AQP Namespace Reference

Classes
class	Join_plan
class	Equal_set_iterator
class	Table_access
Enumerations
enum	enum_access_type {   AT_VOID, AT_FIXED, AT_PRIMARY_KEY, AT_UNIQUE_KEY,   AT_ORDERED_INDEX_SCAN, AT_MULTI_PRIMARY_KEY, AT_MULTI_UNIQUE_KEY, AT_MULTI_MIXED,   AT_TABLE_SCAN, AT_UNDECIDED, AT_OTHER }
enum	enum_join_type { JT_OUTER_JOIN, JT_INNER_JOIN, JT_SEMI_JOIN }

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Detailed Description

Abstract query plan (AQP) is an interface for examining certain aspects of query plans without accessing mysqld internal classes (JOIN_TAB, SQL_SELECT etc.) directly.

AQP maps join execution plans, as represented by mysqld internals, to a set of facade classes. Non-join operations such as sorting and aggregation is currently *not* modelled in the AQP.

The AQP models an n-way join as a sequence of the n table access operations that the MySQL server would execute as part of its nested loop join execution. (Each such table access operation is a scan of a table or index, or an index lookup.) For each lookup operation, it is possible to examine the expression that represents each field in the key.

A storage enging will typically use the AQP for finding sections of a join execution plan that may be executed in the engine rather than in mysqld. By using the AQP rather than the mysqld internals directly, the coupling between the engine and mysqld is reduced.

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Enumeration Type Documentation

enum AQP::enum_access_type

The type of a table access operation.

Enumerator:

AT_VOID	For default initialization.
AT_FIXED	Value has already been fetched / determined by optimizer.
AT_PRIMARY_KEY	Do a lookup of a single primary key.
AT_UNIQUE_KEY	Do a lookup of a single unique index key.
AT_ORDERED_INDEX_SCAN	Scan an ordered index with a single upper and lower bound pair.
AT_MULTI_PRIMARY_KEY	Do a multi range read for a set of primary keys.
AT_MULTI_UNIQUE_KEY	Do a multi range read for a set of unique index keys.
AT_MULTI_MIXED	Do a multi range read for a mix of ranges (for which there is an ordered index), and either primary keys or unique index keys.
AT_TABLE_SCAN	Scan a table. (No index is assumed to be used.)
AT_UNDECIDED	Access method will not be chosen before the execution phase.
AT_OTHER	The access method has properties that prevents it from being pushed to a storage engine.

enum AQP::enum_join_type

The type of join operation require