statement.h

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/* Copyright (c) 2023, 2024, 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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#ifndef RUN_COMMAND_H
#define RUN_COMMAND_H
 
#include <cstddef>
#include <forward_list>
#include <new>
#include <string>
#include <string_view>
 
#include "lex_string.h"
#include "my_alloc.h"
#include "my_inttypes.h"
#include "mysql_time.h"
#include "sql/current_thd.h"
#include "sql/sql_class.h"
#include "sql/sql_cursor.h"
#include "sql/sql_prepare.h"  // Prepared_statement
#include "sql/statement/protocol_local_v2.h"
#include "sql/statement/statement_runnable.h"
#include "utils.h"
 
/**
  There must be one function of this kind in order for the symbols in the
  server's dynamic library to be visible to components.
*/
int dummy_function_to_ensure_we_are_linked_into_the_server();
 
/**
 * @brief
 * Statement_handle is extension of Ed_connection. Some of the
 * limitations in Ed_connection is that,
 * - It does not support reading result metadata
 * - It does not support prepared statement, parameters and cursors.
 *
 * Above limitation leads to implementation of this interface.
 *
 * Statement_handle supports both execution of regular and
 * prepared statement.
 *
 * Note that we can get rid of Ed_connection implementation
 * as we support more functionality with Statement_handle.
 */
class Statement_handle {
 public:
  Statement_handle(THD *thd, const char *query, size_t length);
 
  /**
   * @brief Check if error is reported.
   *
   * @return true of error is reported.
   */
  bool is_error() const { return m_diagnostics_area->is_error(); }
 
  /**
   * @brief Check if error is reported.
   *
   * @return true of error is reported.
   */
  const char *get_last_error() {
    assert(is_error());
    return convert_and_store(&m_warning_mem_root,
                             m_diagnostics_area->message_text(),
                             strlen(m_diagnostics_area->message_text()),
                             system_charset_info, m_expected_charset);
  }
 
  /**
   * @brief Get the last mysql errno.
   *
   * @return unsigned int
   */
  unsigned int get_last_errno() const {
    assert(is_error());
    return m_diagnostics_area->mysql_errno();
  }
 
  /**
   * @brief Get the mysql error state.
   *
   * @return const char*
   */
  const char *get_mysql_state() {
    assert(is_error());
    return convert_and_store(&m_warning_mem_root,
                             m_diagnostics_area->returned_sqlstate(),
                             strlen(m_diagnostics_area->returned_sqlstate()),
                             system_charset_info, m_expected_charset);
  }
 
  /**
   * @brief Get number of warnings generated.
   *
   * @return ulonglong
   */
  ulonglong warning_count() const { return m_warnings_count; }
 
  /**
   * @brief Get list of all warnings.
   *
   * @return Warning*
   */
  Warning *get_warnings();
 
  /**
   * @brief Get the next result sets generated while executing the statement.
   *
   * @return Result_set*
   */
  Result_set *get_result_sets() { return m_result_sets; }
 
  /**
   * @brief Get the current result set object
   *
   * @return Result_set*
   */
  Result_set *get_current_result_set() { return m_current_rset; }
 
  /**
   * @brief Make the next result set the current result set.
   * We do it once we have read the current result set.
   *
   */
  void next_result_set() {
    auto next_rset = m_current_rset->get_next();
    m_current_rset = next_rset;
  }
 
  /**
   * @brief Execute the SQL command.
   * This can be either Regular or Prepared statement.
   *
   * @return true upon failure.
   * @return false upon success.
   */
  virtual bool execute() = 0;
 
  /**
   * @brief Check if we are processing a prepared statement.
   *
   * @return true upon failure.
   * @return false upon success.
   */
  virtual bool is_prepared_statement() = 0;
 
  /**
   * @brief Check if the statement has been executed or prepared
   *
   * @return true upon executed or prepared
   * @return false otherwise
   */
  virtual bool is_executed_or_prepared() = 0;
 
  /**
   * @brief Feel all the result collected so far, from query execution.
   *
   */
  void free_old_result();
 
  /**
   * @brief Get the query string being executed.
   *
   * @return std::string_view
   */
  std::string_view get_query() { return m_query; }
 
  /**
   * @brief Set the capacity in bytes allowed for caching results.
   *
   * @param capacity of the result set
   */
  void set_capacity(size_t capacity) {
    m_protocol.set_result_set_capacity(capacity);
  }
 
  /**
   * @brief Get the capacity in bytes allowed for caching results.
   *
   * @return size_t
   */
  size_t get_capacity() { return m_protocol.get_result_set_capacity(); }
 
  /**
   * @brief Set thd protocol to enable result pass through.
   *
   * @param use_thd_protocol - parameter that decides if THD protocol should be
   * used
   */
  void set_use_thd_protocol(bool use_thd_protocol) {
    m_use_thd_protocol = use_thd_protocol;
  }
 
  /**
   * @brief Check if thd protocol is used.
   *
   * @return true if enabled.
   * @return false if not.
   */
  bool is_using_thd_protocol() const { return m_use_thd_protocol; }
 
  /**
   * @brief Set either Protocol_local_v2 when m_use_thd_protocol is not set or
   *        or classical protocol when m_use_thd_protocol is set to THD.
   */
  void set_thd_protocol();
 
  /**
   * @brief Reset THD protocol.
   */
  void reset_thd_protocol();
 
  /**
   * @brief Set the expected charset
   *
   * @param charset_name Name of the charset
   */
  void set_expected_charset(const char *charset_name) {
    m_expected_charset =
        get_charset_by_csname(charset_name, MY_CS_PRIMARY, MYF(0));
  }
 
  /**
   * @brief Get the expected charset
   *
   * @return const char* the expected charset name
   */
  const char *get_expected_charset() {
    if (m_expected_charset == nullptr) return nullptr;
    return m_expected_charset->csname;
  }
 
  /**
   * @brief Get the num rows per fetch.
   *
   * @return size_t
   */
  size_t get_num_rows_per_fetch() { return m_num_rows_per_fetch; }
 
  /**
   * @brief Set the num of rows to be retrieved per fetch.
   *
   * @param num_rows_per_fetch number of rows per fetch
   */
  void set_num_rows_per_fetch(size_t num_rows_per_fetch) {
    m_num_rows_per_fetch = num_rows_per_fetch;
  }
 
  /**
   * @brief Destroy the Statement_handle object
   *
   */
  virtual ~Statement_handle() { free_old_result(); }
 
 protected:
  /**
   * @brief Send statement execution status after execute().
   */
  void send_statement_status();
 
 protected:
  // The query being executed.
  std::string m_query;
 
  // Details about error or warning occured.
  MEM_ROOT m_warning_mem_root;
  Warning *m_warnings;
  ulonglong m_warnings_count = 0;
  Diagnostics_area *m_diagnostics_area;
 
  // The thread executing the statement.
  THD *m_thd;
 
  // List of all results generated by the query.
  Result_set *m_result_sets;
 
  // The last result generated by the guery.
  Result_set *m_current_rset;
 
  // Do not intercept the results in the protocol, but pass it to
  // THD* protocol. E.g., if this is set to 'false', the results are
  // captured into Protocol_result_v2, else it goes to THD->get_protocol()
  bool m_use_thd_protocol = false;
 
  // Max rows to read per fetch() call.
  size_t m_num_rows_per_fetch = 1;
 
  CHARSET_INFO *m_expected_charset;
 
  // Collect result set from single statement.
  void add_result_set(Result_set *result_set);
 
  // Set result set from prepared statement with cursor.
  // This is called at the end of fetch().
  void set_result_set(Result_set *result_set);
 
  /**
   * @brief Copy the warnings generated for the query from the
   * diagnostics area
   */
  void copy_warnings();
 
  // Protocol that intercepts all the rows from query executed.
  Protocol_local_v2 m_protocol;
  friend class Protocol_local_v2;
 
  // Protocol used by THD before switching.
  Protocol *m_saved_protocol{nullptr};
 
  // No copies.
  Statement_handle(const Statement_handle &) = delete;
  // No move.
  Statement_handle(Statement_handle &&) = delete;
  // No self assignment.
  Statement_handle &operator=(const Statement_handle &) = delete;
  // No move.
  Statement_handle &operator=(Statement_handle &&) = delete;
};
 
/**
 * @brief Regular_statement_handle enables execution of all SQL statements
 * except for prepared statements.
 */
class Regular_statement_handle : public Statement_handle {
 public:
  Regular_statement_handle(THD *thd, const char *query, uint length)
      : Statement_handle(thd, query, length) {}
 
  /**
   * @brief Execute a regular statement.
   *
   * @return true if statement fails.
   * @return false if statement succeeds.
   */
  bool execute() override;
 
  /**
   * @brief Convey that this is regular statement.
   *
   * @return Always returns 'false'
   */
  bool is_prepared_statement() override { return false; }
 
  /**
   * @brief Check if the statement has been executed
   *
   * @return true if executed
   * @return false otherwise
   */
  bool is_executed_or_prepared() override { return m_is_executed; }
 
 private:
  // Flag to show whether statement has been executed. Change to true after
  // execute is called
  bool m_is_executed = false;
 
  // Used by execute() above.
  bool execute(Server_runnable *server_runnable);
};
 
/**
 * @brief Prepared_statement_handle enables support for prepared
 * statement execution. Supports parameters and cursors.
 */
class Prepared_statement_handle : public Statement_handle {
 public:
  Prepared_statement_handle(THD *thd, const char *query, uint length)
      : Statement_handle(thd, query, length),
        m_parameter_mem_root(key_memory_prepared_statement_main_mem_root,
                             thd->variables.query_alloc_block_size) {}
 
  /**
   * @brief Prepares the statement using m_query.
   *
   * If the statement is already in executing mode, close the cursor
   * deallocate the previous statement and start preparing new statement
   * using m_query.
   *
   * @return true if fails.
   * @return false if succeeds.
   */
  bool prepare();
 
  /**
   * @brief Set the parameter value in a prepared statement.
   *
   * @param idx            Index of '?' in prepared statement.
   * @param is_null        Set parameter to NULL value.
   * @param type           Set the parameters field type.
   * @param is_unsigned    Mark parameter as unsigned.
   * @param data           Pointer to buffer containing the value.
   * @param data_length    Length of buffer 'data'
   * @param name           Name of parameter (mostly unused)
   * @param name_length    Length of 'name'
   *
   * @return true if fails.
   * @return false if succeeds.
   */
  bool set_parameter(uint idx, bool is_null, enum_field_types type,
                     bool is_unsigned, const void *data,
                     unsigned long data_length, const char *name,
                     unsigned long name_length);
 
  /**
   * @brief Get the parameter object
   *
   * @param index of the parameter
   * @return Item_param*
   */
  Item_param *get_parameter(size_t index);
 
  /**
   * @brief Execute the statement that is prepared.
   *
   * If a statement is not yet prepared, we fail.
   *
   * If a statement was already in EXECUTED state, we close the cursor
   * and execute the statement again.
   *
   * @return true
   * @return false
   */
  bool execute() override;
 
  /**
   * @brief Fetch rows from statement using cursor.
   *
   * Not all statement uses cursor. Check is_cursor_open() and
   * then invoke this call.
   *
   * Attempt to call fetch rows without preparing or executing the
   * statement will cause failure.
   *
   * Attempt to call fetch() without cursor in use, will cause failure.
   *
   * @return true
   * @return false
   */
  bool fetch();
 
  /**
   * @brief Check if the statement uses cursor and it is open.
   *
   * If the API is called without preparing the statement will
   * result in 'false'
   *
   * @return true if cursor is in use
   * @return false if cursor not in use.
   */
  bool is_cursor_open() {
    if (!m_stmt) return false;
    return m_stmt->m_cursor && m_stmt->m_cursor->is_open();
  }
 
  /**
   * @brief Check if the statement uses cursor.
   *
   * If the API is called without executing the statement
   * will result in 'false'
   *
   * @return true if statement uses cursor.
   * @return false if statement does not uses cursor.
   */
  bool uses_cursor() {
    if (!m_stmt || m_stmt->m_arena.get_state() != Query_arena::STMT_EXECUTED)
      return false;
    return m_stmt->m_cursor != nullptr;
  }
 
  /**
   * @brief Reset the statement parameters and cursors.
   *
   * Invoking this API will close the cursor in use.
   * This is invoked generally before executing
   * the statement for the second time, after prepare.
   *
   * @return true
   * @return false
   */
  bool reset();
 
  /**
   * @brief Close the statement that is prepared.
   *
   * @return true
   * @return false
   */
  bool close();
 
  /**
   * @brief Get number of parameters used in the statement.
   *
   * This should be called after preparing a statement.
   *
   * @return uint
   */
  uint get_param_count() { return m_stmt ? m_stmt->m_param_count : 0; }
 
  /**
   * @brief Convey that this is prepared statement.
   *
   * @return Always returns true
   */
  bool is_prepared_statement() override { return true; }
 
  /**
   * @brief Check if the statement has been executed or prepared
   *
   * @return true if executed or prepared
   * @return false otherwise
   */
  bool is_executed_or_prepared() override {
    return m_stmt != nullptr &&
           m_stmt->m_arena.get_state() > Query_arena::STMT_INITIALIZED;
  }
 
  /**
   * @brief Virtual destroy for Prepared_statement_handle object
   *
   */
  virtual ~Prepared_statement_handle() override { internal_close(); }
 
 private:
  /**
   * @brief This is a wrapper function used to execute
   * and operation on Prepared_statement. This takes case of using
   * relevant protocol, diagnostic area, backup the current query arena
   * before executing the prepared statement operation.
   *
   * @tparam Function type of function to run
   * @param exec_func function to run
   * @return true
   * @return false
   */
  template <typename Function>
  bool run(Function exec_func);
 
  // See prepare()
  bool internal_prepare();
 
  // See execute()
  bool internal_execute();
 
  // See fetch()
  bool internal_fetch();
 
  // See reset()
  bool internal_reset();
 
  /**
   * @brief Reset the statement parameters and cursors.
   *
   * @param invalidate_params   When set to true parameters are invalidated.
   *
   * @return true on failure.
   * @return false on execute.
   */
 
  bool internal_reset(bool invalidate_params);
 
  // See close()
  bool internal_close();
 
  /**
   * @brief Method to enable cursor.
   *
   * @return true if cursor can be used for a statement.
   * @return false if cursor can not be used for a statement.
   */
  bool enable_cursor();
 
  /**
   * @brief Create a parameter buffers
   *
   * @return true on failure
   * @return false on success
   */
  bool create_parameter_buffers();
 
  // The prepared statement implementation.
  Prepared_statement *m_stmt{nullptr};
 
  // Parameters values.
  PS_PARAM *m_parameters{nullptr};
 
  /*
    Store the parameter and parameter values in a separate mem_root.
    These can be even stored in m_stmt's mem_root. But reprepare() would
    free up the memory used by the prepared statement. Hence, using separate
    mem_root.
  */
  MEM_ROOT m_parameter_mem_root;
 
  /*
    Size of each parameter buffer allocated in mem_root.
    We re-use the same buffer, if the parameter value size fit
    within this max.
  */
  ulong *m_parameter_buffer_max{nullptr};
 
  /*
    Denotes if new parameters were set.
    This is set 'true' for the first time. It is set to 'false' upon
    re-execute without rebinding any parameters.
  */
  bool m_bound_new_parameter_types{true};
};
 
#endif