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https://issues.apache.org/jira/browse/CALCITE-6403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18041751#comment-18041751
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Zhen Chen commented on CALCITE-6403:
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I ran the test on the main branch, and the results appear to be consistent with
PostgreSQL. I'm not sure if this issue has been fixed already, or if I might
have misunderstood something. If you have time, could you please verify this
again?
{code:java}
!use blank
create table T (col1 INT, col2 INT);
(0 rows modified)!update
SELECT COUNT (*), COUNT (DISTINCT COL1) FROM T WHERE false;
+--------+--------+
| EXPR$0 | EXPR$1 |
+--------+--------+
| 0 | 0 |
+--------+--------+
(1 row)!ok
EnumerableCalc(expr#0..1=[{inputs}], expr#2=[CAST($t0):BIGINT NOT NULL],
EXPR$0=[$t2], EXPR$1=[$t1])
EnumerableAggregate(group=[{}], EXPR$0_g0=[MIN($1) FILTER $3],
EXPR$1_g0=[COUNT($0) FILTER $2])
EnumerableValues(tuples=[[]])
!plan {code}
> Rule AGGREGATE_EXPAND_DISTINCT_AGGREGATES is unsound
> ----------------------------------------------------
>
> Key: CALCITE-6403
> URL: https://issues.apache.org/jira/browse/CALCITE-6403
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.37.0
> Reporter: Mihai Budiu
> Priority: Minor
>
> Here is a simple SQL program that operates on a collection with no input rows:
> {code:sql}
> SELECT COUNT(*), COUNT(DISTINCT COL1) FROM T WHERE false
> {code}
> The rewrite rule expands this into:
> {code}
> LogicalProject(EXPR$0=[CAST($0):BIGINT NOT NULL], EXPR$1=[$1]), id = 39
> LogicalAggregate(group=[{}], EXPR$0=[MIN($1) FILTER $3],
> EXPR$1=[COUNT($0) FILTER $2]), id = 37
> LogicalProject(COL1=[$0], EXPR$0=[$1], $g_0=[=($2, 0)], $g_1=[=($2,
> 1)]), id = 35
> LogicalAggregate(group=[{0}], groups=[[{0}, {}]], EXPR$0=[COUNT()],
> $g=[GROUPING($0)]), id = 30
> LogicalValues(tuples=[[]]), id = 22
> {code}
> Notice that there is an inner group-by aggregate that produces an empty set,
> and an outer aggregation that uses MIN. MIN for an empty collection is NULL,
> whereas the original query should have produced 0.
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