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Test, don't just Assert, that mergejoin's inputs are in order.

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There are two Asserts in nodeMergejoin.c that are reachable if
the input data is not in the expected order.  This seems way too
fragile.  Alexander Lakhin reported a case where the assertions
could be triggered with misconfigured foreign-table partitions,
and bitter experience with unstable operating system collation
definitions suggests another easy route to hitting them.  Neither
Assert is in a place where we can't afford one more test-and-branch,
so replace 'em with plain test-and-elog logic.

Per bug #17395.  While the reported symptom is relatively recent,
collation changes could happen anytime, so back-patch to all
supported branches.

Discussion: https://postgr.es/m/17395-8c326292078d1a57@postgresql.org
This commit is contained in:
Tom Lane 2022-02-05 11:59:29 -05:00
parent b31e3f5613
commit 5e26aa641e
1 changed files with 6 additions and 6 deletions
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12
src/backend/executor/nodeMergejoin.c
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@ -893,11 +893,10 @@ ExecMergeJoin(PlanState *pstate)
if (compareResult == 0)
node->mj_JoinState = EXEC_MJ_JOINTUPLES;
else
{
Assert(compareResult < 0);
else if (compareResult < 0)
node->mj_JoinState = EXEC_MJ_NEXTOUTER;
}
else /* compareResult > 0 should not happen */
elog(ERROR, "mergejoin input data is out of order");
break;
case MJEVAL_NONMATCHABLE:
@ -1087,7 +1086,7 @@ ExecMergeJoin(PlanState *pstate)
node->mj_JoinState = EXEC_MJ_JOINTUPLES;
}
else
else if (compareResult > 0)
{
/* ----------------
* if the new outer tuple didn't match the marked inner
@ -1106,7 +1105,6 @@ ExecMergeJoin(PlanState *pstate)
* no more inners, no more matches are possible.
* ----------------
*/
Assert(compareResult > 0);
innerTupleSlot = node->mj_InnerTupleSlot;
/* reload comparison data for current inner */
@ -1140,6 +1138,8 @@ ExecMergeJoin(PlanState *pstate)
return NULL;
}
}
else /* compareResult < 0 should not happen */
elog(ERROR, "mergejoin input data is out of order");
break;
/*----------------------------------------------------------