[jira] [Commented] (CALCITE-5284) JDBC rules create inefficient plan

["Ulrich Kramer (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-5284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17617086#comment-17617086 ] 

Ulrich Kramer commented on CALCITE-5284:
----------------------------------------

Is there someone who could answer [~libenchao] question? I would also be interested in this.

> JDBC rules create inefficient plan
> ----------------------------------
>
>                 Key: CALCITE-5284
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5284
>             Project: Calcite
>          Issue Type: Bug
>         Environment: Calcite 1.31.1. on Mac
>            Reporter: Ulrich Kramer
>            Priority: Major
>
> The following unit test for {{JdbcAdapterTest}} fails:
> {code:java}
>   @Test void testOffset() {
>     CalciteAssert.model(FoodmartSchema.FOODMART_MODEL)
>         .query("select * from \"sales_fact_1997\" limit 10 offset 20")
>         .explainContains("PLAN=JdbcToEnumerableConverter\n" +
>             "  JdbcSort(offset=[20], fetch=[10])\n" +
>             "    JdbcTableScan(table=[[foodmart, sales_fact_1997]])")
>         .runs();
>   }
> {code}
> For an offset less than 13, an efficient plan is created. With an offset above 13, the plan looks like this:
> {code}
> EnumerableLimit(offset=[20], fetch=[10])
>   JdbcToEnumerableConverter
>     JdbcTableScan(table=[[foodmart, sales_fact_1997]])
> {code}
> which can lead to enormous latency times, since the entire table is loaded via JDBC.



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