Base class for structured and hierarchical EXPLAIN output formatters. More...

#include <opt_explain_format.h>

Inheritance diagram for Explain_format:

Public Member Functions
virtual	~Explain_format ()=default

virtual bool	is_hierarchical () const =0
	A hierarchical text or a plain table. More...

virtual bool	is_iterator_based (THD explain_thd, const THD query_thd) const
	Whether the format closely resembles the final plan to be executed by execution iterators (See RowIterator). More...

bool	is_explain_into () const
	Whether the output of an EXPLAIN statement should be stored in a user variable or sent to the client. More...

bool	is_explain_for_schema () const
	Whether the EXPLAIN statement should be run in another schema than the current active schema. More...

std::string_view	explain_into_variable_name () const
	Returns the name of the user variable the output of this EXPLAIN statement is to be stored in. More...

virtual bool	send_headers (Query_result *result)
	Send EXPLAIN header item(s) to output stream. More...

virtual bool	begin_context (enum_parsing_context context, Query_expression subquery=nullptr, const Explain_format_flags flags=nullptr)=0
	Enter a specified context. More...

virtual bool	end_context (enum_parsing_context context)=0
	Leave the current context. More...

virtual bool	flush_entry ()=0
	Flush TABLE/JOIN_TAB property set. More...

virtual qep_row *	entry ()=0
	Get a pointer to the current TABLE/JOIN_TAB property set. More...

virtual std::string	ExplainJsonToString (Json_object *json)
	Convert Json object to string. More...

Public Attributes
LEX_CSTRING	m_schema_name_for_explain

Protected Member Functions
	Explain_format ()

	Explain_format (std::optional< std::string_view > explain_into_variable_name)

Protected Attributes
Query_result *	output
	output resulting data there More...

Private Member Functions
	Explain_format (Explain_format &)

Explain_format &	operator= (Explain_format &)

Private Attributes
std::optional< std::string_view >	m_explain_into_variable_name

Detailed Description

Base class for structured and hierarchical EXPLAIN output formatters.

Constructor & Destructor Documentation

◆ Explain_format() [1/3]

Explain_format::Explain_format ( Explain_format & )

private

◆ Explain_format() [2/3]

Explain_format::Explain_format ( )

inlineprotected

◆ Explain_format() [3/3]

Explain_format::Explain_format ( std::optional< std::string_view > explain_into_variable_name )

inlineexplicitprotected

◆ ~Explain_format()

virtual Explain_format::~Explain_format ( )

virtualdefault

Member Function Documentation

◆ begin_context()

virtual bool Explain_format::begin_context	(	enum_parsing_context	context,
		Query_expression *	subquery = `nullptr`,
		const Explain_format_flags *	flags = `nullptr`
	)

pure virtual

Enter a specified context.

Parameters

context	context type
subquery	for CTX_WHERE: unit of the subquery
flags	Format flags, see Explain_format_flags.

Implemented in Explain_format_JSON, Explain_format_traditional, and Explain_format_tree.

◆ end_context()

virtual bool Explain_format::end_context ( enum_parsing_context context )

pure virtual

Leave the current context.

Parameters

context current context type (for validation/debugging)

Implemented in Explain_format_JSON, Explain_format_traditional, and Explain_format_tree.

◆ entry()

virtual qep_row * Explain_format::entry ( )

pure virtual

Get a pointer to the current TABLE/JOIN_TAB property set.

Implemented in Explain_format_JSON, Explain_format_traditional, and Explain_format_tree.

◆ explain_into_variable_name()

std::string_view Explain_format::explain_into_variable_name ( ) const

inline

Returns the name of the user variable the output of this EXPLAIN statement is to be stored in.

Should only be called if this is an EXPLAIN INTO statement.

Returns: std::string_view The name of the variable to store the output in.

◆ ExplainJsonToString()

virtual std::string Explain_format::ExplainJsonToString ( Json_object * json )

inlinevirtual

Convert Json object to string.

Should only be called for iterator-based formats.

Reimplemented in Explain_format_JSON, and Explain_format_tree.

◆ flush_entry()

virtual bool Explain_format::flush_entry ( )

pure virtual

Flush TABLE/JOIN_TAB property set.

For traditional EXPLAIN: output a single EXPLAIN row.

Implemented in Explain_format_JSON, Explain_format_traditional, and Explain_format_tree.

◆ is_explain_for_schema()

bool Explain_format::is_explain_for_schema ( ) const

inline

Whether the EXPLAIN statement should be run in another schema than the current active schema.

If this returns true, m_schema_name_for_explain contains the name of the schema to use for EXPLAIN.

Returns: true The EXPLAIN statement should be run in another schema.; false The EXPLAIN statement should be run in the current active schema.

◆ is_explain_into()

bool Explain_format::is_explain_into ( ) const

inline

Whether the output of an EXPLAIN statement should be stored in a user variable or sent to the client.

If this function returns true, explain_into_variable_name() returns the name of the variable.

Return values

true	EXPLAIN output should be stored in a user variable.
false	EXPLAIN output should be sent to the client.

◆ is_hierarchical()

virtual bool Explain_format::is_hierarchical ( ) const

pure virtual

A hierarchical text or a plain table.

Return values

true	Formatter produces hierarchical text
false	Traditional explain

Implemented in Explain_format_JSON, Explain_format_traditional, and Explain_format_tree.

◆ is_iterator_based()

virtual bool Explain_format::is_iterator_based	(	THD *	explain_thd,
		const THD *	query_thd
	)		const

inlinevirtual

Whether the format closely resembles the final plan to be executed by execution iterators (See RowIterator).

These formats share a common logic that uses AccessPath structure to generate the information, so they all display exactly the same information, even though the style of each format might be different.

Note: : The new json format for hypergraph and the tree format are examples of iterator-based formats.

Return values

true	Format is Iterator-based.
false	Format is not Iterator-based.

Reimplemented in Explain_format_JSON, and Explain_format_tree.

◆ operator=()

Explain_format & Explain_format::operator= ( Explain_format & )

private

◆ send_headers()

virtual bool Explain_format::send_headers ( Query_result * result )

inlinevirtual

Send EXPLAIN header item(s) to output stream.

Note: : This function caches the output result set pointer for further use.

Parameters

result output result set

Return values

false	OK
true	Error

Reimplemented in Explain_format_tree, Explain_format_JSON, and Explain_format_traditional.

Member Data Documentation

◆ m_explain_into_variable_name

std::optional<std::string_view> Explain_format::m_explain_into_variable_name

private

◆ m_schema_name_for_explain

LEX_CSTRING Explain_format::m_schema_name_for_explain

◆ output

Query_result* Explain_format::output

protected

output resulting data there

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

sql/opt_explain_format.h

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Explain_format() [1/3]

◆ Explain_format() [2/3]

◆ Explain_format() [3/3]

◆ ~Explain_format()

Member Function Documentation

◆ begin_context()

◆ end_context()

◆ entry()

◆ explain_into_variable_name()

◆ ExplainJsonToString()

◆ flush_entry()

◆ is_explain_for_schema()

◆ is_explain_into()

◆ is_hierarchical()

◆ is_iterator_based()

◆ operator=()

◆ send_headers()

Member Data Documentation

◆ m_explain_into_variable_name

◆ m_schema_name_for_explain

◆ output