temp_table_param.h

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#ifndef TEMP_TABLE_PARAM_INCLUDED
#define TEMP_TABLE_PARAM_INCLUDED

#include <vector>

#include "my_base.h"
#include "sql/mem_root_array.h"
#include "sql/sql_list.h"
#include "sql/thr_malloc.h"
#include "sql/window.h"

class KEY;
class Copy_field;
class Item;
class Window;

template <typename T>
using Memroot_vector = std::vector<T, Memroot_allocator<T>>;

/**
   Helper class for copy_funcs(); represents an Item to copy from table to
   next tmp table.
*/
class Func_ptr {
 public:
  explicit Func_ptr(Item *f) : m_func(f) {}
  Item *func() const { return m_func; }
  void set_override_result_field(Field *f) { m_override_result_field = f; }
  Field *override_result_field() const { return m_override_result_field; }

 private:
  Item *m_func;

  /// If not nullptr, copy_funcs() will save the result of m_func here instead
  /// of in m_func's usual designated result field.
  Field *m_override_result_field = nullptr;
};

/// Used by copy_funcs()
typedef Mem_root_array<Func_ptr> Func_ptr_array;

/**
  Object containing parameters used when creating and using temporary
  tables. Temporary tables created with the help of this object are
  used only internally by the query execution engine.
*/

class Temp_table_param {
 public:
  /**
    Used to store the values of grouped non-column-reference expressions in
    between groups, so they can be retreived when the group changes.

    @see setup_copy_fields
    @see copy_fields
  */
  Memroot_vector<Item_copy *> grouped_expressions;
  Memroot_vector<Copy_field> copy_fields;

  uchar *group_buff;
  Func_ptr_array *items_to_copy; /* Fields in tmp table */

  /**
    After temporary table creation, points to an index on the table
    created depending on the purpose of the table - grouping,
    duplicate elimination, etc. There is at most one such index.
  */
  KEY *keyinfo;
  ha_rows end_write_records;
  /**
    Number of normal fields in the query, including those referred to
    from aggregate functions. Hence, "SELECT `field1`,
    SUM(`field2`) from t1" sets this counter to 2.

    @see count_field_types
  */
  uint field_count;
  /**
    Number of fields in the query that have functions. Includes both
    aggregate functions (e.g., SUM) and non-aggregates (e.g., RAND)
    and windowing functions.
    Also counts functions referred to from windowing or aggregate functions,
    i.e., "SELECT SUM(RAND())" sets this counter to 2.

    @see count_field_types
  */
  uint func_count;
  /**
    Number of fields in the query that have aggregate functions. Note
    that the optimizer may choose to optimize away these fields by
    replacing them with constants, in which case sum_func_count will
    need to be updated.

    @see optimize_aggregated_query, count_field_types
  */
  uint sum_func_count;
  uint hidden_field_count;
  uint group_parts, group_length, group_null_parts;
  uint quick_group;
  /**
    Number of outer_sum_funcs i.e the number of set functions that are
    aggregated in a query block outer to this subquery.

    @see count_field_types
  */
  uint outer_sum_func_count;
  /**
    Enabled when we have atleast one outer_sum_func. Needed when used
    along with distinct.

    @see create_tmp_table
  */
  bool using_outer_summary_function;
  CHARSET_INFO *table_charset;
  bool schema_table;
  /*
    True if GROUP BY and its aggregate functions are already computed
    by a table access method (e.g. by loose index scan). In this case
    query execution should not perform aggregation and should treat
    aggregate functions as normal functions.
  */
  bool precomputed_group_by;
  bool force_copy_fields;
  /**
    true <=> don't actually create table handler when creating the result
    table. This allows range optimizer to add indexes later.
    Used for materialized derived tables/views.
    @see TABLE_LIST::update_derived_keys.
  */
  bool skip_create_table;
  /*
    If true, create_tmp_field called from create_tmp_table will convert
    all BIT fields to 64-bit longs. This is a workaround the limitation
    that MEMORY tables cannot index BIT columns.
  */
  bool bit_fields_as_long;

  /// Whether the UNIQUE index can be promoted to PK
  bool can_use_pk_for_unique;

  /// (Last) window's tmp file step can be skipped
  bool m_window_short_circuit;

  /// This tmp table is used for a window's frame buffer
  bool m_window_frame_buffer{false};

  /// If this is the out table of a window: the said window
  Window *m_window;

  Temp_table_param(MEM_ROOT *mem_root = *THR_MALLOC)
      : grouped_expressions(Memroot_allocator<Item_copy *>(mem_root)),
        copy_fields(Memroot_allocator<Copy_field>(mem_root)),
        group_buff(nullptr),
        items_to_copy(nullptr),
        keyinfo(NULL),
        end_write_records(0),
        field_count(0),
        func_count(0),
        sum_func_count(0),
        hidden_field_count(0),
        group_parts(0),
        group_length(0),
        group_null_parts(0),
        quick_group(1),
        outer_sum_func_count(0),
        using_outer_summary_function(false),
        table_charset(NULL),
        schema_table(false),
        precomputed_group_by(false),
        force_copy_fields(false),
        skip_create_table(false),
        bit_fields_as_long(false),
        can_use_pk_for_unique(true),
        m_window_short_circuit(false),
        m_window(nullptr) {}

  void cleanup() {
    grouped_expressions.clear();
    copy_fields.clear();
  }
};

#endif  // TEMP_TABLE_PARAM_INCLUDED