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Fix partial aggregation for variance(int4) and related aggregates.

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A typo in numeric_poly_combine caused bogus results for queries using
it, but of course would only manifest if parallel aggregation is
performed.  Reported by Rajkumar Raghuwanshi.

David Rowley did the diagnosis and the fix; I editorialized rather
heavily on his regression test additions.

Back-patch to v10 where the breakage was introduced (by 9cca11c91).

Discussion: https://postgr.es/m/CAKcux6nU4E2x8nkSBpLOT2DPvQ5LviJ3SGyAN6Sz7qDH4G4+Pw@mail.gmail.com
This commit is contained in:
Tom Lane 2018-06-21 16:18:34 -04:00
parent a4c95b0b80
commit b8a1d03020
3 changed files with 47 additions and 2 deletions
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4
src/backend/utils/adt/numeric.c
View File

@ -4054,8 +4054,8 @@ numeric_poly_combine(PG_FUNCTION_ARGS)
state1->sumX = state2->sumX;
state1->sumX2 = state2->sumX2;
#else
accum_sum_copy(&state2->sumX, &state1->sumX);
accum_sum_copy(&state2->sumX2, &state1->sumX2);
accum_sum_copy(&state1->sumX, &state2->sumX);
accum_sum_copy(&state1->sumX2, &state2->sumX2);
#endif
MemoryContextSwitchTo(old_context);

27
src/test/regress/expected/aggregates.out
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@ -2054,3 +2054,30 @@ SELECT balk(hundred) FROM tenk1;
(1 row)
ROLLBACK;
-- test coverage for aggregate combine/serial/deserial functions
BEGIN ISOLATION LEVEL REPEATABLE READ;
SET parallel_setup_cost = 0;
SET parallel_tuple_cost = 0;
SET min_parallel_table_scan_size = 0;
SET max_parallel_workers_per_gather = 4;
SET enable_indexonlyscan = off;
-- variance(int4) covers numeric_poly_combine
-- sum(int8) covers int8_avg_combine
EXPLAIN (COSTS OFF)
SELECT variance(unique1::int4), sum(unique1::int8) FROM tenk1;
QUERY PLAN
----------------------------------------------
Finalize Aggregate
-> Gather
Workers Planned: 4
-> Partial Aggregate
-> Parallel Seq Scan on tenk1
(5 rows)
SELECT variance(unique1::int4), sum(unique1::int8) FROM tenk1;
variance | sum
----------------------+----------
8334166.666666666667 | 49995000
(1 row)
ROLLBACK;

18
src/test/regress/sql/aggregates.sql
View File

@ -900,3 +900,21 @@ EXPLAIN (COSTS OFF) SELECT balk(hundred) FROM tenk1;
SELECT balk(hundred) FROM tenk1;
ROLLBACK;
-- test coverage for aggregate combine/serial/deserial functions
BEGIN ISOLATION LEVEL REPEATABLE READ;
SET parallel_setup_cost = 0;
SET parallel_tuple_cost = 0;
SET min_parallel_table_scan_size = 0;
SET max_parallel_workers_per_gather = 4;
SET enable_indexonlyscan = off;
-- variance(int4) covers numeric_poly_combine
-- sum(int8) covers int8_avg_combine
EXPLAIN (COSTS OFF)
SELECT variance(unique1::int4), sum(unique1::int8) FROM tenk1;
SELECT variance(unique1::int4), sum(unique1::int8) FROM tenk1;
ROLLBACK;