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https://issues.apache.org/jira/browse/CALCITE-4491?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Stamatis Zampetakis resolved CALCITE-4491.
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Resolution: Fixed
> 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
> Fix For: 1.27.0
>
> Time Spent: 40m
> 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!
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