A base for all Explain_* classes. More...

Inheritance diagram for anonymous_namespace{opt_explain.cc}::Explain:

Classes
class	Lazy_condition

Public Member Functions
virtual	~Explain ()=default

bool	send ()
	Explain class main function. More...

bool	can_print_clauses () const
	Tells if it is allowed to print the WHERE / GROUP BY / etc clauses. More...

Protected Member Functions
	Explain (enum_parsing_context context_type_arg, THD explain_thd_arg, const THD query_thd_arg, Query_block *query_block_arg)

virtual bool	shallow_explain ()
	Explain everything but subqueries. More...

bool	explain_subqueries ()
	Explain the rest of things after the `shallow_explain()` call. More...

bool	mark_subqueries (Item item, qep_row destination)
	Qualify subqueries with WHERE/HAVING/ORDER BY/GROUP BY clause type marker. More...

bool	prepare_columns ()
	Pre-calculate table property values for further EXPLAIN output. More...

bool	push_extra (Extra_tag tag)
	Push a part of the "extra" column into formatter. More...

bool	push_extra (Extra_tag tag, const String &arg)
	Push a part of the "extra" column into formatter. More...

bool	push_extra (Extra_tag tag, const char *arg)
	Push a part of the "extra" column into formatter. More...

virtual bool	explain_id ()

virtual bool	explain_select_type ()

virtual bool	explain_table_name ()

virtual bool	explain_partitions ()

virtual bool	explain_join_type ()

virtual bool	explain_possible_keys ()

virtual bool	explain_key_and_len ()
	fill col_key and and col_key_len fields together More...

virtual bool	explain_ref ()

virtual bool	explain_rows_and_filtered ()
	fill col_rows and col_filtered fields together More...

virtual bool	explain_extra ()

virtual bool	explain_modify_flags ()

virtual bool	can_walk_clauses ()
	Returns true if the WHERE, ORDER BY, GROUP BY, etc clauses can safely be traversed: it means that we can iterate through them (no element is added/removed/replaced); the internal details of an element can change though (in particular if that element is an Item_subselect). More...

virtual enum_parsing_context	get_subquery_context (Query_expression *unit) const

Protected Attributes
THD *const	explain_thd
	cached THD which runs the EXPLAIN command More...

const THD *	query_thd
	THD which runs the query to be explained. More...

const CHARSET_INFO *const	cs
	cached pointer to system_charset_info More...

Query_block *const	query_block
	Cached Query_block of the explained query. More...

Explain_format *const	fmt
	shortcut for thd->lex->explain_format More...

enum_parsing_context	context_type
	associated value for struct. explain More...

bool	order_list
	if query block has ORDER BY More...

const bool	explain_other
	if we explain other thread than us More...

Private Member Functions
virtual bool	skip_subqueries () const
	Returns true if EXPLAIN should not produce any information about subqueries. More...

Detailed Description

A base for all Explain_* classes.

Explain_* classes collect and output EXPLAIN data.

This class hierarchy is a successor of the old select_describe() function of 5.5.

Constructor & Destructor Documentation

◆ Explain()

anonymous_namespace{opt_explain.cc}::Explain::Explain	(	enum_parsing_context	context_type_arg,
		THD *	explain_thd_arg,
		const THD *	query_thd_arg,
		Query_block *	query_block_arg
	)

inlineexplicitprotected

◆ ~Explain()

virtual anonymous_namespace{opt_explain.cc}::Explain::~Explain ( )

virtualdefault

Member Function Documentation

◆ can_print_clauses()

bool anonymous_namespace{opt_explain.cc}::Explain::can_print_clauses ( ) const

inline

Tells if it is allowed to print the WHERE / GROUP BY / etc clauses.

◆ can_walk_clauses()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::can_walk_clauses ( )

inlineprotectedvirtual

Returns true if the WHERE, ORDER BY, GROUP BY, etc clauses can safely be traversed: it means that we can iterate through them (no element is added/removed/replaced); the internal details of an element can change though (in particular if that element is an Item_subselect).

By default, if we are explaining another connection, this is not safe.

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_setop_result, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_extra()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_extra ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_no_table, anonymous_namespace{opt_explain.cc}::Explain_setop_result, anonymous_namespace{opt_explain.cc}::Explain_join, anonymous_namespace{opt_explain.cc}::Explain_table, and anonymous_namespace{opt_explain.cc}::Explain_secondary_engine.

◆ explain_id()

bool Explain::explain_id ( )

protectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_setop_result, and anonymous_namespace{opt_explain.cc}::Explain_join.

◆ explain_join_type()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_join_type ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_setop_result, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_key_and_len()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_key_and_len ( )

inlineprotectedvirtual

fill col_key and and col_key_len fields together

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_modify_flags()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_modify_flags ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_no_table, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_partitions()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_partitions ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_table_base.

◆ explain_possible_keys()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_possible_keys ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_table_base.

◆ explain_ref()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_ref ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_rows_and_filtered()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_rows_and_filtered ( )

inlineprotectedvirtual

fill col_rows and col_filtered fields together

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_no_table, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ explain_select_type()

bool Explain::explain_select_type ( )

protectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_secondary_engine.

◆ explain_subqueries()

bool Explain::explain_subqueries ( )

protected

Explain the rest of things after the shallow_explain() call.

Traverses SQL clauses of this query specification to identify children subqueries, marks each of them with the clause they belong to.

Then goes though all children subqueries and produces their EXPLAIN output, attached to the proper clause's context.

Return values

false	Ok
true	Error (OOM)

◆ explain_table_name()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::explain_table_name ( )

inlineprotectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_setop_result, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ get_subquery_context()

enum_parsing_context anonymous_namespace{opt_explain.cc}::Explain::get_subquery_context ( Query_expression * unit ) const

protectedvirtual

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_no_table.

◆ mark_subqueries()

bool Explain::mark_subqueries	(	Item *	item,
		qep_row *	destination
	)

protected

Qualify subqueries with WHERE/HAVING/ORDER BY/GROUP BY clause type marker.

Parameters

item	Item tree to find subqueries
destination	For WHERE clauses

Note: WHERE clause belongs to TABLE or QEP_TAB. The destination parameter provides a pointer to QEP data for such a table to associate a future subquery EXPLAIN output with table QEP provided.

Return values

false	OK
true	Error

◆ prepare_columns()

bool Explain::prepare_columns ( )

protected

Pre-calculate table property values for further EXPLAIN output.

◆ push_extra() [1/3]

bool anonymous_namespace{opt_explain.cc}::Explain::push_extra ( Extra_tag tag )

inlineprotected

Push a part of the "extra" column into formatter.

Traditional formatter outputs traditional_extra_tags[tag] as is. Hierarchical formatter outputs a property with the json_extra_tags[tag] name and a boolean value of true.

Parameters

tag	type of the "extra" part

Return values

false	Ok
true	Error (OOM)

◆ push_extra() [2/3]

bool anonymous_namespace{opt_explain.cc}::Explain::push_extra	(	Extra_tag	tag,
		const char *	arg
	)

inlineprotected

Push a part of the "extra" column into formatter.

Parameters

tag	type of the "extra" part
arg	for traditional formatter: rest of the part text, for hierarchical format: string value of the property

NOTE: arg must be a long-living string constant.

Return values

false	Ok
true	Error (OOM)

◆ push_extra() [3/3]

bool anonymous_namespace{opt_explain.cc}::Explain::push_extra	(	Extra_tag	tag,
		const String &	arg
	)

inlineprotected

Push a part of the "extra" column into formatter.

Parameters

tag	type of the "extra" part
arg	for traditional formatter: rest of the part text, for hierarchical format: string value of the property

Return values

false	Ok
true	Error (OOM)

◆ send()

bool Explain::send ( )

Explain class main function.

This function: a) allocates a Query_result_send object (if no one pre-allocated available), b) calculates and sends whole EXPLAIN data.

Returns: false if success, true if error

◆ shallow_explain()

bool Explain::shallow_explain ( )

protectedvirtual

Explain everything but subqueries.

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_no_table, anonymous_namespace{opt_explain.cc}::Explain_join, and anonymous_namespace{opt_explain.cc}::Explain_table.

◆ skip_subqueries()

virtual bool anonymous_namespace{opt_explain.cc}::Explain::skip_subqueries ( ) const

inlineprivatevirtual

Returns true if EXPLAIN should not produce any information about subqueries.

Reimplemented in anonymous_namespace{opt_explain.cc}::Explain_secondary_engine.

Member Data Documentation

◆ context_type

enum_parsing_context anonymous_namespace{opt_explain.cc}::Explain::context_type

protected

associated value for struct. explain

◆ cs

const CHARSET_INFO* const anonymous_namespace{opt_explain.cc}::Explain::cs

protected

cached pointer to system_charset_info

◆ explain_other

const bool anonymous_namespace{opt_explain.cc}::Explain::explain_other

protected

if we explain other thread than us

◆ explain_thd

THD* const anonymous_namespace{opt_explain.cc}::Explain::explain_thd

protected

cached THD which runs the EXPLAIN command

◆ fmt

Explain_format* const anonymous_namespace{opt_explain.cc}::Explain::fmt

protected

shortcut for thd->lex->explain_format

◆ order_list

bool anonymous_namespace{opt_explain.cc}::Explain::order_list

protected

if query block has ORDER BY

◆ query_block

Query_block* const anonymous_namespace{opt_explain.cc}::Explain::query_block

protected

Cached Query_block of the explained query.

Used for all explained stmts, including single-table UPDATE (provides way to access ORDER BY of UPDATE).

◆ query_thd

const THD* anonymous_namespace{opt_explain.cc}::Explain::query_thd

protected

THD which runs the query to be explained.

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

sql/opt_explain.cc

Classes

Public Member Functions

Protected Member Functions

Protected Attributes

Private Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ Explain()

◆ ~Explain()

Member Function Documentation

◆ can_print_clauses()

◆ can_walk_clauses()

◆ explain_extra()

◆ explain_id()

◆ explain_join_type()

◆ explain_key_and_len()

◆ explain_modify_flags()

◆ explain_partitions()

◆ explain_possible_keys()

◆ explain_ref()

◆ explain_rows_and_filtered()

◆ explain_select_type()

◆ explain_subqueries()

◆ explain_table_name()

◆ get_subquery_context()

◆ mark_subqueries()

◆ prepare_columns()

◆ push_extra() [1/3]

◆ push_extra() [2/3]

◆ push_extra() [3/3]

◆ send()

◆ shallow_explain()

◆ skip_subqueries()

Member Data Documentation

◆ context_type

◆ cs

◆ explain_other

◆ explain_thd

◆ fmt

◆ order_list

◆ query_block

◆ query_thd