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PODelete very slow
 

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  1. PODelete very slow
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    <p>I need to delete only the first appear of a record. This have a PK (<code>preld_item, IDENTITY</code>).</p> <p>This is the very slow DELETE..</p> <pre><code>DELETE pd FROM preliquidaciones_deta pd WHERE pd.preld_item IN (SELECT MAX(p.preld_item) FROM preliquidaciones_deta p WHERE p.id_preliquidacion = '216' GROUP BY p.id_sds_linea_equipo, p.id_concepto HAVING COUNT(p.id_sds_linea_equipo) &gt; 1) </code></pre> <p>Thanks</p> <p>EDIT:</p> <ul> <li>The table has more than 5 million rows</li> <li><code>id_preliquidacion</code> has a clustered index (pk)</li> </ul> <p>EDIT 2: @vulkanino i think in you answer and i modify the delete...</p> <pre><code>DECLARE @loPreldItem INT DECLARE curItems CURSOR FOR (select max(p.preld_item) from preliquidaciones_deta p where p.id_preliquidacion = '216' group by p.id_sds_linea_equipo, p.id_concepto having count(p.id_sds_linea_equipo) &gt; 1) OPEN curItems FETCH NEXT FROM curItems INTO @loPreldItem WHILE @@FETCH_STATUS = 0 BEGIN DELETE FROM preliquidaciones_deta WHERE preld_item = @loPreldItem FETCH NEXT FROM curItems INTO @loPreldItem END CLOSE curItems DEALLOCATE curItems </code></pre> <p>This works best but continue slow</p> <p>EDIT 3: The execution plan of the first delete</p> <pre><code>delete from preliquidaciones_deta where preld_item in ( select max(preld_item) from preliquidaciones_deta where id_preliquidacion = '216' group by id_sds_linea_equipo, id_concepto, preld_nse, preld_linea having count(id_preliquidacion) &gt; 1) |--Assert(WHERE:(CASE WHEN NOT [Expr1018] IS NULL THEN (0) ELSE CASE WHEN NOT [Expr1019] IS NULL THEN (1) ELSE NULL END END)) |--Nested Loops(Left Semi Join, OUTER REFERENCES:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item]), DEFINE:([Expr1019] = [PROBE VALUE])) |--Nested Loops(Left Semi Join, OUTER REFERENCES:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item]), DEFINE:([Expr1018] = [PROBE VALUE])) | |--Clustered Index Delete(OBJECT:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[PK_preliquidaciones_deta]), OBJECT:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[IX_id_sds]), OBJECT:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[IX_id_sds_linea_equipo])) | | |--Top(ROWCOUNT est 0) | | |--Sort(DISTINCT ORDER BY:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item] ASC)) | | |--Nested Loops(Inner Join, OUTER REFERENCES:([Expr1007]) OPTIMIZED) | | |--Filter(WHERE:([Expr1006]&gt;(1))) | | | |--Compute Scalar(DEFINE:([Expr1006]=CONVERT_IMPLICIT(int,[Expr1023],0))) | | | |--Stream Aggregate(GROUP BY:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[id_sds_linea_equipo], [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[id_concepto], [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_nse], [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_linea]) DEFINE:([Expr1023]=Count(*), [Expr1007]=MAX([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item]))) | | | |--Sort(ORDER BY:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[id_sds_linea_equipo] ASC, [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[id_concepto] ASC, [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_nse] ASC, [data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_linea] ASC)) | | | |--Clustered Index Scan(OBJECT:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[PK_preliquidaciones_deta]), WHERE:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[id_preliquidacion]='216')) | | |--Clustered Index Seek(OBJECT:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[PK_preliquidaciones_deta]), SEEK:([data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item]=[Expr1007]) ORDERED FORWARD) | |--Clustered Index Scan(OBJECT:([data_dealernet_lucom].[dbo].[liquidaciones_deta].[PK_liquidaciones_deta]), WHERE:([data_dealernet_lucom].[dbo].[liquidaciones_deta].[preld_item]=[data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item])) |--Table Scan(OBJECT:([data_dealernet_lucom].[dbo].[liquidaciones_diferidas]), WHERE:([data_dealernet_lucom].[dbo].[liquidaciones_diferidas].[preld_item]=[data_dealernet_lucom].[dbo].[preliquidaciones_deta].[preld_item])) </code></pre>
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      1. PODelete very slow
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    1. COHow about any of the other columns appearing in contidions or as grouping criteria like preld_item, id_sds_linea_equipo, d_concepto, do they have a non clustered index?
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    2. COyep, they have a nonclustered index, without that the subquery is very slow too
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