12.9 Union Engine


  • constructor just store pointer to st_select_lex_union (SELECT_LEX_UNION).

  • prepare() call st_select_lex_unit::prepare.

  • fix_length_and_dec() prepare cache and receive type and parameters (maximum of length) of returning items (called only by Item_singlerow_subselect).

  • exec() call st_select_lex_unit::exec(). st_select_lex_unit::exec() can drop 'assigned' flag of Item_subselect if st_select_lex_unit::item is not 0.

Download this Manual
EPUB - 0.8Mb
User Comments
Sign Up Login You must be logged in to post a comment.