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Don't try to parallelize array_agg() on an anonymous record type.
This doesn't work because record_recv requires the typmod that identifies the specific record type (in our session) and array_agg_deserialize has no convenient way to get that information. The result is an "input of anonymous composite types is not implemented" error. We could probably make this work if we had to, but it does not seem worth the trouble, given that it took this long to get a field report. Just shut off parallelization, as though record_recv didn't exist. Oversight in commit 16fd03e. Back-patch to v16 where that came in. Reported-by: Kirill Zdornyy <kirill@dineserve.com> Diagnosed-by: Richard Guo <guofenglinux@gmail.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/atLI5Kce2ie1zcYjU0w_kjtVaxiYbYGTihrkLDmGZQnRDD4pnXukIATaABbnIj9pUnelC4ESvCXMm4HAyHg-v61XABaKpERj0A2IXzJZM7g=@dineserve.com Backpatch-through: 16
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+36
-4
lines changed

3 files changed

+36
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lines changed

‎src/backend/parser/parse_agg.c

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1958,7 +1958,7 @@ resolve_aggregate_transtype(Oid aggfuncid,
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/*
19601960
* agg_args_support_sendreceive
1961-
* Returns true if all non-byval of aggref's arg types have send and
1961+
* Returns true if all non-byval types of aggref's args have send and
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* receive functions.
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*/
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bool
@@ -1973,6 +1973,15 @@ agg_args_support_sendreceive(Aggref *aggref)
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TargetEntry *tle = (TargetEntry *) lfirst(lc);
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Oid type = exprType((Node *) tle->expr);
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1976+
/*
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* RECORD is a special case: it has typsend/typreceive functions, but
1978+
* record_recv only works if passed the correct typmod to identify the
1979+
* specific anonymous record type. array_agg_deserialize cannot do
1980+
* that, so we have to disclaim support for the case.
1981+
*/
1982+
if (type == RECORDOID)
1983+
return false;
1984+
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typeTuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type));
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if (!HeapTupleIsValid(typeTuple))
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elog(ERROR, "cache lookup failed for type %u", type);

‎src/test/regress/expected/aggregates.out

Lines changed: 19 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2033,8 +2033,8 @@ explain (costs off) select * from v_pagg_test order by y;
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-> Parallel Seq Scan on pagg_test
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(13 rows)
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2036-
set max_parallel_workers_per_gather = 0;
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-- Ensure results are the same without parallel aggregation.
2037+
set max_parallel_workers_per_gather = 0;
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select * from v_pagg_test order by y;
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y | tmin | tmax | tndistinct | bmin | bmax | bndistinct | amin | amax | andistinct | aamin | aamax | aandistinct
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---+------+------+------------+------+------+------------+------+------+------------+-------+-------+-------------
@@ -2050,6 +2050,24 @@ select * from v_pagg_test order by y;
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9 | 19 | 4999 | 250 | 1019 | 999 | 250 | 19 | 4999 | 250 | 19 | 4999 | 250
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(10 rows)
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2053+
-- Check that we don't fail on anonymous record types.
2054+
set max_parallel_workers_per_gather = 2;
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explain (costs off)
2056+
select array_dims(array_agg(s)) from (select * from pagg_test) s;
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QUERY PLAN
2058+
--------------------------------------------
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Aggregate
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-> Gather
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Workers Planned: 2
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-> Parallel Seq Scan on pagg_test
2063+
(4 rows)
2064+
2065+
select array_dims(array_agg(s)) from (select * from pagg_test) s;
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array_dims
2067+
------------
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[1:5000]
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(1 row)
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-- Clean up
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reset max_parallel_workers_per_gather;
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reset bytea_output;

‎src/test/regress/sql/aggregates.sql

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -805,11 +805,16 @@ select * from v_pagg_test order by y;
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-- Ensure parallel aggregation is actually being used.
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explain (costs off) select * from v_pagg_test order by y;
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808-
set max_parallel_workers_per_gather = 0;
809-
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-- Ensure results are the same without parallel aggregation.
809+
set max_parallel_workers_per_gather = 0;
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select * from v_pagg_test order by y;
812811

812+
-- Check that we don't fail on anonymous record types.
813+
set max_parallel_workers_per_gather = 2;
814+
explain (costs off)
815+
select array_dims(array_agg(s)) from (select * from pagg_test) s;
816+
select array_dims(array_agg(s)) from (select * from pagg_test) s;
817+
813818
-- Clean up
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reset max_parallel_workers_per_gather;
815820
reset bytea_output;

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