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Commit68a13f2

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Don't believe MinMaxExpr is leakproof without checking.
MinMaxExpr invokes the btree comparison function for its input datatype,so it's only leakproof if that function is. Many such functions areindeed leakproof, but others are not, and we should not just assume thatthey are. Hence, adjust contain_leaked_vars to verify the leakproofnessof the referenced function explicitly.I didn't add a regression test because it would need to depend onsome particular comparison function being leaky, and that's a movingtarget, per discussion.This has been wrong all along, so back-patch to supported branches.Discussion:https://postgr.es/m/31042.1546194242@sss.pgh.pa.us
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‎src/backend/optimizer/util/clauses.c

Lines changed: 30 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1579,7 +1579,6 @@ contain_leaked_vars_walker(Node *node, void *context)
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caseT_CaseExpr:
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caseT_CaseTestExpr:
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caseT_RowExpr:
1582-
caseT_MinMaxExpr:
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caseT_SQLValueFunction:
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caseT_NullTest:
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caseT_BooleanTest:
@@ -1636,6 +1635,36 @@ contain_leaked_vars_walker(Node *node, void *context)
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}
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break;
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1638+
caseT_MinMaxExpr:
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{
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/*
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* MinMaxExpr is leakproof if the comparison function it calls
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* is leakproof.
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*/
1644+
MinMaxExpr*minmaxexpr= (MinMaxExpr*)node;
1645+
TypeCacheEntry*typentry;
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boolleakproof;
1647+
1648+
/* Look up the btree comparison function for the datatype */
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typentry=lookup_type_cache(minmaxexpr->minmaxtype,
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TYPECACHE_CMP_PROC);
1651+
if (OidIsValid(typentry->cmp_proc))
1652+
leakproof=get_func_leakproof(typentry->cmp_proc);
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else
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{
1655+
/*
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* The executor will throw an error, but here we just
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* treat the missing function as leaky.
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*/
1659+
leakproof= false;
1660+
}
1661+
1662+
if (!leakproof&&
1663+
contain_var_clause((Node*)minmaxexpr->args))
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return true;
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}
1666+
break;
1667+
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caseT_CurrentOfExpr:
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/*

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