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

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

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 7dc0df5263475aa26225caeb072712d0f771ea29..dce3095b3f3517891a2592f97bc393012a39199f 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -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);

diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 11674a077bc320c45b50aaabb9c9c65fa40f1db1..56d5fbb4fbaf7c0122556e388ae3154f0765d548 100644 (file)
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -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;

diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index 4ead553479c38080c9a2aa4b55f55be33fc79d60..651ca02536c765b070e6c4d87b415a9208dacc16 100644 (file)
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -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;