node as such and return true, otherwise
* return false.
*/
static bool
mark_async_capable_plan(Plan *plan, Path *path)
@ -1125,6 +1125,13 @@ mark_async_capable_plan(Plan *plan, Path *path)
{
SubqueryScan *scan_plan = (SubqueryScan *) plan;
/*
* If the generated plan node includes a gating Result node,
* we can't execute it asynchronously.
*/
if (IsA(plan, Result))
return false;
/*
* If a SubqueryScan node atop of an async-capable plan node
* is deletable, consider it as async-capable.
@ -1139,6 +1146,13 @@ mark_async_capable_plan(Plan *plan, Path *path)
{
FdwRoutine *fdwroutine = path->parent->fdwroutine;
/*
* If the generated plan node includes a gating Result node,
* we can't execute it asynchronously.
*/
if (IsA(plan, Result))
return false;
Assert(fdwroutine != NULL);
if (fdwroutine->IsForeignPathAsyncCapable != NULL &&
fdwroutine->IsForeignPathAsyncCapable((ForeignPath *) path))
@ -1148,11 +1162,17 @@ mark_async_capable_plan(Plan *plan, Path *path)
case T_ProjectionPath:
/*
* If the generated plan node doesn't include a Result node,
* consider it as async-capable if the subpath is async-capable.
* If the generated plan node includes a Result node for
* the projection, we can't execute it asynchronously.
*/
if (!IsA(plan, Result) &&
mark_async_capable_plan(plan,
if (IsA(plan, Result))
return false;
/*
* create_projection_plan() would have pulled up the subplan, so
* check the capability using the subpath.
*/
if (mark_async_capable_plan(plan,
((ProjectionPath *) path)->subpath))
return true;
return false;