Amazon Redshift
Database Developer Guide

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Step 2: Test System Performance to Establish a Baseline

As you test system performance before and after tuning your tables, you will record the following details:

  • Load time

  • Storage use

  • Query performance

The examples in this tutorial are based on using a four-node dw2.large cluster. Your results will be different, even if you use the same cluster configuration. System performance is influenced by many factors, and no two systems will perform exactly the same.

You will record your results using the following benchmarks table.

Benchmark Before After
Load time (five tables)
Storage Use
Total storage
Query execution time
Query 1
Query 2
Query 3
Total execution time

To Test System Performance to Establish a Baseline

  1. Note the cumulative load time for all five tables and enter it in the benchmarks table in the Before column.

    This is the value you noted in the previous step.

  2. Record storage use.

    Determine how many 1 MB blocks of disk space are used for each table by querying the STV_BLOCKLIST table and record the results in your benchmarks table.

    select as table, count(*) as mb from stv_blocklist, stv_tbl_perm where stv_blocklist.tbl = and stv_blocklist.slice = stv_tbl_perm.slice and in ('lineorder','part','customer','dwdate','supplier') group by order by 1 asc;

    Your results should look similar to this:

    table | mb ----------+------ customer | 384 dwdate | 160 lineorder | 51024 part | 200 supplier | 152
  3. Test query performance.

    The first time you run a query, Amazon Redshift compiles the code, and then sends compiled code to the compute nodes. When you compare the execution times for queries, you should not use the results for the first time you execute the query. Instead, compare the times for the second execution of each query. For more information, see Factors Affecting Query Performance.


    To reduce query execution time and improve system performance, Amazon Redshift caches the results of certain types of queries in memory on the leader node. When result caching is enabled, subsequent queries run much faster, which invalidates performance comparisons.

    To disable result caching for the current session, set the enable_result_cache_for_session parameter to off, as shown following.

    set enable_result_cache_for_session to off;

    Run the following queries twice to eliminate compile time. Record the second time for each query in the benchmarks table.

    -- Query 1 -- Restrictions on only one dimension. select sum(lo_extendedprice*lo_discount) as revenue from lineorder, dwdate where lo_orderdate = d_datekey and d_year = 1997 and lo_discount between 1 and 3 and lo_quantity < 24; -- Query 2 -- Restrictions on two dimensions select sum(lo_revenue), d_year, p_brand1 from lineorder, dwdate, part, supplier where lo_orderdate = d_datekey and lo_partkey = p_partkey and lo_suppkey = s_suppkey and p_category = 'MFGR#12' and s_region = 'AMERICA' group by d_year, p_brand1 order by d_year, p_brand1; -- Query 3 -- Drill down in time to just one month select c_city, s_city, d_year, sum(lo_revenue) as revenue from customer, lineorder, supplier, dwdate where lo_custkey = c_custkey and lo_suppkey = s_suppkey and lo_orderdate = d_datekey and (c_city='UNITED KI1' or c_city='UNITED KI5') and (s_city='UNITED KI1' or s_city='UNITED KI5') and d_yearmonth = 'Dec1997' group by c_city, s_city, d_year order by d_year asc, revenue desc;

    Your results for the second time will look something like this:

    SELECT executed successfully Execution time: 6.97s (Statement 1 of 3 finished) SELECT executed successfully Execution time: 12.81s (Statement 2 of 3 finished) SELECT executed successfully Execution time: 13.39s (Statement 3 of 3 finished) Script execution finished Total script execution time: 33.17s

The following benchmarks table shows the example results for the cluster used in this tutorial.

Benchmark Before After
Load time (five tables) 10m 23s
Storage Use
PART 200
Total storage 51920
Query execution time
Query 1 6.97
Query 2 12.81
Query 3 13.39
Total execution time 33.17

Next Step

Step 3: Select Sort Keys