protocol_local_v2.h

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/* Copyright (c) 2023, 2024, Oracle and/or its affiliates.
 
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it under the terms of the GNU General Public License, version 2.0,
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef PROTOCOL_LOCAL_V2_H
#define PROTOCOL_LOCAL_V2_H
 
#include <variant>
 
#include "my_sys.h"
#include "mysqld_error.h"
#include "sql-common/my_decimal.h"
#include "sql/field.h"
#include "sql/protocol.h"
#include "sql/sql_class.h"
 
class Statement_handle;
 
/**
 * @brief A structure to store a decimal value together with its precision and
 * number of decimals
 * TODO: HCS-10094 - Do we really need this struct?
 */
struct decimal {
  my_decimal decimal;
  uint prec;
  uint dec;
};
 
/**
 * @brief A type to store the value of a Column which can be one of all the
 * types that are supported by the Protocol_local_v2. Variant of pointers is
 * used instead of variant of values as the values are stored and managed by
 * mem_root. The pointers point to these values on mem_root.
 */
using value_t = std::variant<std::monostate, int64_t *, uint64_t *, double *,
                             MYSQL_TIME *, LEX_CSTRING, decimal *>;
 
/**
 * @brief The metadata of a Column
 *        Need to keep in-sync with Send_field class.
 *
 */
struct Column_metadata {
  const char *database_name;
  const char *table_name, *original_table_name;
  const char *column_name, *original_col_name;
  ulong length;
  uint charsetnr, flags, decimals;
  enum_field_types type;
};
 
/**
 * @brief A structure to store all information about a warning/error
 *
 */
struct Warning {
  Warning(const uint32 level, const uint32_t code, LEX_CSTRING message)
      : m_level(level), m_code(code), m_message(message) {}
 
  uint32_t m_level;
  uint32_t m_code;
  LEX_CSTRING m_message;
};
 
/**
 * @brief A row of result or a row of metadata
 *        A row is a collection of Column values or Column metadata.
 *
 * @tparam T type of the result set
 */
template <typename T>
class Row {
 private:
  T *m_column_array;
  size_t m_column_count; /* TODO: HCS-9478 change to point to metadata */
 
 public:
  const T &operator[](const unsigned int column_index) const {
    return *get_column(column_index);
  }
  T *get_column(const unsigned int column_index) const {
    assert(column_index < size());
    return m_column_array + column_index;
  }
  size_t size() const { return m_column_count; }
 
  Row(T *column_array_arg, size_t column_count_arg)
      : m_column_array(column_array_arg), m_column_count(column_count_arg) {}
 
  T *get_column_array() { return m_column_array; }
};
 
/**
 * @brief This class is used to limit the bytes collected in Result_set.
 * this is required to avoid exhausting MEM_ROOT, when fetch large set of rows.
 */
class Result_set_capacity {
 private:
  // Max capacity in bytes
  static constexpr auto MAX_CAPACITY{500};
 
  // Configured capacity in bytes
  uint64_t m_configured_capacity{MAX_CAPACITY};
 
  uint64_t m_current_capacity{0};
 
 public:
  // Add bytes to capacity.
  // Note: since add_bytes is called after calling new in the store_ functions,
  // the bytes have been allocated but they might not be shown to the end-users.
  // See add_row_to_result_set
  void add_bytes(uint64_t amend) {
    m_current_capacity += amend;
 
    if (!has_capacity()) my_error(ER_RESULT_SIZE_LIMIT_EXCEEDED, MYF(0));
  }
 
  // Check if the result set can have more bytes.
  bool has_capacity() { return m_current_capacity < m_configured_capacity; }
 
  // Reset the limit. When we are done fetching all rows.
  void reset() { m_current_capacity = 0; }
 
  void set_capacity(uint64_t cap) { m_configured_capacity = cap; }
 
  uint64_t get_capacity() { return m_configured_capacity; }
};
 
/**
 * @brief A result set contains the result of a query. It is a collection of
 *        Rows and its metadata
 *
 */
class Result_set {
 private:
  // Metadata
  Row<Column_metadata> *m_fields{nullptr};
  size_t m_column_count{0};
 
  // Rows
  List<Row<value_t>> *m_rows{nullptr};
 
  // Row iterator
  List_iterator_fast<Row<value_t>> m_row_iterator;
 
  // Next result set
  Result_set *m_next{nullptr};
 
  ulonglong m_affected_row{0};
  ulonglong m_last_insert_id{0};
 
  // Avoid copying the object.
  Result_set(const Result_set &) = delete;
  Result_set &operator=(Result_set &) = delete;
  Result_set(const Result_set &&) = delete;
  Result_set &operator=(Result_set &&) = delete;
 
 public:
  Result_set();
 
  Result_set(List<Row<value_t>> *rows_arg, Row<Column_metadata> *fields,
             size_t column_count, ulonglong affected_rows,
             ulonglong last_insert_id);
 
  ~Result_set() = default;
 
  /**
   * @brief Get the next row
   *
   * @return void*
   */
  Row<value_t> *get_next_row() {
    return static_cast<Row<value_t> *>(m_row_iterator.next());
  }
  /**
   * @brief Check if the iterator is at the last row
   *
   * @return true
   * @return false
   */
  bool is_last_row() { return m_row_iterator.is_last(); }
 
  /**
   * @brief Get the num affected row count
   *
   * @return uint
   */
  ulonglong get_num_affected_rows() const { return m_affected_row; }
 
  /**
   * @brief Get the last insert id
   *
   * @return uint
   */
  ulonglong get_last_insert_id() const { return m_last_insert_id; }
 
  /**
   * @brief Get the list of rows from result set
   *
   * @return List<Row<value_t>>*
   */
  List<Row<value_t>> *get_rows() { return m_rows; }
 
  /**
   * @brief Get reference for rows in results set.
   *
   * @return List<Row<value_t>> &
   */
  operator List<Row<value_t>> &() { return *m_rows; }
 
  /**
   * @brief Get number for rows in result set.
   *
   * @return unsigned int
   */
  unsigned int size() const { return m_rows->elements; }
 
  /**
   * @brief Get the field metadata
   *
   * @return Row<Column_metadata>*
   */
  Row<Column_metadata> *get_fields() { return m_fields; }
 
  /**
   * @brief Get the field count in result set.
   *
   * @return size_t
   */
  size_t get_field_count() const { return m_column_count; }
 
  /**
   * @brief Custom memory allocation for Result set object.
   *
   * @param size size of the memory
   * @param mem_root mem root object pointer
   * @return void*
   */
  static void *operator new(size_t size, MEM_ROOT *mem_root,
                            const std::nothrow_t & = std::nothrow) noexcept {
    return mem_root->Alloc(size);
  }
 
  static void operator delete(void *) noexcept {}
 
  static void operator delete(void *, MEM_ROOT *,
                              const std::nothrow_t &) noexcept {
    /* purecov: inspected */
  }
 
  /**
   * @brief Check if we have more than one result set.
   *
   * @return true
   * @return false
   */
  bool has_next() { return m_next != nullptr; }
 
  /**
   * @brief Get the next result set object
   *
   * @return Result_set*
   */
  Result_set *get_next() { return m_next; }
 
  /**
   * @brief Set the current result set pointer.
   * Generally used when traversing through all result set.
   *
   * @param ptr pointer to result set
   */
  void set_next(Result_set *ptr) { m_next = ptr; }
 
  // TODO: HCS-9478 remove this method after the hcs is resolved
  /**
   * @brief Update the members of result set
   *
   */
  void update(List<Row<value_t>> *rows_arg, Row<Column_metadata> *fields,
              size_t column_count, ulonglong affected_rows,
              ulonglong last_insert_id) {
    m_rows = rows_arg;
    m_row_iterator.init(*m_rows);
    m_fields = fields;
    m_column_count = column_count;
    m_affected_row = affected_rows;
    m_last_insert_id = last_insert_id;
  }
};
 
/**
 * @brief This is extention of Protocol_local. We support reading field
 * metadata and field data attributes.
 */
class Protocol_local_v2 final : public Protocol {
 private:
  bool store_string(const char *str, size_t length, const CHARSET_INFO *src_cs,
                    const CHARSET_INFO *dst_cs);
  bool store_longlong(longlong value);
  bool store_floating_type(double value);
  bool store_temporal(const MYSQL_TIME &time);
  void add_row_to_result_set();
 
  Statement_handle *m_execute_statement;
 
  MEM_ROOT m_result_set_mem_root;
 
  // Memory for following data members are allocated in above MEM_ROOT.
  Result_set *m_result_set = nullptr;
 
  // TODO: HCS-9478: These are duplicate members as similar as in Result_set
  // class. we can probably use object of Result_set here, instead.
  List<Row<value_t>> *m_data_rows;
  Row<Column_metadata> *m_fields;
 
  value_t *m_current_row;
  value_t *m_current_column;
 
  Column_metadata *m_metadata_row;
  Column_metadata *m_current_metadata_column;
 
  // End of MEM_ROOT members.
 
  // Whether we are receiving metadata or data
  bool m_send_metadata;
  size_t m_column_count;
 
  THD *m_thd;
 
  // Max rows in resultset
  uint m_current_row_index = 0;
 
  Result_set_capacity m_result_set_capacity;
 
  template <typename T, typename V>
  bool allocate_type(V *value);
 
 protected:
  bool store_null() override;
  bool store_tiny(longlong from, uint32) override;
  bool store_short(longlong from, uint32) override;
  bool store_long(longlong from, uint32) override;
  bool store_longlong(longlong from, bool unsigned_flag, uint32) override;
  bool store_decimal(const my_decimal *, uint, uint) override;
  bool store_string(const char *from, size_t length,
                    const CHARSET_INFO *cs) override;
  bool store_datetime(const MYSQL_TIME &time, uint precision) override;
  bool store_date(const MYSQL_TIME &time) override;
  bool store_time(const MYSQL_TIME &time, uint precision) override;
  bool store_float(float value, uint32 decimals, uint32 zerofill) override;
  bool store_double(double value, uint32 decimals, uint32 zerofill) override;
  bool store_field(const Field *field) override;
 
  enum enum_protocol_type type() const override { return PROTOCOL_LOCAL; }
  enum enum_vio_type connection_type() const override {
    return VIO_TYPE_LOCAL; /* purecov: inspected */
  }
 
  bool send_ok(uint server_status, uint statement_warn_count,
               ulonglong affected_rows, ulonglong last_insert_id,
               const char *message) override;
 
  bool send_eof(uint server_status, uint statement_warn_count) override;
  bool send_error(uint sql_errno, const char *err_msg,
                  const char *sqlstate) override;
 
  uint get_current_column_number() {
    if (!m_current_column) return 0;
    assert(m_current_row);
    return m_current_column - m_current_row;
  }
 
 public:
  Protocol_local_v2(THD *thd, Statement_handle *execute_statement);
  ~Protocol_local_v2() override { m_result_set_mem_root.Clear(); }
 
  int read_packet() override;
 
  int get_command(COM_DATA *, enum_server_command *) override {
    return -1; /* purecov: inspected */
  }
  ulong get_client_capabilities() override;
  bool has_client_capability(unsigned long client_capability) override;
  void end_partial_result_set() override;
  int shutdown(bool server_shutdown = false) override;
  bool connection_alive() const override;
  void start_row() override;
  bool end_row() override;
  void abort_row() override {}
  uint get_rw_status() override;
  bool get_compression() override;
 
  char *get_compression_algorithm() override;
  uint get_compression_level() override;
 
  bool start_result_metadata(uint num_cols, uint flags,
                             const CHARSET_INFO *resultcs) override;
  bool end_result_metadata() override;
  bool send_field_metadata(Send_field *field,
                           const CHARSET_INFO *charset) override;
  bool flush() override { return true; /* purecov: inspected */ }
  bool send_parameters(List<Item_param> *, bool) override { return false; }
  bool store_ps_status(ulong, uint, uint, ulong) override {
    return false; /* purecov: inspected */
  }
 
  /**
   * @brief Set the capacity in bytes allowed for caching results.
   *
   * @param capacity capacity of the result set
   */
  void set_result_set_capacity(size_t capacity) {
    m_result_set_capacity.set_capacity(capacity);
  }
 
  /**
   * @brief Get the capacity in bytes allowed for caching results.
   */
  size_t get_result_set_capacity() {
    return m_result_set_capacity.get_capacity();
  }
 
  /**
   * @brief Clear MEM_ROOT and related members.
   *
   */
  void clear_resultset_mem_root();
};
 
#endif