[jira] [Assigned] (CALCITE-4491) Aggregation of window function produces invalid SQL for PostgreSQL

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-4491?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde reassigned CALCITE-4491:
------------------------------------

    Assignee: Julian Hyde

> Aggregation of window function produces invalid SQL for PostgreSQL
> ------------------------------------------------------------------
>
>                 Key: CALCITE-4491
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4491
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.26.0
>            Reporter: Dominik Labuda
>            Assignee: Julian Hyde
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> h2. Issue
> We tested the following behavior against PostgreSQL database, however more of the supported dialects may be affected.
> When aggregating the results of a window function an invalid SQL is generated. I was able to replicate the behavior in tests with:
> {code:java}
> @Test void testAggregatingWindowFunction() {
>     final RelBuilder builder = relBuilder();
>     final RelNode root = builder
>         .scan("EMP")
>         .project(
>             builder.alias(
>                 builder.getRexBuilder().makeOver(
>                     builder.getTypeFactory().createSqlType(SqlTypeName.INTEGER),
>                     SqlStdOperatorTable.RANK,
>                     new ArrayList<>(),
>                     new ArrayList<>(),
>                     ImmutableList.of(new RexFieldCollation(builder.field("SAL"), ImmutableSet.of())),
>                     RexWindowBounds.UNBOUNDED_PRECEDING,
>                     RexWindowBounds.UNBOUNDED_FOLLOWING,
>                     true,
>                     true,
>                     false,
>                     false,
>                     false
>                 ),
>                 "rank"
>             )
>         )
>         .as("tmp")
>         .aggregate(
>             builder.groupKey(),
>             builder.count(
>                 true,
>                 "cnt",
>                 builder.field("tmp", "rank")
>             )
>         )
>         .build();
>     final String expectedSql = "SELECT COUNT(DISTINCT \"rank\") AS \"cnt\"\n" +
>         "FROM (SELECT RANK() OVER (ORDER BY \"SAL\") AS \"rank\"\n" +
>         "FROM \"scott\".\"EMP\") AS \"t\"";
>     assertThat(
>         toSql(root, PostgresqlSqlDialect.DEFAULT),
>         isLinux(expectedSql)
>     );
>   }
> {code}
> The code above fails, since it produces this SQL instead of the expected one, which cannot be executed on PGSQL:
> {noformat}
> SELECT COUNT(DISTINCT RANK() OVER (ORDER BY "SAL")) AS "cnt"
> FROM "scott"."EMP"
> {noformat}
> In that case I am getting these kinds of errors from DB:
> {noformat}
> ERROR: aggregate function calls cannot contain window function calls
> {noformat}
> h2. Suggested solution
> Since _SqlDialect_ already contains support for determining whether the databases support nested aggregations via _public boolean supportsNestedAggregations()_ we could either add another method like _public boolean supportsNestedWindows()_ maybe _supportNestedWindowsInAggregation()_ to be more verbose. Or we could reuse the existing method for the window purposes (which seems non-transparent). Then we will be able to handle the behavior in _SqlImplementor.needNewSubQuery()_ similarly as it already does with the aggregations.
> Please let me know if you agree and I will be more than happy to provide you with PR to review, thanks!



--
This message was sent by Atlassian Jira
(v8.3.4#803005)