Re: Fix race condition in pg_get_publication_tables with concurrent DROP TABLE

> On May 1, 2026, at 09:30, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote:
>
> Hi,
>
> On Wed, Apr 29, 2026 at 8:41 PM Chao Li <li.evan.chao@gmail.com> wrote:
>>
>>>
<v5-0001-PG16-Fix-pg_get_publication_tables-race-with-conc.txt><v5-0001-Fix-pg_get_publication_tables-race-with-concurren.patch><v5-0001-PG18-Fix-pg_get_publication_tables-race-with-conc.txt><v5-0001-PG17-Fix-pg_get_publication_tables-race-with-conc.txt>
>>
>> I am afraid this is only a partial fix.
>
> Thanks for reviewing it. Please find my responses below.
>
>> ```
>> @@ -1599,12 +1621,18 @@ pg_get_publication_tables(FunctionCallInfo fcinfo, ArrayType *pubnames,
>>                /* Show all columns when the column list is not specified. */
>>                if (nulls[2])
>>                {
>> -                       Relation        rel = table_open(relid, AccessShareLock);
>> +                       Relation        rel = try_table_open(relid, AccessShareLock);
>>                        int                     nattnums = 0;
>>                        int16      *attnums;
>> -                       TupleDesc       desc = RelationGetDescr(rel);
>> +                       TupleDesc       desc;
>>                        int                     i;
>>
>> +                       /* Skip if the relation has been concurrently dropped. */
>> +                       if (rel == NULL)
>> +                               continue;
>> ```
>>
>> This change uses try_table_open() to detect whether a table has been dropped, but try_table_open() is only called
whenthe column list is not specified. If a table is included in the publication with an explicit column list, then even
ifit is dropped concurrently, it may still be returned by pg_get_publication_tables(). 
>
> Right. The try_table_open() is only needed there because that's the
> only code path that actually opens the relation (to enumerate its
> columns). The column list path reads from the pg_publication_rel
> catalog - it never calls table_open(), so it cannot hit the ERROR.
>
>> So this patch removes the “could not open relation with OID” error, but it does not fully ensure the accuracy of the
returnedtable list. 
>
> IMO, no function returning table OIDs can guarantee they remain valid
> - a drop can happen right after we return the OID, and accuracy is in
> the caller's hands. All the callers of pg_get_publication_tables()
> already handle this by JOINing with pg_class.
>

Fair.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/