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postgres_fdw: Fix "may be used uninitialized" warning in foreign_join_ok()

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Commit 0ee83dd4a9 detected the mixed foreign x function-RTE cases in one
if/else chain that only set a pair of bool flags, then acted on those flags in
a second chain.  fpinfo_o and fpinfo_i are each assigned in one chain and read
in the other, so proving them initialized requires correlating the flags with
the assignments.  gcc 13 with -Og does not manage that and reports fpinfo_i as
possibly uninitialized; clang's -Wconditional-uninitialized likewise reports
both variables.

The flags served no purpose beyond deferring the work, so merge the two chains
and read both fdw_private pointers up front, unconditionally.  A function rel
never has an fdw_private of its own, so the pointer is simply NULL until the
stub replaces it, and each branch now assigns and uses the two variables in one
place.

Reported-by: Karina Litskevich <litskevichkarina@gmail.com>
Reported-by: Marina Polyakova <m.polyakova@postgrespro.ru>
Reviewed-by: Marina Polyakova <m.polyakova@postgrespro.ru>
Discussion: https://postgr.es/m/CACiT8iamoL-%3D792e6JK2uCVvwDhfCg7DXHhvqN0P33jhGg2-8A%40mail.gmail.com
This commit is contained in:
Alexander Korotkov
2026-09-02 15:46:47 +03:00
parent 7d3247ccd1
commit 0fb258d1f2
1 changed files with 20 additions and 35 deletions
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55
contrib/postgres_fdw/postgres_fdw.c
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@@ -7045,8 +7045,6 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
PgFdwRelationInfo *fpinfo_i;
ListCell *lc;
List *joinclauses;
bool outer_is_function = false;
bool inner_is_function = false;
/*
* We support pushing down INNER, LEFT, RIGHT, FULL OUTER and SEMI joins.
@@ -7070,40 +7068,22 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
* function RTE can be absorbed into joins on multiple foreign servers
* (each call gets its own stub fpinfo and rechecks shippability for the
* specific server).
*
* A function rel has no fdw_private of its own, so when one side is a
* function RTE we replace its NULL fpinfo with a stub, and the rest of
* this function and the cost estimator can then treat both sides
* uniformly. We hand the stub to the joinrel's deparser via the same
* path the foreign side uses, but we never permanently attach it to the
* function rel's fdw_private (different joinrels may pair the same
* function RTE with different foreign servers).
*/
fpinfo = (PgFdwRelationInfo *) joinrel->fdw_private;
if (jointype == JOIN_INNER && innerrel->rtekind == RTE_FUNCTION &&
(fpinfo_o = (PgFdwRelationInfo *) outerrel->fdw_private) &&
fpinfo_o->pushdown_safe &&
function_rte_pushdown_ok(root, innerrel, outerrel))
{
inner_is_function = true;
}
else if (jointype == JOIN_INNER && outerrel->rtekind == RTE_FUNCTION &&
(fpinfo_i = (PgFdwRelationInfo *) innerrel->fdw_private) &&
fpinfo_i->pushdown_safe &&
function_rte_pushdown_ok(root, outerrel, innerrel))
{
outer_is_function = true;
}
else
{
fpinfo_o = (PgFdwRelationInfo *) outerrel->fdw_private;
fpinfo_i = (PgFdwRelationInfo *) innerrel->fdw_private;
if (!fpinfo_o || !fpinfo_o->pushdown_safe ||
!fpinfo_i || !fpinfo_i->pushdown_safe)
return false;
}
fpinfo_o = (PgFdwRelationInfo *) outerrel->fdw_private;
fpinfo_i = (PgFdwRelationInfo *) innerrel->fdw_private;
/*
* If one side is a function RTE, allocate a stub fpinfo so the rest of
* this function and the cost estimator can treat it uniformly. We hand
* the stub to the joinrel's deparser via the same path the foreign side
* uses, but we never permanently attach it to the function rel's
* fdw_private (different joinrels may pair the same function RTE with
* different foreign servers).
*/
if (inner_is_function)
if (jointype == JOIN_INNER && innerrel->rtekind == RTE_FUNCTION &&
fpinfo_o && fpinfo_o->pushdown_safe &&
function_rte_pushdown_ok(root, innerrel, outerrel))
{
fpinfo_i = init_func_stub_fpinfo(fpinfo_o, innerrel);
@@ -7118,15 +7098,20 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
&fpinfo_i->remote_conds, &fpinfo_i->local_conds);
fpinfo->inner_func_fpinfo = fpinfo_i;
}
else if (outer_is_function)
else if (jointype == JOIN_INNER && outerrel->rtekind == RTE_FUNCTION &&
fpinfo_i && fpinfo_i->pushdown_safe &&
function_rte_pushdown_ok(root, outerrel, innerrel))
{
fpinfo_o = init_func_stub_fpinfo(fpinfo_i, outerrel);
/* See the comment in the inner_is_function branch above. */
/* See the comment in the branch above. */
classifyConditions(root, outerrel, fpinfo_o, outerrel->baserestrictinfo,
&fpinfo_o->remote_conds, &fpinfo_o->local_conds);
fpinfo->outer_func_fpinfo = fpinfo_o;
}
else if (!fpinfo_o || !fpinfo_o->pushdown_safe ||
!fpinfo_i || !fpinfo_i->pushdown_safe)
return false;
/*
* If joining relations have local conditions, those conditions are