[jira] [Resolved] (CALCITE-6403) Rule AGGREGATE_EXPAND_DISTINCT_AGGREGATES is unsound

["Mihai Budiu (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-6403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mihai Budiu resolved CALCITE-6403.
----------------------------------
    Fix Version/s: 1.42.0
       Resolution: Resolved

> 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
>             Fix For: 1.42.0
>
>
> 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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