Saved Queries

Using the save_query command will both generate and save an execution plan. This allows you to save time when running frequently used complex queries.

Note that the saved execution plan is tightly coupled with the structure of its underlying tables, which means that if one or more of the objects mentioned in the query is modified, the saved query must be re-created.

How Saved Queries Work

Saved queries are compiled when they are created. When a saved query is run, this query plan is used instead of compiling a query plan at query time.

Parameter Support

Query parameters can be used as substitutes for constants expressions in queries.

• Parameters cannot be used to substitute identifiers like column names and table names.

• Query parameters of a string datatype (like TEXT) must be of a fixed length, and can be used in equality checks, but not patterns (e.g. LIKE, RLIKE, etc.)

Creating a Saved Query

A saved query is created using the SAVE_QUERY utility command.

Saving a Simple Query

SELECT SAVE_QUERY('select_all','SELECT * FROM nba');
executed

Saving a Parameterized Query

Parameterized queries, also known as prepared statements, enable the usage of parameters which may be replaced by actual values when executing the query. They are created and managed in application code, primarily to optimize query execution, enhance security, and allow for the reuse of query templates with different parameter values.

SELECT SAVE_QUERY('select_by_weight_and_team','SELECT * FROM nba WHERE Weight > ? AND Team = ?');

Executing Saved Queries

Executing a saved query requires calling it by it’s name in a EXECUTE_SAVED_QUERY statement. A saved query with no parameter is called without parameters.

SELECT EXECUTE_SAVED_QUERY('select_all');
Name                     | Team                   | Number | Position | Age | Height | Weight | College               | Salary
-------------------------+------------------------+--------+----------+-----+--------+--------+-----------------------+---------
Avery Bradley            | Boston Celtics         |      0 | PG       |  25 | 6-2    |    180 | Texas                 |  7730337
Jae Crowder              | Boston Celtics         |     99 | SF       |  25 | 6-6    |    235 | Marquette             |  6796117
John Holland             | Boston Celtics         |     30 | SG       |  27 | 6-5    |    205 | Boston University     |
R.J. Hunter              | Boston Celtics         |     28 | SG       |  22 | 6-5    |    185 | Georgia State         |  1148640
[...]

Executing a saved query with parameters requires specifying the parameters in the order they appear in the query:

SELECT EXECUTE_SAVED_QUERY('select_by_weight_and_team', 240, 'Toronto Raptors');
Name              | Team            | Number | Position | Age | Height | Weight | College     | Salary
------------------+-----------------+--------+----------+-----+--------+--------+-------------+--------
Bismack Biyombo   | Toronto Raptors |      8 | C        |  23 | 6-9    |    245 |             | 2814000
James Johnson     | Toronto Raptors |      3 | PF       |  29 | 6-9    |    250 | Wake Forest | 2500000
Jason Thompson    | Toronto Raptors |      1 | PF       |  29 | 6-11   |    250 | Rider       |  245177
Jonas Valanciunas | Toronto Raptors |     17 | C        |  24 | 7-0    |    255 |             | 4660482

Listing Saved Queries

Saved queries are saved as a database objects. They can be listed in one of two ways:

Using the catalog:

SELECT * FROM sqream_catalog.savedqueries;
name                      | num_parameters
--------------------------+---------------
select_all                |              0
select_by_weight          |              1
select_by_weight_and_team |              2

Using the LIST_SAVED_QUERIES utility function:

SELECT LIST_SAVED_QUERIES();
saved_query
-------------------------
select_all
select_by_weight
select_by_weight_and_team

Dropping a Saved Query

When you’re done with a saved query, or would like to replace it with another, you can drop it with DROP_SAVED_QUERY:

SELECT DROP_SAVED_QUERY('select_all');
executed
SELECT DROP_SAVED_QUERY('select_by_weight_and_team');
executed

SELECT LIST_SAVED_QUERIES();
saved_query
-------------------------
select_by_weight