index_skip_scan.h

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#ifndef SQL_RANGE_OPTIMIZER_INDEX_SKIP_SCAN_H_
#define SQL_RANGE_OPTIMIZER_INDEX_SKIP_SCAN_H_
 
#include <sys/types.h>
 
#include "my_alloc.h"
#include "my_base.h"
#include "my_bitmap.h"
#include "my_inttypes.h"
#include "sql/field.h"  // Field
#include "sql/key.h"
#include "sql/malloc_allocator.h"  // IWYU pragma: keep
#include "sql/range_optimizer/index_skip_scan_plan.h"
#include "sql/range_optimizer/range_optimizer.h"
 
class Cost_estimate;
class JOIN;
class SEL_ARG;
class SEL_ROOT;
class String;
struct TABLE;
 
/*
  Index scan for range queries that can use skip scans.
 
  This class provides a specialized index access method for the queries
  of the forms:
 
       SELECT A_1,...,A_k, B_1,...,B_m, C
         FROM T
        WHERE
         EQ(A_1,...,A_k)
         AND RNG(C);
 
  where all selected fields are parts of the same index.
  The class of queries that can be processed by this quick select is fully
  specified in the description of get_best_skip_scan() in opt_range.cc.
 
  Since one of the requirements is that all select fields are part of the same
  index, this class produces only index keys, and not complete records.
*/
 
class IndexSkipScanIterator final : public TableRowIterator {
 private:
  uint index;              /* Index this quick select uses */
  KEY *index_info;         /* Index for skip scan */
  MY_BITMAP column_bitmap; /* Map of key parts to be read */
 
  const uint eq_prefix_len; /* Total length of the equality prefix. */
  uint eq_prefix_key_parts; /* A number of keyparts in skip scan prefix */
  EQPrefix *eq_prefixes;
  uchar *eq_prefix; /* Storage for current equality prefix. */
 
  // Total length of first used_key_parts parts of the key.
  uint max_used_key_length;
 
  // Max. number of (first) key parts this quick select uses for retrieval.
  // eg. for "(key1p1=c1 AND key1p2=c2) OR key1p1=c2" used_key_parts == 2.
  uint used_key_parts;
 
  uchar *distinct_prefix; /* Storage for prefix A_1, ... B_m. */
  uint distinct_prefix_len;
  uint distinct_prefix_key_parts;
 
  MEM_ROOT *mem_root;
  const uint range_key_len;
  /*
    Denotes whether the first key for the current equality prefix was
    retrieved.
  */
  bool seen_first_key;
 
  /* Storage for full lookup key for use with handler::read_range_first/next */
  uchar *const min_range_key;
  uchar *const max_range_key;
  uchar *const min_search_key;
  uchar *const max_search_key;
  const uint range_cond_flag;
 
  key_range start_key;
  key_range end_key;
 
  bool has_aggregate_function;
 
  bool next_eq_prefix();
 
 public:
  IndexSkipScanIterator(THD *thd, TABLE *table, KEY *index_info, uint index,
                        uint eq_prefix_len, uint eq_prefix_key_parts,
                        EQPrefix *eq_prefixes, uint used_key_parts,
                        MEM_ROOT *temp_mem_root, bool has_aggregate_function,
                        uchar *min_range_key, uchar *max_range_key,
                        uchar *min_search_key, uchar *max_search_key,
                        uint range_cond_flag, uint range_key_len);
  ~IndexSkipScanIterator() override;
 
 private:
  bool DoInit() override;
  int DoRead() override;
};
 
#endif  // SQL_RANGE_OPTIMIZER_INDEX_SKIP_SCAN_H_