system_view_definition_impl.h

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#ifndef DD_SYSTEM_VIEWS__SYSTEM_VIEW_DEFINITION_IMPL_INCLUDED
#define DD_SYSTEM_VIEWS__SYSTEM_VIEW_DEFINITION_IMPL_INCLUDED

#include <map>
#include <memory>
#include <vector>

#include "sql/dd/string_type.h"                   // dd::String_type
#include "sql/dd/types/system_view_definition.h"  // dd::System_view_definition
#include "sql/mysqld.h"                           // lower_case_table_names

namespace dd {
namespace system_views {

class System_view_definition_impl : public System_view_definition {
 public:
  /**
    Get view name.

    @return name of the view.
  */
  virtual const String_type &view_name() const { return m_view_name; }

  /**
    Set view name.
  */
  virtual void set_view_name(const String_type &name) { m_view_name = name; }

  /**
    Get collation clause to append to view definition for some
    view columns based on lower_case_table_names.

    @return Empty string if lctn=0, other wise " COLLATE utf8mb3_tolower_ci".
  */
  static const String_type fs_name_collation() {
    if (lower_case_table_names != 0) return " COLLATE utf8mb3_tolower_ci";
    return "";
  }

  String_type build_ddl_create_view() const override = 0;

 private:
  // Name of I_S system view;
  String_type m_view_name;
};

class System_view_select_definition_impl : public System_view_definition_impl {
 public:
  /**
    Add a field definition for the SELECT projection.
    This function can be called more than once. The call will add a new
    projection to the SELECT command.

    @param field_number  Ordinal position of field in the projection list.
    @param field_name    Field name used for the SELECT's projection.
    @param field_definition Expression representing the projection.
    @param add_quotes    If true, output single quotes around the
                         field_definition.
  */
  virtual void add_field(int field_number, const String_type &field_name,
                         const String_type &field_definition,
                         bool add_quotes = false) {
    // Make sure the field_number and field_name are not added twise.
    assert(m_field_numbers.find(field_name) == m_field_numbers.end() &&
           m_field_definitions.find(field_number) == m_field_definitions.end());

    // Store the field number.
    m_field_numbers[field_name] = field_number;

    // Store the field definition expression.
    Stringstream_type ss;
    if (field_name == "*") {
      ss << " * ";
    } else {
      if (add_quotes) {
        assert(field_definition.find('\'') == String_type::npos);
        ss << '\'' << field_definition << '\'';
      } else
        ss << field_definition;

      ss << " AS " << field_name;
    }

    m_field_definitions[field_number] = ss.str();
  }

  /**
    Add FROM clause for the SELECT.
    This function can be called more than once. The clause will be appended to
    the previous FROM clause string.

    @param from  String representing the FROM clause.
  */
  virtual void add_from(const String_type &from) {
    m_from_clauses.push_back(from);
  }

  /**
    Add WHERE clause for the SELECT.
    This function can be called more than once. The clause will be appended to
    the previous WHERE clause string.

    @param where  String representing the WHERE clause.
  */
  virtual void add_where(const String_type &where) {
    m_where_clauses.push_back(where);
  }

  /**
    Add CTE expression before SELECT.

    @param cte  String representing the CTE expression.
  */
  virtual void add_cte_expression(const String_type &cte) {
    m_cte_expression = cte;
  }

  /**
    Indicates that we should add DISTINCT clause to SELECT.
  */
  virtual void add_distinct() { m_is_distinct = true; }

  /**
    Indicates selection of all field (SELECT '*').
  */
  virtual void add_star() { m_add_star = true; }
  /**
    Get the field ordinal position number for the given field name.

    @param field_name  Column name for which the field number is returned.

    @return Integer representing position of column in projection list.
  */
  virtual int field_number(const String_type &field_name) const {
    assert(m_field_numbers.find(field_name) != m_field_numbers.end());
    return m_field_numbers.find(field_name)->second;
  }

  /**
    Build the SELECT query that is used in the CREATE VIEW command.

    @return The SELECT query string.
  */
  String_type build_select_query() const {
    Stringstream_type ss;

    if (!m_cte_expression.empty()) ss << m_cte_expression << "\n ";

    // Make SELECT [DISTINCT]
    ss << "SELECT " << (m_is_distinct ? "DISTINCT \n" : "\n");

    if (!m_add_star) {
      // Output view column definitions
      for (Field_definitions::const_iterator field =
               m_field_definitions.begin();
           field != m_field_definitions.end(); ++field) {
        if (field != m_field_definitions.begin()) ss << ",\n";
        ss << "  " << field->second;
      }
    } else
      ss << "*";

    // Output FROM clauses
    for (From_clauses::const_iterator from = m_from_clauses.begin();
         from != m_from_clauses.end(); ++from) {
      if (from == m_from_clauses.begin()) ss << " FROM ";

      ss << "\n  " << *from;
    }

    // Output WHERE clauses
    for (Where_clauses::const_iterator where = m_where_clauses.begin();
         where != m_where_clauses.end(); ++where) {
      if (where == m_where_clauses.begin()) ss << " WHERE ";

      ss << "\n  " << *where;
    }

    ss << "\n";

    return ss.str();
  }

  String_type build_ddl_create_view() const override {
    Stringstream_type ss;
    ss << "CREATE OR REPLACE DEFINER=`mysql.infoschema`@`localhost` VIEW "
       << "information_schema." << view_name() << " AS " + build_select_query();

    return ss.str();
  }

 private:
  // Map of field_names and the ordinal position in SELECT projection.
  typedef std::map<String_type, int> Field_numbers;

  // Map of field ordinal position and their view column definition.
  typedef std::map<int, String_type> Field_definitions;

  // List of FROM clause definition in the SELECT
  typedef std::vector<String_type> From_clauses;

  // List of WHERE clause definition in the SELECT
  typedef std::vector<String_type> Where_clauses;

  Field_numbers m_field_numbers;
  Field_definitions m_field_definitions;
  From_clauses m_from_clauses;
  Where_clauses m_where_clauses;
  dd::String_type m_cte_expression;
  bool m_is_distinct{false};
  bool m_add_star{false};
};

// This class is unused and kept here for future use.
class System_view_union_definition_impl : public System_view_definition_impl {
 public:
  /**
    Get the object for a SELECT definition to be used in the UNION.

    @return The System_view_select_definition_impl&.
  */
  System_view_select_definition_impl &get_query_block() {
    m_selects.push_back(
        Select_definition(new System_view_select_definition_impl));
    return *(m_selects.back().get());
  }

  String_type build_ddl_create_view() const override {
    Stringstream_type ss;
    bool first_query_block = true;
    // Union definition must have minimum two SELECTs.
    assert(m_selects.size() >= 2);

    for (auto &select : m_selects) {
      if (first_query_block) {
        ss << "CREATE OR REPLACE DEFINER=`mysql.infoschema`@`localhost` VIEW "
           << "information_schema." << view_name() << " AS "
           << "(" << select->build_select_query() << ")";
        first_query_block = false;
      } else {
        ss << " UNION "
           << "(" << select->build_select_query() << ")";
      }
    }

    return ss.str();
  }

 private:
  using Select_definition = std::unique_ptr<System_view_select_definition_impl>;

  // Member holds SELECT's used for the UNION
  std::vector<Select_definition> m_selects;
};

}  // namespace system_views
}  // namespace dd

#endif  // DD_SYSTEM_VIEWS__SYSTEM_VIEW_DEFINITION_IMPL_INCLUDED