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pg_plan_advice: Avoid a crash under GEQO.

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The previous code could allocate pgpa_sj_unique_rel objects in a context
that had too short a lifespan. Fix by allocating them (and any
associated List-related allocations) in the same context as the
pgpa_planner_state to which they are attached. We also need to copy
uniquerel->relids, because the associated RelOptInfo may also be
allocated within a short-lived context.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: http://postgr.es/m/a6e6d603-e847-44dc-acd5-879fb4570062@gmail.com
This commit is contained in:
Robert Haas 2026-03-17 14:25:43 -04:00
parent e0e4c132ef
commit 01b02c0eca
1 changed files with 15 additions and 2 deletions
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17
contrib/pg_plan_advice/pgpa_planner.c
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@ -90,6 +90,7 @@ typedef enum pgpa_jo_outcome
typedef struct pgpa_planner_state
{
MemoryContext mcxt;
bool generate_advice_feedback;
bool generate_advice_string;
pgpa_trove *trove;
@ -324,10 +325,18 @@ pgpa_planner_setup(PlannerGlobal *glob, Query *parse, const char *query_string,
* some purpose. That could be (1) recording that we will need to generate
* an advice string, (2) storing a trove of supplied advice, or (3)
* facilitating debugging cross-checks when asserts are enabled.
*
* Currently, the active memory context should be one that will last for
* the entire duration of query planning, but if GEQO is in use, it's
* possible that some of our callbacks may be invoked later with
* CurrentMemoryContext set to some shorter-lived context. So, record the
* context that should be used for allocations that need to live as long
* as the pgpa_planner_state itself.
*/
if (needs_pps)
{
pps = palloc0_object(pgpa_planner_state);
pps->mcxt = CurrentMemoryContext;
pps->generate_advice_feedback = generate_advice_feedback;
pps->generate_advice_string = generate_advice_string;
pps->trove = trove;
@ -616,11 +625,15 @@ pgpa_join_path_setup(PlannerInfo *root, RelOptInfo *joinrel,
/* If not a duplicate, append to the list. */
if (!found)
{
pgpa_sj_unique_rel *ur = palloc_object(pgpa_sj_unique_rel);
pgpa_sj_unique_rel *ur;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(pps->mcxt);
ur = palloc_object(pgpa_sj_unique_rel);
ur->plan_name = root->plan_name;
ur->relids = uniquerel->relids;
ur->relids = bms_copy(uniquerel->relids);
pps->sj_unique_rels = lappend(pps->sj_unique_rels, ur);
MemoryContextSwitchTo(oldcontext);
}
}
}