SEL_TREE Class Reference

Inheritance diagram for SEL_TREE:

List of all members.

Public Types
enum	Type {   IMPOSSIBLE, ALWAYS, MAYBE, KEY,   KEY_SMALLER }
Public Member Functions
	SEL_TREE (enum Type type_arg)
	SEL_TREE (SEL_TREE *arg, RANGE_OPT_PARAM *param)
Public Attributes
enum SEL_TREE::Type	type
SEL_ARG *	keys [MAX_KEY]
key_map	keys_map
List< SEL_IMERGE >	merges
key_map	ror_scans_map
uint	n_ror_scans
struct st_ror_scan_info **	ror_scans
struct st_ror_scan_info **	ror_scans_end

---

Member Enumeration Documentation

enum SEL_TREE::Type

Starting an effort to document this field:

IMPOSSIBLE: if keys[i]->type == SEL_ARG::IMPOSSIBLE for some i, then type == SEL_TREE::IMPOSSIBLE. Rationale: if the predicate for one of the indexes is always false, then the full predicate is also always false.

ALWAYS: if either (keys[i]->type == SEL_ARG::ALWAYS) or (keys[i] == NULL) for all i, then type == SEL_TREE::ALWAYS. Rationale: the range access method will not be able to filter out any rows when there are no range predicates that can be used to filter on any index.

KEY: There are range predicates that can be used on at least one index.

KEY_SMALLER: There are range predicates that can be used on at least one index. In addition, there are predicates that cannot be directly utilized by range access on key parts in the same index. These unused predicates makes it probable that the row estimate for range access on this index is too pessimistic.

---

The documentation for this class was generated from the following file:

• opt_range.cc