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173 lines
7.3 KiB
ReStructuredText
173 lines
7.3 KiB
ReStructuredText
.. _trigger_function_dialog:
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********************************
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`Trigger Function Dialog`:index:
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********************************
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Use the *Trigger function* dialog to create or manage a trigger_function. A
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trigger function defines the action that will be invoked when a trigger fires.
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The *Trigger function* dialog organizes the development of a trigger function
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through the following dialog tabs: *General*, *Definition*, *Code*, *Options*,
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*Parameters* and *Security*. The *SQL* tab displays the SQL code generated by
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dialog selections.
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.. image:: images/trigger_function_general.png
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:alt: Trigger function dialog general tab
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:align: center
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Use the fields in the *General* tab to identify the trigger function:
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* Use the *Name* field to add a descriptive name for the trigger function. The
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name will be displayed in the *pgAdmin* tree control. Please note that trigger
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functions will be invoked in alphabetical order.
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* Use the drop-down listbox next to *Owner* to select the role that will own the
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trigger function.
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* Select the name of the schema in which the trigger function will reside from
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the drop-down listbox in the *Schema* field.
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* Store notes about the trigger function in the *Comment* field.
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Click the *Definition* tab to continue.
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.. image:: images/trigger_function_definition.png
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:alt: Trigger function dialog definition tab
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:align: center
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Use the fields in the *Definition* tab to define the trigger function:
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* Use the drop-down listbox next to *Return type* to specify the pseudotype that
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is associated with the trigger function:
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* Select *trigger* if you are creating a DML trigger.
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* Select *event_trigger* if you are creating a DDL trigger.
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* Use the drop-down listbox next to *Language* to select the implementation
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language. The default is *plpgsql*.
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Click the *Code* tab to continue.
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.. image:: images/trigger_function_code.png
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:alt: Trigger function dialog code tab
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:align: center
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* Use the *Code* field to write the code that will execute when the trigger
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function is called.
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Click the *Options* tab to continue.
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.. image:: images/trigger_function_options.png
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:alt: Trigger function dialog options tab
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:align: center
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Use the fields in the *Options* tab to describe or modify the action of the
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trigger function:
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* Use the drop-down listbox next to *Volatility* to select one of the following:
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* *VOLATILE* indicates that the trigger function value can change even
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within a single table scan.
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* *STABLE* indicates that the trigger function cannot modify the database,
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and that within a single table scan it will consistently return the same
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result for the same argument values.
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* *IMMUTABLE* indicates that the trigger function cannot modify the database
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and always returns the same result when given the same argument values.
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* Move the *Returns a Set?* switch to indicate if the trigger function returns a
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set that includes multiple rows. The default is *No*.
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* Move the *Strict?* switch to indicate if the trigger function always returns
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NULL whenever any of its arguments are NULL. If *Yes*, the function is not
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executed when there are NULL arguments; instead a NULL result is assumed
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automatically. The default is *No*.
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* Move the *Security of definer?* switch to specify that the trigger function
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is to be executed with the privileges of the user that created it. The default
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is *No*.
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* Move the *Window?* switch to indicate that the trigger function is a window
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function rather than a plain function. The default is *No*. This is currently
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only useful for trigger functions written in C.
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* Use the *Estimated cost* field to specify a positive number representing the
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estimated execution cost for the trigger function, in units of
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cpu_operator_cost. If the function returns a set, this is the cost per
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returned row.
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* Use the *Estimated rows* field to specify a positive number giving the
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estimated number of rows that the query planner should expect the trigger
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function to return. This is only allowed when the function is declared to
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return a set. The default assumption is 1000 rows.
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* Move the *Leak proof?* switch to indicate whether the trigger function has
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side effects. The default is *No*. This option can only be set by the
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superuser.
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Click the *Parameters* tab to continue.
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.. image:: images/trigger_function_parameters.png
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:alt: Trigger function dialog parameters tab
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:align: center
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Use the fields in the *Parameters* tab to specify settings that will be applied
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when the trigger function is invoked. Click the *Add* icon (+) to add a
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*Name*/*Value* pair to the table below.
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* Use the drop-down listbox in the *Name* field to select a parameter.
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* Use the *Value* field to specify the value that will be associated with the
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selected parameter. This field is context-sensitive.
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Click the *Add* icon (+) to set additional parameters; to discard a parameter,
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click the trash icon to the left of the row and confirm deletion in the *Delete
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Row* popup.
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Click the *Security* tab to continue.
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.. image:: images/trigger_function_security.png
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:alt: Trigger function dialog security tab
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:align: center
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Use the *Security* tab to assign privileges and define security labels.
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Use the *Privileges* panel to assign usage privileges for the trigger function
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to a role. Click the *Add* icon (+) to add a role to the table.
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* Select the name of the role from the drop-down listbox in the *Grantee* field.
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* Click inside the *Privileges* field. Check the boxes to the left of one or
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more privileges to grant the selected privilege to the specified user.
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* The current user, who is the default grantor for granting the privilege, is displayed in the *Grantor* field.
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Click the *Add* icon (+) to assign additional privileges; to discard a
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privilege, click the trash icon to the left of the row and confirm deletion in
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the *Delete Row* popup.
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Use the *Security Labels* panel to define security labels applied to the trigger
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function. Click the *Add* icon (+) to add each security label selection:
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* Specify a security label provider in the *Provider* field. The named provider
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must be loaded and must consent to the proposed labeling operation.
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* Specify a a security label in the *Security Label* field. The meaning of a
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given label is at the discretion of the label provider. PostgreSQL places no
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restrictions on whether or how a label provider must interpret security
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labels; it merely provides a mechanism for storing them.
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Click the *Add* icon (+) to assign additional security labels; to discard a
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security label, click the trash icon to the left of the row and confirm deletion
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in the *Delete Row* popup.
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Click the *SQL* tab to continue.
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Your entries in the *Trigger function* dialog generate a SQL command (see an
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example below). Use the *SQL* tab for review; revisit other tabs to modify the
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SQL command.
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Example
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*******
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The following is an example of the sql command generated by user selections in
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the *Trigger function* dialog:
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.. image:: images/trigger_function_sql.png
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:alt: Trigger function dialog sql tab
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:align: center
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The example shown demonstrates creating a trigger function named *emp_stamp*.
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* Click the *Info* button (i) to access online help.
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* Click the *Save* button to save work.
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* Click the *Close* button to exit without saving work.
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* Click the *Reset* button to restore configuration parameters.
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