[Pgpool-general] EXPLAIN statement fails on 'kind mismatch'

[asaf at lingnu.com]

>> >> hello
>> >>
>> >> after 2 weeks pgpool-II (2.25) was working good,
>> >> I now have:
>> >> 'kind mismatch among backends. Possible last query was: "EXPLAIN
>> SELECT
>> >> *
>> >> FROM ycore.transfer_record WHERE
>> >> transfer_record_id>400" kind details are: 0[D] 1[C]'
>> >>
>> >> just when we wanted to move to production.
>> >>
>> >> all other things still work, also 'EXPLAIN' on other tables,
>> >> (also same query on this table worked until now)
>> >> I have full logs of pgpool + 2 postgres backends
>> >> how can I find out whats wrong ?
>> >
>> > Can you show me the outputs of EXPAIN which are executed directly on
>> > postgres backends? My bet is, there are dead tuples difference between
>> > backends which cause execution plan differences.
>> > --
>> > Tatsuo Ishii
>> > SRA OSS, Inc. Japan
>> >
>>
>> backend 0:
>>
>> explain select * from ycore.transfer_record where transfer_record_id >
>> 400;
>>                                        QUERY PLAN
>> -----------------------------------------------------------------------------------------
>>  Bitmap Heap Scan on transfer_record  (cost=4.60..20.16 rows=45
>> width=356)
>>    Recheck Cond: (transfer_record_id > 400)
>>    ->  Bitmap Index Scan on idx_tr_transfer_record_id  (cost=0.00..4.59
>> rows=45 width=0)
>>          Index Cond: (transfer_record_id > 400)
>> (4 rows)
>>
>>
>> backend 1:
>>
>> explain select * from ycore.transfer_record where transfer_record_id >
>> 400;
>>                             QUERY PLAN
>> -------------------------------------------------------------------
>>  Seq Scan on transfer_record  (cost=0.00..24.48 rows=49 width=331)
>>    Filter: (transfer_record_id > 400)
>> (2 rows)
>>
>>
>>
>> I can see there is a difference, but i don't know how to check what
>> caused
>> it, and how to avoid it next time.
>
> Please make sure that you have idx_tr_transfer_record_id index on
> backend 1. If you already have, please try vacuum analyze on the
> database directly on backend 1.
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
>

I have 'idx_tr_transfer_record_id' index on both backends,

i ran vacumm analyze as user postgres on backend 1:

vacuumdb --verbose --analyze --table transfer_record spy
INFO:  vacuuming "ycore.transfer_record"
INFO:  scanned index "transfer_record_pkey" to remove 14 row versions
DETAIL:  CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  scanned index "idx_tr_core_req_req_id" to remove 14 row versions
DETAIL:  CPU 0.00s/0.00u sec elapsed 0.53 sec.
INFO:  scanned index "idx_tr_transfer_record_id" to remove 14 row versions
DETAIL:  CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  "transfer_record": removed 14 row versions in 6 pages
DETAIL:  CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  index "transfer_record_pkey" now contains 445 row versions in 4 pages
DETAIL:  14 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  index "idx_tr_core_req_req_id" now contains 445 row versions in 4
pages
DETAIL:  14 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  index "idx_tr_transfer_record_id" now contains 445 row versions in
4 pages
DETAIL:  14 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  "transfer_record": found 9 removable, 446 nonremovable row versions
in 19 pages
DETAIL:  1 dead row versions cannot be removed yet.
There were 53 unused item pointers.
9 pages contain useful free space.
0 pages are entirely empty.
CPU 0.00s/0.00u sec elapsed 0.55 sec.
INFO:  vacuuming "pg_toast.pg_toast_17250"
INFO:  index "pg_toast_17250_index" now contains 0 row versions in 1 pages
DETAIL:  0 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  "pg_toast_17250": found 0 removable, 0 nonremovable row versions in
0 pages
DETAIL:  0 dead row versions cannot be removed yet.
There were 0 unused item pointers.
0 pages contain useful free space.
0 pages are entirely empty.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  analyzing "ycore.transfer_record"
INFO:  "transfer_record": scanned 19 of 19 pages, containing 445 live rows
and 1 dead rows; 445 rows in sample, 445 estimated total rows


after this, everything remains the same.
(EXPLAIN output, kind mismatch)