WL#6383: Define and Implement API for Triggers
Affects: Server-8.0 — Status: Complete — Priority: Medium
This worklog specifies interfaces of the following object types: - Trigger This interface would enable, - Adding new trigger for a given table. Support PRECEDES/FOLLOWS symantics. - Drop an trigger from a dd::Table. - Find dd::Table object for a given trigger name. This WL would introduce new set of DD API's and does not aim to make server use these API's. A separate WL shall make sql server changes which would stop creating .TRG/TRN file-system files and use DD API's provided by this WL. This worklog mostly follows guidelines from API framework class definitions (see WL#7284 for more info). User Documentation ================== No user-visible changes. No user documentation required.
NF1: No user visible changes.
NOTE: handling of attributes of collection types is described in WL#6380, section "Common API attribute guidelines". NOTE: Dictionary_object, Entity_object, Weak_object are specified in WL#7284. The triggers are implemented as collection of items per dd::Table object. A) The new Trigger DD API interface introduced is, dd::Trigger ========== The dd::Trigger interface represents one trigger. Base interfaces: - Dictionary_object - Entity_object - Weak_object - Collection_item Members: * Common attributes: - Trigger event type. - Trigger action timing. - SQL mode. - Action order. - Trigger creation time. - Trigger alter time. - Action statement - Action statement in UTF8 form. - Trigger definer host and user. * References: - Strong-reference to dd::Table object for which this trigger belongs to. - Weak-reference to the client collation which was in effect when the trigger was created. - Weak-reference to the connection collation which was in effect when the trigger was created. - Weak-reference to the schema collation which was in effect when the trigger was created. B) Interface changes to dd::Table to support Triggers: Following new methods are introduced to dd::Table, - Check if there exists a trigger on dd::Table. virtual bool has_trigger() const = 0; - Get iterator to list of const Trigger objects ordered based on action_order. virtual Trigger_const_iterator *dd::Table::triggers() const = 0; - Get iterator to list of Trigger objects which match given event type and action timing. virtual Trigger_const_iterator *get_triggers( Trigger::enum_action_timing at, Trigger::enum_event_type et) const = 0; - Get iterator to list of non-const Trigger objects ordered based on action_order. virtual Trigger_iterator *dd::Table::triggers() = 0; - Add new trigger virtual Trigger *dd::Table::add_trigger() = 0; - Get Trigger object for the given trigger name. virtual Trigger *dd::Table::get_trigger(const char *name) = 0; - Add new trigger just after the trigger specified in argument. virtual Trigger *dd::Table::add_trigger_following( const Trigger *trigger) = 0; - Add new trigger just before the trigger specified in argument. virtual Trigger *dd::Table::add_trigger_preceding( const Trigger *trigger) = 0; - Drop the given trigger object. virtual void dd::Table::drop_trigger(Trigger *trigger) = 0; C) New API to find the table name for a given trigger name. - Retrieve a table name of a given trigger name and schema id. bool Dictionary_client::get_table_name_by_trigger_name(Object_id schema_id, const std::string &trigger_name, std::string *table_name); D) Steps to perform various trigger operations are, + Steps to add trigger: - Get dd::Table object for which you want to add trigger. - Invoke dd::Table::add_trigger*() API. - Set dd::Trigger attributes. - Store the dd::Table object. All the trigger objects gets stored in mysql.triggers. + Steps to get dd::Table for a given trigger name: - Invoke Dictionary_client::get_table_name_by_trigger_name() with a trigger name to get the table name for which the trigger belongs to. - Make sure you acquire desired MDL lock on table name. - Get dd::Table object using Dictionary_client::acquire<>() API. + Steps to drop trigger: - Follow steps to get dd::Table given trigger name above. - Use dd::Table::get_trigger(
) API to get the dd::Trigger object. - Invoke dd::Table::drop_trigger(Trigger*) to remove the trigger on the Table. - Store dd::Table object, which will remove the trigger from mysql.triggers DD table.
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