These icons are displayed in the SQL Server Management Studio when displaying the graphical execution plan and represent operators used by SQL Server to execute statements. For more detailed information, see this Microsoft article on SQL Server 2008 R2.
Execution plans are not displayed for encrypted stored procedures or for triggers.
When we create a sql query and pass that statement to SQL Server, it goes to is the relational engine first. As the sql arrives, it passes through a process that verifies the sql was written correctly and that it is properly formatted. This process is called query parsing. If a query fails to parse correctly because of a typo, then parsing stops and SQL Server returns an error. The output of the Parser process is a parse tree, or query tree. The parse tree represents the logical steps required to execute the requested query. If the T-SQL string is a data definition language (DDL) query, instead of a data manipulation language (DML) statement, it will not be optimized during this process.
If the T-SQL string is a DML statement and it has parsed correctly, the parse tree is passed to a process called the algebrizer. The algebrizer resolves all the names of the various objects, tables, and columns in the query string. The algebrizer outputs a binary called the query processor tree, which is then passed on to the query optimizer. Part of what is passed to the query optimizer is a hash value that represents the query. The query optimizer attempts to find this hash value in it’s history, and if it does then it just uses the previous plan to execute the query. If it doesn’t find a similar hash value, it creates a new query plan. This technique is intended to reduce the overhead required by the query optimizer to generate a new plan for each query.
The query optimizer is a very complicated piece of software that attempts to return query results using the least amount of time possible. Once the results are returned, you can use the execution plan to uncover how the results were generated and potentially make changes to improve the speed of the results. These graphic images can be difficult to understand at first, but it is important that you earn them to provide the best technical support possible.
This example screen shot shows some of the icons which you might see in our execution plans.
Operators that are executed in parallel are displayed with the following parallel process icon above the operator.
The following icons displayed in the graphical execution plan represent the Cursor Logical and Physical Showplan Operators used by SQL Server to execute statements.
|Icon||Cursor physical operator|
The following icons displayed in the graphical execution plan represent the Parallelism Showplan Operator physical operators used by SQL Server to execute statements.
The following icons displayed in the graphical execution plan represent the Transact-SQL language elements used by SQL Server.