How to find out if the Teradata Statistics we created for a specific workload are used?
We know that Teradata statistics can have a big impact on how efficiently SQL queries are executed.
So what we need is a protocol that provides us with precisely this information.
Statistics can be collected on various objects (tables, join index, etc.). When we create statistics, as a performance tuner, we want to know if they are being used because statistics that are not needed cause unnecessary resource consumption by collecting them.
The Solution: Logging the Detailed Information with StatUseCountV
Teradata offers us the possibility to find out exactly this information. For this, DBQL UseCount logging and StatusUsage logging must be activated.
Since the USECOUNT logging consumes resources, we recommend not activating it for all databases, but only for analysis purposes on the specific ones.
Enabling the logging for StatUseCountV and Object Use Counts
In our example, we enable logging only for our test database DWHPRO:
-- EnableUse Counts on database DWHPRO only BEGIN QUERY LOGGING WITH USECOUNT ON DWHPRO; -- Enable StatsUsage Logging for user DWHPRO_ADMIN BEGIN QUERY LOGGING WITH STATSUSAGE ON DWHPRO_ADMIN;
Please consider that StatusUsage Logging can’t be defined on the database level. Any attempt will lead to this error:
BEGIN QUERY LOGGING WITH STATSUSAGE ON DWHPRO; REPLACE QUERY LOGGING Failed.  Syntax error: Only USECOUNT option allowed with databases.
Example Query with Statistics Logging
In the example below, you can see how to identify the usage of the statistics in the DBC.StatUseCountV view:
COLLECT STATISTICS COLUMN(a) ON DWHPRO.StatisticsExample; SELECT * FROM DWHPRO.StatisticsExample WHERE a = 1; SELECT * FROM dbc.StatUseCountV;