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Fix bogus logic for reporting which hash partition conflicts.

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Commit efbfb6424 added logic for reporting exactly which existing
partition conflicts when complaining that a new hash partition's
modulus isn't compatible with the existing ones.  However, it
misunderstood the partitioning data structure, and would select
the wrong partition in some cases, or crash outright due to fetching
a bogus table OID in other cases.

Per bug #17076 from Alexander Lakhin.  Fix by Amit Langote;
some further work on the code comments by me.

Discussion: https://postgr.es/m/17076-89a16ae835d329b9@postgresql.org
This commit is contained in:
Tom Lane
2021-06-29 14:34:31 -04:00
parent dc227eb82e
commit dd2364ced9
3 changed files with 29 additions and 10 deletions
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26
src/backend/partitioning/partbounds.c
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@ -2838,12 +2838,15 @@ check_new_partition_bound(char *relname, Relation parent,
/*
* Check rule that every modulus must be a factor of the
* next larger modulus. For example, if you have a bunch
* next larger modulus. (For example, if you have a bunch
* of partitions that all have modulus 5, you can add a
* new partition with modulus 10 or a new partition with
* modulus 15, but you cannot add both a partition with
* modulus 10 and a partition with modulus 15, because 10
* is not a factor of 15.
* is not a factor of 15.) We need only check the next
* smaller and next larger existing moduli, relying on
* previous enforcement of this rule to be sure that the
* rest are in line.
*/
/*
@ -2870,15 +2873,16 @@ check_new_partition_bound(char *relname, Relation parent,
errmsg("every hash partition modulus must be a factor of the next larger modulus"),
errdetail("The new modulus %d is not a factor of %d, the modulus of existing partition \"%s\".",
spec->modulus, next_modulus,
get_rel_name(partdesc->oids[boundinfo->indexes[0]]))));
get_rel_name(partdesc->oids[0]))));
}
else
{
int prev_modulus;
/*
* We found the largest modulus less than or equal to
* ours.
* We found the largest (modulus, remainder) pair less
* than or equal to the new one. That modulus must be
* a divisor of, or equal to, the new modulus.
*/
prev_modulus = DatumGetInt32(boundinfo->datums[offset][0]);
@ -2889,13 +2893,19 @@ check_new_partition_bound(char *relname, Relation parent,
errdetail("The new modulus %d is not divisible by %d, the modulus of existing partition \"%s\".",
spec->modulus,
prev_modulus,
get_rel_name(partdesc->oids[boundinfo->indexes[offset]]))));
get_rel_name(partdesc->oids[offset]))));
if (offset + 1 < boundinfo->ndatums)
{
int next_modulus;
/* Look at the next higher modulus */
/*
* Look at the next higher (modulus, remainder)
* pair. That could have the same modulus and a
* larger remainder than the new pair, in which
* case we're good. If it has a larger modulus,
* the new modulus must divide that one.
*/
next_modulus = DatumGetInt32(boundinfo->datums[offset + 1][0]);
if (next_modulus % spec->modulus != 0)
@ -2904,7 +2914,7 @@ check_new_partition_bound(char *relname, Relation parent,
errmsg("every hash partition modulus must be a factor of the next larger modulus"),
errdetail("The new modulus %d is not a factor of %d, the modulus of existing partition \"%s\".",
spec->modulus, next_modulus,
get_rel_name(partdesc->oids[boundinfo->indexes[offset + 1]]))));
get_rel_name(partdesc->oids[offset + 1]))));
}
}