Managing directed queries

• 1: Getting directed queries
• 2: Identifying active directed queries
• 3: Activating and deactivating directed queries
• 4: Exporting directed queries from the catalog
• 5: Dropping directed queries

1 - Getting directed queries

You can obtain catalog information about directed queries in two ways:

• Use GET DIRECTED QUERY.

• Query system table DIRECTED_QUERIES.

GET DIRECTED QUERY

GET DIRECTED QUERY queries the system table DIRECTED_QUERIES on the specified input query. It returns details of all directed queries that map to the input query.

The following GET DIRECTED QUERY statement returns the directed query that maps to the following input query, findEmployeesCityJobTitle_OPT:

=> GET DIRECTED QUERY SELECT employee_first_name, employee_last_name from employee_dimension where employee_city='Boston' AND job_title='Cashier' order by employee_last_name, employee_first_name;
-[ RECORD 1 ]---+
query_name      | findEmployeesCityJobTitle_OPT
is_active       | t
vertica_version | Vertica Analytic Database v11.0.1-20210815
comment         | Optimizer-generated directed query
creation_date   | 2021-08-20 14:53:42.323963
annotated_query | SELECT /*+verbatim*/  employee_dimension.employee_first_name, employee_dimension.employee_last_name FROM public.employee_dimension employee_dimension/*+projs('public.employee_dimension')*/ WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6) /*+:v(1)*/) AND (employee_dimension.job_title = 'Cashier'::varchar(7) /*+:v(2)*/)) ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name

DIRECTED_QUERIES

You can query the system table DIRECTED_QUERIES directly. For example:

=> SELECT query_name, is_active FROM V_CATALOG.DIRECTED_QUERIES WHERE query_name ILIKE '%findEmployeesCityJobTitle%';
          query_name           | is_active
-------------------------------+-----------
 findEmployeesCityJobTitle_OPT | t
(1 row)

2 - Identifying active directed queries

Multiple directed queries can map to the same input query. The is_active column in system table DIRECTED_QUERIES identifies directed queries that are active. If multiple directed queries are active for the same input query, the optimizer uses the first one to be created. In that case, you can use EXPLAIN to identify which directed query is active.

The following query on DIRECTED_QUERIES finds all active directed queries where the input query contains the name of the queried table employee_dimension:

=> SELECT * FROM directed_queries WHERE input_query ILIKE ('%employee_dimension%') AND is_active='t';
-[ RECORD 1 ]------+
query_name         | findEmployeesCityJobTitle_OPT
is_active          | t
vertica_version    | Vertica Analytic Database v11.0.1-20210815
comment            | Optimizer-generated directed query
save_plans_version | 0
username           | dbadmin
creation_date      | 2021-08-20 14:53:42.323963
since_date         |
input_query        | SELECT employee_dimension.employee_first_name, employee_dimension.employee_last_name FROM public.employee_dimension WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6) /*+:v(1)*/) AND (employee_dimension.job_title = 'Cashier'::varchar(7) /*+:v(2)*/)) ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name
annotated_query    | SELECT /*+verbatim*/  employee_dimension.employee_first_name, employee_dimension.employee_last_name FROM public.employee_dimension employee_dimension/*+projs('public.employee_dimension')*/ WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6) /*+:v(1)*/) AND (employee_dimension.job_title = 'Cashier'::varchar(7) /*+:v(2)*/)) ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name

If you run EXPLAIN on the input query, it returns with a query plan that confirms use of findEmployeesCityJobTitle_OPT as the active directed query:

=> EXPLAIN SELECT employee_first_name, employee_last_name FROM employee_dimension WHERE employee_city='Boston' AND job_title ='Cashier' ORDER BY employee_last_name, employee_first_name;

 The following active directed query(query name: findEmployeesCityJobTitle_OPT) is being executed:
 SELECT /*+verbatim*/  employee_dimension.employee_first_name, employee_dimension.employee_last_name FROM public.employee_dimension employee_dimension/*+projs('public.employee_dimension')*/ WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6)) AND (employee_dimension.job_title = 'Cashier'::varchar(7))) ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name

3 - Activating and deactivating directed queries

The optimizer uses only directed queries that are active. If multiple directed queries share the same input query, the optimizer uses the first one to be created.

You activate and deactivate directed queries with ACTIVATE DIRECTED QUERY and DEACTIVATE DIRECTED QUERY, respectively. For example, the following ACTIVATE DIRECTED QUERY statement deactivates RegionalSalesProducts_JoinTables and activates RegionalSalesProduct:

=> DEACTIVATE DIRECTED QUERY RegionalSalesProducts_JoinTables;
DEACTIVATE DIRECTED QUERY;
=> ACTIVATE DIRECTED QUERY RegionalSalesProduct;
ACTIVATE DIRECTED QUERY;

Vertica uses the active directed query for a given query across all sessions until it is explicitly deactivated by DEACTIVATE DIRECTED QUERY or removed from storage by DROP DIRECTED QUERY. If a directed query is active at the time of database shutdown, Vertica automatically reactivates it when you restart the database.

After a direct query is deactivated, the query optimizer handles subsequent invocations of the input query by using another directed query, if one is available. Otherwise, it generates its own query plan.

4 - Exporting directed queries from the catalog

Before upgrading to a new version of Vertica, you can export directed queries for those queries whose optimal performance is critical to your system:

1. Use EXPORT_CATALOG with the argument DIRECTED_QUERIES to export from the database catalog all current directed queries and their current activation status:

   => SELECT EXPORT_CATALOG('../../export_directedqueries', 'DIRECTED_QUERIES');
   EXPORT_CATALOG
   -------------------------------------
   Catalog data exported successfully
   

2. EXPORT_CATALOG creates a script to recreate the directed queries, as in the following example:

   SAVE QUERY SELECT employee_dimension.employee_first_name, employee_dimension.employee_last_name FROM public.employee_dimension WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6) /*+:v(1)*/) AND (employee_dimension.job_title = 'Cashier'::varchar(7) /*+:v(2)*/)) ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name;
   CREATE DIRECTED QUERY CUSTOM findEmployeesCityJobTitle_OPT COMMENT 'Optimizer-generated directed query' OPTVER 'Vertica Analytic Database v11.0.1-20210815' PSDATE '2021-08-20 14:53:42.323963' SELECT /*+verbatim*/  employee_dimension.employee_first_name, employee_dimension.employee_last_name
   FROM public.employee_dimension employee_dimension/*+projs('public.employee_dimension')*/
   WHERE ((employee_dimension.employee_city = 'Boston'::varchar(6) /*+:v(1)*/) AND (employee_dimension.job_title = 'Cashier'::varchar(7) /*+:v(2)*/))
   ORDER BY employee_dimension.employee_last_name, employee_dimension.employee_first_name;
   ACTIVATE DIRECTED QUERY findEmployeesCityJobTitle_OPT;
   

   Note

   The script that EXPORT_CATALOG creates specifies to recreate all directed queries with CREATE DIRECTED QUERY CUSTOM, regardless of how they were created originally.

3. After the upgrade is complete, remove each directed query from the database catalog with DROP DIRECTED QUERY. Alternatively, edit the export script and insert a DROP DIRECTED QUERY statement before each CREATE DIRECTED QUERY statement. For example, you might modify the script generated earlier with the changes shown in bold:

   SAVE QUERY SELECT employee_dimension.employee_first_name, ... ;
   DROP DIRECTED QUERY findEmployeesCityJobTitle_OPT;
   CREATE DIRECTED QUERY CUSTOM findEmployeesCityJobTitle_OPT COMMENT 'Optimizer-generated ... ;
   ACTIVATE DIRECTED QUERY findEmployeesCityJobTitle_OPT;
   

4. When you run this script, Vertica recreates the directed queries and restores their activation status:

   => \i /home/dbadmin/export_directedqueries
   SAVE QUERY
   DROP DIRECTED QUERY
   CREATE DIRECTED QUERY
   ACTIVATE DIRECTED QUERY
   

5 - Dropping directed queries

DROP DIRECTED QUERY removes the specified directed query from the database catalog. If the directed query is active, Vertica deactivates it before removal.

For example:

=> DROP DIRECTED QUERY findBostonCashiers_CUSTOM;
DROP DIRECTED QUERY