Performance problem with more than one COUNT(DISTINCT ...) in a query

Question

Hi,
(I hope this is the good forum).
In the following query, I have 2 Count Distinct on 2 different fields of the same table.  Execution time is okay (2 s) with one or the other COUNT(DISCTINCT ...) in the SELECT clause, but is not tolerable (12 s) with both together in the query! I have
a similar case with 3 counts: 4 s each, 36 s when together!
I've looked at the execution plan, and it seems that with two count distinct, SQL server sorts the table twice before joining the results.
I do not have much experience with SQL server optimization, and I don't know what to improve and how. The SQL is generated by Business Objects, I have few possibilities to tune it. The most direct way would be to execute 2 different queries, but I'd like
to avoid it.
Any advice?
SELECT
  DIM_MOIS.DATE_DEBUT_MOIS,
  DIM_MOIS.NUM_ANNEE_MOIS,
  DIM_DEMANDE_SCD.CAT_DEMANDE,
  DIM_APPLICATION.LIB_APPLICATION,
  DIM_DEMANDE_SCD.CAT_DEMANDE ,
  count(distinct FAITS_DEMANDE.NB_DEMANDE_FLUX),
  count(distinct FAITS_DEMANDE.NB_DEMANDE_RESOL_NIV1)
FROM
  ALIM_SID.DIM_MOIS INNER JOIN ALIM_SID.DIM_JOUR ON (DIM_JOUR.SEQ_MOIS=DIM_MOIS.SEQ_MOIS)
   INNER JOIN ALIM_SID.FAITS_DEMANDE ON (FAITS_DEMANDE.SEQ_JOUR=DIM_JOUR.SEQ_JOUR)
   INNER JOIN ALIM_SID.DIM_APPLICATION ON (FAITS_DEMANDE.SEQ_APPLICATION=DIM_APPLICATION.SEQ_APPLICATION)
   INNER JOIN ALIM_SID.DIM_DEMANDE_SCD ON (FAITS_DEMANDE.SEQ_DEMANDE_SCD=DIM_DEMANDE_SCD.SEQ_DEMANDE_SCD)
WHERE
  ( ( DIM_MOIS.NUM_ANNEE_MOIS ) >201301
GROUP BY
  DIM_MOIS.DATE_DEBUT_MOIS,
  DIM_MOIS.NUM_ANNEE_MOIS,
  DIM_DEMANDE_SCD.CAT_DEMANDE,
  DIM_APPLICATION.LIB_APPLICATION

Answer 1

Here is the script, nothing original. Hope this helps.
-- Fact table :
-- foreign keys begin by FK_,
-- measures to counted (COUNT DISTINCT) begin with NB_
CREATE TABLE [ALIM_SID].[FAITS_DEMANDE](
    [SEQ_JOUR] [int] NOT NULL,
    [SEQ_DEMANDE] [int] NOT NULL,
    [SEQ_DEMANDE_SCD] [int] NOT NULL,
    [SEQ_APPLICATION] [int] NOT NULL,
    [SEQ_INTERVENANT] [int] NOT NULL,
    [SEQ_SERVICE_RESPONSABLE] [int] NOT NULL,
    [NB_DEMANDE_FLUX] [int] NULL,
    [NB_DEMANDE_STOCK] [int] NULL,
    [NB_DEMANDE_RESOLUE] [int] NULL,
    [NB_DEMANDE_LIVREE] [int] NULL,
    [NB_DEMANDE_MEP] [int] NULL,
    [NB_DEMANDE_RESOL_NIV1] [int] NULL,
 CONSTRAINT [PK_FAITS_DEMANDE] PRIMARY KEY CLUSTERED
    [SEQ_JOUR] ASC,
    [SEQ_DEMANDE] ASC,
    [SEQ_DEMANDE_SCD] ASC,
    [SEQ_APPLICATION] ASC,
    [SEQ_INTERVENANT] ASC,
    [SEQ_SERVICE_RESPONSABLE] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
 CONSTRAINT [AK_AK_FAITS_DEMANDE_FAITS_DE] UNIQUE NONCLUSTERED
    [SEQ_JOUR] ASC,
    [SEQ_DEMANDE] ASC,
    [SEQ_DEMANDE_SCD] ASC,
    [SEQ_APPLICATION] ASC,
    [SEQ_INTERVENANT] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_APPLICATION] FOREIGN KEY([SEQ_APPLICATION])
REFERENCES [ALIM_SID].[DIM_APPLICATION] ([SEQ_APPLICATION])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_APPLICATION]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_DEMANDE] FOREIGN KEY([SEQ_DEMANDE])
REFERENCES [ALIM_SID].[DIM_DEMANDE] ([SEQ_DEMANDE])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_DEMANDE]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_DEMANDE_SCD] FOREIGN KEY([SEQ_DEMANDE_SCD])
REFERENCES [ALIM_SID].[DIM_DEMANDE_SCD] ([SEQ_DEMANDE_SCD])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_DEMANDE_SCD]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_INTERVENANT] FOREIGN KEY([SEQ_INTERVENANT])
REFERENCES [ALIM_SID].[DIM_INTERVENANT] ([SEQ_INTERVENANT])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_INTERVENANT]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_JOUR] FOREIGN KEY([SEQ_JOUR])
REFERENCES [ALIM_SID].[DIM_JOUR] ([SEQ_JOUR])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_JOUR]
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE]  WITH CHECK ADD  CONSTRAINT [FK_FAITS_DEMANDE_DIM_SERVICE_RESPONSABLE] FOREIGN KEY([SEQ_SERVICE_RESPONSABLE])
REFERENCES [ALIM_SID].[DIM_SERVICE] ([SEQ_SERVICE])
GO
ALTER TABLE [ALIM_SID].[FAITS_DEMANDE] CHECK CONSTRAINT [FK_FAITS_DEMANDE_DIM_SERVICE_RESPONSABLE]
GO
-- not shown : extended properties
-- One of the dimension  tables (they all have a primary key named SEQ_)
CREATE TABLE [ALIM_SID].[DIM_JOUR](
    [SEQ_JOUR] [int] IDENTITY(1,1) NOT NULL,
    [SEQ_ANNEE] [int] NOT NULL,
    [SEQ_MOIS] [int] NOT NULL,
    [DATE_JOUR] [date] NULL,
    [CODE_ANNEE] [varchar](25) NULL,
    [CODE_MOIS] [varchar](25) NULL,
    [CODE_SEMAINE_ISO] [varchar](25) NULL,
    [CODE_JOUR_ANNEE] [varchar](25) NULL,
    [CODE_ANNEE_JOUR] [varchar](25) NULL,
    [LIB_JOUR] [varchar](25) NULL,
    [LIB_JOUR_COURT] [varchar](25) NULL,
    [JOUR_OUVRE] [tinyint] NULL,
    [JOUR_CHOME] [tinyint] NULL,
 CONSTRAINT [PK_DIM_JOUR] PRIMARY KEY CLUSTERED
    [SEQ_JOUR] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [ALIM_SID].[DIM_JOUR]  WITH CHECK ADD  CONSTRAINT [FK_DIM_JOUR_DIM_ANNEE] FOREIGN KEY([SEQ_ANNEE])
REFERENCES [ALIM_SID].[DIM_ANNEE] ([SEQ_ANNEE])
GO
ALTER TABLE [ALIM_SID].[DIM_JOUR] CHECK CONSTRAINT [FK_DIM_JOUR_DIM_ANNEE]
GO
ALTER TABLE [ALIM_SID].[DIM_JOUR]  WITH CHECK ADD  CONSTRAINT [FK_DIM_JOUR_DIM_MOIS] FOREIGN KEY([SEQ_MOIS])
REFERENCES [ALIM_SID].[DIM_MOIS] ([SEQ_MOIS])
GO
ALTER TABLE [ALIM_SID].[DIM_JOUR] CHECK CONSTRAINT [FK_DIM_JOUR_DIM_MOIS]
GO