Explain_format Class Reference

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

#include <opt_explain_format.h>

Inheritance diagram for Explain_format:

Public Member Functions
	Explain_format ()
virtual	~Explain_format ()=default
virtual bool	is_hierarchical () const =0
	A hierarchical text or a plain table. More...
virtual bool	is_iterator_based () const
	Whether the format closely resembles the final plan to be executed by execution iterators (See RowIterator). 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...

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

Private Member Functions
	Explain_format (Explain_format &)
Explain_format &	operator= (Explain_format &)

Detailed Description

Base class for structured and hierarchical EXPLAIN output formatters.

Constructor & Destructor Documentation

Explain_format() [1/2]

Explain_format::Explain_format ( Explain_format &  )

private

Explain_format() [2/2]

Explain_format::Explain_format ( )

inline

~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.

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_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 ( ) 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

output

Query_result* Explain_format::output

protected

output resulting data there

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

• sql/opt_explain_format.h