Item_trigger_field Class Reference

Inheritance diagram for Item_trigger_field:

List of all members.

Public Types
enum	row_version_type { OLD_ROW, NEW_ROW }
Public Member Functions
	Item_trigger_field (Name_resolution_context *context_arg, row_version_type row_ver_arg, const char *field_name_arg, ulong priv, const bool ro)
void	setup_field (THD *thd, TABLE *table, GRANT_INFO *table_grant_info)
enum Type	type () const
bool	eq (const Item *item, bool binary_cmp) const
bool	fix_fields (THD *, Item **)
virtual void	print (String *str, enum_query_type query_type)
table_map	used_tables () const
Field *	get_tmp_table_field ()
Item *	copy_or_same (THD *thd)
Item *	get_tmp_table_item (THD *thd)
void	cleanup ()
Settable_routine_parameter *	get_settable_routine_parameter ()
bool	set_value (THD *thd, Item **it)
Public Attributes
row_version_type	row_version
Item_trigger_field *	next_trg_field
SQL_I_List< Item_trigger_field > *	next_trig_field_list
uint	field_idx
Table_triggers_list *	triggers

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Member Function Documentation

bool Item_trigger_field::eq	(	const Item *	item,
		bool	binary_cmp
	)		const [virtual]

This function is called when:

• Comparing items in the WHERE clause (when doing where optimization)
• When trying to find an ORDER BY/GROUP BY item in the SELECT part
• When matching fields in multiple equality objects (Item_equal)

Reimplemented from Item_field.

bool Item_trigger_field::fix_fields	(	THD *	thd,
		Item **	reference
	)		[virtual]

Resolve the name of a column reference.

The method resolves the column reference represented by 'this' as a column present in one of: FROM clause, SELECT clause, GROUP BY clause of a query Q, or in outer queries that contain Q.

The name resolution algorithm used is (where [T_j] is an optional table name that qualifies the column name):

    resolve_column_reference([T_j].col_ref_i)
    {
      search for a column or derived column named col_ref_i
      [in table T_j] in the FROM clause of Q;

      if such a column is NOT found AND    // Lookup in outer queries.
         there are outer queries
      {
        for each outer query Q_k beginning from the inner-most one
        {
          search for a column or derived column named col_ref_i
          [in table T_j] in the FROM clause of Q_k;

          if such a column is not found
            Search for a column or derived column named col_ref_i
            [in table T_j] in the SELECT and GROUP clauses of Q_k.
        }
      }
    }

Notice that compared to Item_ref::fix_fields, here we first search the FROM clause, and then we search the SELECT and GROUP BY clauses.

Parameters:

[in]	thd	current thread
[in,out]	reference	view column if this item was resolved to a view column

Return values:

TRUE	if error
FALSE	on success

Reimplemented from Item_field.

void Item_trigger_field::print	(	String *	str,
		enum_query_type	query_type
	)		[virtual]

This method is used for to:

• to generate a view definition query (SELECT-statement);
• to generate a SQL-query for EXPLAIN EXTENDED;
• to generate a SQL-query to be shown in INFORMATION_SCHEMA;
• debug.

For more information about view definition query, INFORMATION_SCHEMA query and why they should be generated from the Item-tree,

See also:

mysql_register_view().

Reimplemented from Item_field.

void Item_trigger_field::setup_field	(	THD *	thd,
		TABLE *	table,
		GRANT_INFO *	table_grant_info
	)

Find index of Field object which will be appropriate for item representing field of row being changed in trigger.

Parameters:

thd	current thread context
table	table of trigger (and where we looking for fields)
table_grant_info	GRANT_INFO of the subject table

Note:

This function does almost the same as fix_fields() for Item_field but is invoked right after trigger definition parsing. Since at this stage we can't say exactly what Field object (corresponding to TABLE::record[0] or TABLE::record[1]) should be bound to this Item, we only find out index of the Field and then select concrete Field object in fix_fields() (by that time Table_trigger_list::old_field/ new_field should point to proper array of Fields). It also binds Item_trigger_field to Table_triggers_list object for table of trigger which uses this item.

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The documentation for this class was generated from the following files:

• item.h
• item.cc