key_spec.h

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/* Copyright (c) 2015, 2023, Oracle and/or its affiliates.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   documentation.  The authors of MySQL hereby grant you an additional
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   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef KEY_SPEC_INCLUDED
#define KEY_SPEC_INCLUDED
 
#include <sys/types.h>
 
#include "lex_string.h"
#include "m_string.h"
#include "my_base.h"
#include "sql/mem_root_array.h"
#include "sql/sql_list.h"
 
class Create_field;
class Item;
class THD;
struct MEM_ROOT;
 
enum keytype {
  KEYTYPE_PRIMARY,
  KEYTYPE_UNIQUE,
  KEYTYPE_MULTIPLE,
  KEYTYPE_FULLTEXT,
  KEYTYPE_SPATIAL,
  KEYTYPE_FOREIGN
};
 
enum fk_option {
  FK_OPTION_UNDEF,
  FK_OPTION_RESTRICT,
  FK_OPTION_CASCADE,
  FK_OPTION_SET_NULL,
  FK_OPTION_NO_ACTION,
  FK_OPTION_DEFAULT
};
 
enum fk_match_opt {
  FK_MATCH_UNDEF,
  FK_MATCH_FULL,
  FK_MATCH_PARTIAL,
  FK_MATCH_SIMPLE
};
 
enum enum_order : int { ORDER_NOT_RELEVANT = 1, ORDER_ASC, ORDER_DESC };
 
class KEY_CREATE_INFO {
 public:
  enum ha_key_alg algorithm = HA_KEY_ALG_SE_SPECIFIC;
  /**
    A flag which indicates that index algorithm was explicitly specified
    by user.
  */
  bool is_algorithm_explicit = false;
  ulong block_size = 0;
  LEX_CSTRING parser_name = {NullS, 0};
  LEX_CSTRING comment = {NullS, 0};
  bool is_visible = true;
 
  KEY_CREATE_INFO() = default;
 
  explicit KEY_CREATE_INFO(bool is_visible_arg) : is_visible(is_visible_arg) {}
 
  LEX_CSTRING m_engine_attribute = EMPTY_CSTR;
  LEX_CSTRING m_secondary_engine_attribute = EMPTY_CSTR;
};
 
extern KEY_CREATE_INFO default_key_create_info;
 
class Key_part_spec {
 public:
  Key_part_spec(Item *expression, enum_order order)
      : m_is_ascending((order == ORDER_DESC) ? false : true),
        m_is_explicit(order != ORDER_NOT_RELEVANT),
        m_field_name(nullptr),
        m_prefix_length(0),
        m_expression(expression),
        m_has_expression(true) {}
 
  Key_part_spec(const char *column_name, Item *expression, enum_order order)
      : m_is_ascending((order == ORDER_DESC) ? false : true),
        m_is_explicit(order != ORDER_NOT_RELEVANT),
        m_field_name(column_name),
        m_prefix_length(0),
        m_expression(expression),
        m_has_expression(true) {}
 
  Key_part_spec(LEX_CSTRING column_name, uint prefix_length, enum_order order)
      : m_is_ascending((order == ORDER_DESC) ? false : true),
        m_is_explicit(order != ORDER_NOT_RELEVANT),
        m_field_name(column_name.str),
        m_prefix_length(prefix_length),
        m_expression(nullptr),
        m_has_expression(false) {}
 
  bool operator==(const Key_part_spec &other) const;
  /**
    Construct a copy of this Key_part_spec. field_name is copied
    by-pointer as it is known to never change. At the same time
    'length' may be reset in mysql_prepare_create_table, and this
    is why we supply it with a copy.
 
    @return If out of memory, 0 is returned and an error is set in
    THD.
  */
  Key_part_spec *clone(MEM_ROOT *mem_root) const {
    return new (mem_root) Key_part_spec(*this);
  }
 
  const char *get_field_name() const { return m_field_name; }
 
  uint get_prefix_length() const { return m_prefix_length; }
 
  Item *get_expression() const {
    assert(has_expression());
    return m_expression;
  }
 
  /**
    @retval true  if this is an ascending index.
    @retval false if this is a descending index.
  */
  bool is_ascending() const { return m_is_ascending; }
 
  /**
    @retval true  if the user explicitly specified the index direction when
                  creating the index.
    @retval false if the user didn't specify the index direction.
  */
  bool is_explicit() const { return m_is_explicit; }
 
  /**
    Resolve the expression that this key part contains. Should only be called
    if has_expression() returns true.
 
    @param thd thread handler.
 
    @retval true if an error occurred.
    @retval false on success.
  */
  bool resolve_expression(THD *thd);
 
  /**
    Set the name and the prefix length of the column this key part references.
    The supplied column name string should have a lifetime equal to or longer
    than this Key_part_spec
 
    @param name the new column that this key part points to.
    @param prefix_length the prefix length of the index, or 0 if no length is
                         specified.
  */
  void set_name_and_prefix_length(const char *name, uint prefix_length);
 
  /**
    @retval true if this index has an expression. In that case, this a
                 functional key part.
    @retval false if this index doesn't have an expression. In that case this
                  key part references a normal column.
  */
  bool has_expression() const { return m_has_expression; }
 
 private:
  /// true <=> ascending, false <=> descending.
  const bool m_is_ascending;
 
  /// true <=> ASC/DESC is explicitly specified, false <=> implicit ASC
  const bool m_is_explicit;
 
  /// The name of the column that this key part points to.
  const char *m_field_name;
 
  /// The prefix length of this index.
  uint m_prefix_length;
 
  /**
    The indexed expression if this is a functional key part. If this key part
    points to a "normal" column, m_expression is nullptr.
  */
  Item *m_expression;
 
  /**
    Whether this key part has an expression or not. If so, this is a functional
    key part.
  */
  bool m_has_expression;
};
 
class Key_spec {
 public:
  const keytype type;
  const KEY_CREATE_INFO key_create_info;
  Mem_root_array<Key_part_spec *> columns;
  LEX_CSTRING name;
  const bool generated;
  /**
    A flag to determine if we will check for duplicate indexes.
    This typically means that the key information was specified
    directly by the user (set by the parser) or a column
    associated with it was dropped.
  */
  const bool check_for_duplicate_indexes;
 
  Key_spec(MEM_ROOT *mem_root, keytype type_par, const LEX_CSTRING &name_arg,
           const KEY_CREATE_INFO *key_info_arg, bool generated_arg,
           bool check_for_duplicate_indexes_arg, List<Key_part_spec> &cols)
      : type(type_par),
        key_create_info(*key_info_arg),
        columns(mem_root),
        name(name_arg),
        generated(generated_arg),
        check_for_duplicate_indexes(check_for_duplicate_indexes_arg) {
    columns.reserve(cols.elements);
    List_iterator<Key_part_spec> it(cols);
    Key_part_spec *column;
    while ((column = it++)) columns.push_back(column);
  }
 
  virtual ~Key_spec() = default;
};
 
class Foreign_key_spec : public Key_spec {
 public:
  const LEX_CSTRING ref_db;
  const LEX_CSTRING orig_ref_db;
  const LEX_CSTRING ref_table;
  const LEX_CSTRING orig_ref_table;
  Mem_root_array<Key_part_spec *> ref_columns;
  const fk_option delete_opt;
  const fk_option update_opt;
  const fk_match_opt match_opt;
  /**
    Indicates whether foreign key name was provided explicitly or
    was generated automatically.
 
    @todo Get rid of this flag once we implement a better way for
          NDB SE to get generated foreign key name from SQL-layer.
    @sa   prepare_foreign_key().
  */
  const bool has_explicit_name;
 
  Foreign_key_spec(MEM_ROOT *mem_root, const LEX_CSTRING &name_arg,
                   List<Key_part_spec> cols, const LEX_CSTRING &ref_db_arg,
                   const LEX_CSTRING &orig_ref_db_arg,
                   const LEX_CSTRING &ref_table_arg,
                   const LEX_CSTRING &orig_ref_table_arg,
                   List<Key_part_spec> *ref_cols, fk_option delete_opt_arg,
                   fk_option update_opt_arg, fk_match_opt match_opt_arg)
      : Key_spec(mem_root, KEYTYPE_FOREIGN, name_arg, &default_key_create_info,
                 false,
                 false,  // We don't check for duplicate FKs.
                 cols),
        ref_db(ref_db_arg),
        orig_ref_db(orig_ref_db_arg),
        ref_table(ref_table_arg),
        orig_ref_table(orig_ref_table_arg),
        ref_columns(mem_root),
        delete_opt(delete_opt_arg),
        update_opt(update_opt_arg),
        match_opt(match_opt_arg),
        has_explicit_name(name_arg.str != nullptr) {
    if (ref_cols) {
      ref_columns.reserve(ref_cols->elements);
      List_iterator<Key_part_spec> it(*ref_cols);
      Key_part_spec *ref_column;
      while ((ref_column = it++)) ref_columns.push_back(ref_column);
    }
  }
 
  /**
    Check if the foreign key name has valid length and its options
    are compatible with columns on which the FK is created.
 
    @param thd                  Thread handle
    @param table_name           Table name (for error reporting)
    @param table_fields         List of columns
 
    @retval false   Key valid
    @retval true    Key invalid
   */
  bool validate(THD *thd, const char *table_name,
                List<Create_field> &table_fields) const;
};
 
/**
  Test if a foreign key (= generated key) is a prefix of the given key
  (ignoring key name, key type and order of columns)
 
  @note This is only used to test if an index for a FOREIGN KEY exists.
  We only compare field names.
 
  @retval false   Generated key is a prefix of other key
  @retval true    Not equal
*/
bool foreign_key_prefix(const Key_spec *a, const Key_spec *b);
 
#endif  // KEY_SPEC_INCLUDED