Function mysql_register_view

sql/sql_view.cc:993–1281

*/

static int mysql_register_view(THD *thd, DDL_LOG_STATE *ddl_log_state,
                               TABLE_LIST *view, enum_view_create_mode mode,
                               char *backup_file_name)
{
  LEX *lex= thd->lex;

  /*
    Ensure character set number != 17 (character set = filename) and mbminlen=1
    because these character sets are not parser friendly, which can give weird
    sequence in .frm file of view and later give parsing error.
  */
  DBUG_ASSERT(thd->charset()->mbminlen == 1 && thd->charset()->number != 17);

  /*
    View definition query -- a SELECT statement that fully defines view. It
    is generated from the Item-tree built from the original (specified by
    the user) query. The idea is that generated query should eliminate all
    ambiguities.
    Item::print() virtual operation is used to generate view definition
    query.

    The INFORMATION_SCHEMA query is a SQL statement describing a
    view as shown in the INFORMATION_SCHEMA database. It is the 'view
    definition query' with text literals converted to UTF8 and without
    character set introducers.

    For example:
      Let's suppose we have:
        CREATE TABLE t1(a INT, b INT);
      User specified query:
        CREATE VIEW v1(x, y) AS SELECT * FROM t1;
      Generated query:
        SELECT a AS x, b AS y FROM t1;
      INFORMATION_SCHEMA query:
        SELECT a AS x, b AS y FROM t1;

    View definition query is stored in the client character set.
  */
  constexpr const size_t BUFF_4K= 4096;
  StringBuffer<BUFF_4K> view_query(thd->charset());
  StringBuffer<BUFF_4K> is_query(system_charset_info); // information_schema

  char md5[MD5_BUFF_LENGTH];
  bool can_be_merged;
  char dir_buff[FN_REFLEN + 1], path_buff[FN_REFLEN + 1];
  LEX_CSTRING dir, file, path;
  int error= 0;
  bool old_view_exists= 0;
  DBUG_ENTER("mysql_register_view");

  /* Generate view definition and IS queries. */
  view_query.length(0);
  is_query.length(0);
  backup_file_name[0]= 0;
  {
    Sql_mode_save_for_frm_handling sql_mode_save(thd);

    lex->unit.print(&view_query, enum_query_type(QT_FOR_FRM |