Complex Select queries

Complex database queries can put a 100% load on the resources of the database server for a long time. This obstructs the workflow of other users or makes it impossible.

The types of complex queries are as follows:

• suboptimal queries in dynamic folders, dashboard blocks
• complex analytical selections in dashboard blocks

You can execute complex Select queries using the following means:

• a dedicated query pool (available for Microsoft SQL Server Enterprise Edition)
• a read-only replica

These ways to execute complex Select queries let you:

• limit resources the database server dedicates to complex Select query processing
• reduce the impact of complex Select query processing on the workflow of other users and the operation of other parts of Creatio

Dedicated query pool 

The purpose of a dedicated query pool is to process complex Select queries that are not part of the transaction and are externalized to a dedicated pool.

1. Set up the connection of a dedicated query pool 

Microsoft SQL Server lets you limit resource allocation using the built-in Resource Governor tool. The Resource Governor rates connections based on the information about the connection, not a particular query. The impact of the tool is barely noticeable on an idle server and short queries. The effect of the Resource Governor is observable when the database server has a 100% load and a complex query takes a long time to execute.

To set up the connection of a dedicated query pool, open the ConnectionStrings.config configuration file and add the _Limited suffix to the App or Application Name property. This setting enables a special connection that divides the queries into simple and potentially complex.

The connection types are as follows:

• If you do not specify a value for the App property in the connection string of the ConnectionStrings.config configuration file, Creatio will use default connections. The default generic connection is ".Net SqlClient DataProvider," the default connection of a dedicated query pool is ".Net SqlClient DataProvider_Limited."

• If you specify "creatio" for the App property in the connection string of the ConnectionStrings.config configuration file, Creatio will replace the connection property of the dedicated query pool with "creatio_Limited."

  Example of the set up App property of the connection string

  <add name="db" connectionString="App=creatio; Data Source=dbserver\mssql2016; Initial Catalog=BpmonlineSolution; Persist Security Info=True; MultipleActiveResultSets=True; Integrated Security=SSPI; Pooling = true; Max Pool Size = 100; Async = true; Connection Timeout=500" />
  

As a result, Creatio adds more database connections when you load dashboards or filter sections using dynamic folders. Unlike main connections, the names of these connections contain the _Limited suffix.

2. Enable the dedicated query pool functionality 

To enable the dedicated query pool functionality, set the UseQueryKinds key of the <appSettings> element in the ..\Terrasoft.WebApp\Web.config file to true. The UseQueryKinds key lets you send queries from dashboards and dynamic folders to connections whose names contain the _Limited suffix.

<add key="UseQueryKinds" value="true" />

3. Set up the Resource Governor tool 

The setup of the Resource Governor tool involves the setup of the groups and pool.

To set up the Resource Governor tool, execute the SQL script.

ALTER RESOURCE POOL poolLimited WITH (
    MAX_CPU_PERCENT = 20,
    MIN_CPU_PERCENT = 0 
    -- REQUEST_MAX_MEMORY_GRANT_PERCENT = value 
    -- REQUEST_MAX_CPU_TIME_SEC = value 
    -- REQUEST_MEMORY_GRANT_TIMEOUT_SEC = value 
    -- MAX_DOP = value 
    -- GROUP_MAX_REQUESTS = value 
);
GO 
--- Create a workload group for off-hours processing 
--- and configure the relative importance.
    CREATE WORKLOAD GROUP groupLimited WITH (IMPORTANCE = LOW) USING poolLimited
GO ALTER RESOURCE GOVERNOR RECONFIGURE;
GO

Learn more about setting up the tool in the official Resource Governor documentation.

The classifier function that returns the group name is run for each new connection.

USE [master]
GO
    
ALTER FUNCTION [dbo].[fnProtoClassifier]()
    RETURNS sysname
    WITH SCHEMABINDING
AS
BEGIN
    IF(app_name() like '%_Limited')
    BEGIN
        RETURN N'groupLimited'
    END
    RETURN N'default'
END;

Read-only replica 

Since version 7.18.4, Creatio supports reading data from a read-only replica. The purpose of a read-only replica is to process complex Select queries.

Creatio can redirect the following queries:

• Custom SelectQuery from Creatio UI.
• Select queries from the back-end. For example, the Script task process element.

Similar to a dedicated query pool, a read-only replica only accepts Select queries that are not part of the transaction. Creatio supports only a single read-only replica.

Learn more about setting up a read-only replica in the user documentation: Process complex database queries faster.

Execute a complex Select query 

To execute a Select query, retrieve a special DBExecutor by passing the Limited value from the QueryKind enumeration as an additional parameter.

QueryKind is the argument of the EnsureDBConnection() method in the example below. Creatio retrieves the argument value from the ESQ client query and inserts the value into the ESQ server query, as well as the Select query.

using (DBExecutor executor = userConnection.EnsureDBConnection(QueryKind)) {
    /* ... */
};

The EnsureDBConnection(QueryKind.General) call is identical to the EnsureDBConnection() call that does not specify QueryKind.

As a result, if you select the QueryKind.Limited flag in the front-end when you create an instance of the Terrasoft.EntitySchemaQuery class, Creatio will pass the value to the server and assign the query a special DBExecutor that uses a dedicated query pool.

...
getChartDataESQ: function() {
    return this.Ext.create("Terrasoft.EntitySchemaQuery", {
        rootSchema: this.entitySchema,
        queryKind: Terrasoft.QueryKind.LIMITED
    });
},
...