Help Center/ Data Warehouse Service/ Standard Data Warehouse (9.1.0.x)/ DWS Performance Tuning/ SQL Tuning Examples/ Cases: Modifying Statements That Cannot Be Pushed Down/ Case: Main Plan Exec on CN and Subplan Exec on DN Can Not Be Shipped
Updated on 2026-05-29 GMT+08:00
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Case: Main Plan Exec on CN and Subplan Exec on DN Can Not Be Shipped

Possible Cause

Possible cause: The main query in the complex statement does not involve user tables, but the related subquery does.

Case 1: Using the Dimension Table DUAL As the Main Query's Source Table

Original statement

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SELECT 
    1 
FROM (SELECT 1 
    FROM dual 
    WHERE -2 = -2
    AND 202210 IN(SELECT /*+ PARALLEL(8) */ 
        DISTINCT PERIOD_ID
        FROM DWICBG_VI.CBGDWR_PSI_FIN_OVER_INV_V T 
        WHERE T.LAST_MODIFIED_DATE > (SELECT NVL(MAX(LAST_MODIFIED_DATE), TRUNC(SYSDATE) - 1) from FIN_DWB_MSS.DWB_MSS_PSI_FIN_OVER_INV_M_F) AND T.LAST_MODIFIED_DATE <= (SELECT  TRUNC(SYSDATE) + 1) 
    )
) t LIMIT 1

Rewritten statement

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SELECT 
    1 
FROM(SELECT 1 
    FROM (SELECT /*+ PARALLEL(8) */
            DISTINCT PERIOD_ID
        FROM DWICBG_VI.CBGDWR_PSI_FIN_OVER_INV_V T 
        WHERE T.LAST_MODIFIED_DATE > (SELECT NVL(MAX(LAST_MODIFIED_DATE), TRUNC(SYSDATE) - 1) from FIN_DWB_MSS.DWB_MSS_PSI_FIN_OVER_INV_M_F) AND T.LAST_MODIFIED_DATE <= (SELECT  TRUNC(SYSDATE) + 1) 
    ) t(PERIOD_ID) 
where PERIOD_ID = 202210
) t LIMIT 1

Modification comparison

Parent Topic: Cases: Modifying Statements That Cannot Be Pushed Down