Step 3: Optimizing a Table

Selecting a Storage Mode

Sample tables used in this practice are typical multi-column TPC-DS tables where many statistical analysis queries are performed. Therefore, the column storage mode is recommended.

    
         WITH (ORIENTATION = column)

Selecting a Compression Level

No compression ratio is specified in Step 1: Creating an Initial Table and Loading Sample Data, and the low compression ratio is selected by GaussDB(DWS) by default. Specify COMPRESSION to MIDDLE, and compare the result to that when COMPRESSION is set to LOW.

The following is an example of selecting a storage mode and the MIDDLE compression ratio for a table.

   
    
      
      
        CREATE TABLE store_sales
(
    ss_sold_date_sk           integer                       ,
    ss_sold_time_sk           integer                       ,
    ss_item_sk                integer               not null,
    ss_customer_sk            integer                       ,
    ss_cdemo_sk               integer                       ,
    ss_hdemo_sk               integer                       ,
    ss_addr_sk                integer                       ,
    ss_store_sk               integer                       ,
    ss_promo_sk               integer                       ,
    ss_ticket_number          bigint               not null,
    ss_quantity               integer                       ,
    ss_wholesale_cost         decimal(7,2)                  ,
    ss_list_price             decimal(7,2)                  ,
    ss_sales_price            decimal(7,2)                  ,
    ss_ext_discount_amt       decimal(7,2)                  ,
    ss_ext_sales_price        decimal(7,2)                  ,
    ss_ext_wholesale_cost     decimal(7,2)                  ,
    ss_ext_list_price         decimal(7,2)                  ,
    ss_ext_tax                decimal(7,2)                  ,
    ss_coupon_amt             decimal(7,2)                  ,
    ss_net_paid               decimal(7,2)                  ,
    ss_net_paid_inc_tax       decimal(7,2)                  ,
    ss_net_profit             decimal(7,2)                  
) 
WITH (ORIENTATION = column,COMPRESSION=middle);

       

     

   
  

Selecting a Distribution Mode

Based on table sizes provided in Step 2: Testing System Performance of the Initial Table and Establishing a Baseline, set the distribution mode as follows.

Table Name	Number of Rows	Distribution Mode
Store_Sales	287997024	Hash
Date_Dim	73049	Replication
Store	402	Replication
Item	204000	Replication
Time_Dim	86400	Replication
Promotion	1000	Replication
Customer_Demographics	1920800	Hash
Customer_Address	1000000	Hash
Household_Demographics	7200	Replication
Customer	1981703	Hash
Income_Band	20	Replication

Selecting a Distribution Key

If your table is distributed using hash, choose a proper distribution key. You are advised to select a distribution key according to Selecting a Distribution Key.

Select the primary key of each table as the distribution key of the hash table.

Table Name	Number of Records	Distribution Mode	Distribution Key
Store_Sales	287997024	Hash	ss_item_sk
Date_Dim	73049	Replication	-
Store	402	Replication	-
Item	204000	Replication	-
Time_Dim	86400	Replication	-
Promotion	1000	Replication	-
Customer_Demographics	1920800	Hash	cd_demo_sk
Customer_Address	1000000	Hash	ca_address_sk
Household_Demographics	7200	Replication	-
Customer	1981703	Hash	c_customer_sk
Income_Band	20	Replication	-