opt_explain_json_namespace::message_ctx Class Reference

Inheritance diagram for opt_explain_json_namespace::message_ctx:

List of all members.

Public Member Functions
	message_ctx (context *parent_arg)
virtual bool	format_body (Opt_trace_context *json, Opt_trace_object *obj)
virtual size_t	id (bool hide)
virtual bool	cacheable ()
virtual bool	dependent ()
virtual qep_row *	entry ()
virtual bool	format_derived (Opt_trace_context *json)
	Helper function to format output for derived subquery if any.
virtual bool	format_where (Opt_trace_context *json)
	Helper function to format output for associated WHERE subqueries if any.
virtual bool	find_and_set_derived (context *subquery)
virtual bool	add_where_subquery (subquery_ctx *ctx, SELECT_LEX_UNIT *subquery)

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Detailed Description

Node class for CTX_MESSAGE

This class is designed to represent fake tables with some messages in the "extra" column ("Impossible where" etc). We do EXPLAIN of these fake tables to replace explanation of: 1) usual actual JOIN_TABs of the whole JOIN or 2) a modifying TABLE of single-table UPDATE/DELETE/etc. So, message_ctx always represent a single half-empty fake table in a "query_block" node with optional subqueries.

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Member Function Documentation

virtual bool opt_explain_json_namespace::message_ctx::add_where_subquery	(	subquery_ctx *	ctx,
		SELECT_LEX_UNIT *	subquery
	)		[inline, virtual]

Associate WHERE subqueries of given context and unit with this object

Parameters:

ctx	Context of WHERE subquery
subquery	For CTX_JOIN_TAB: match given unit with a previously collected by the register_where_subquery function.

Reimplemented from opt_explain_json_namespace::context.

virtual bool opt_explain_json_namespace::message_ctx::find_and_set_derived

(

context *

subquery

)

[inline, virtual]

Try to associate a derived subquery node with this or underlying node

Parameters:

subquery

Derived subquery node

Return values:

true	Success
false	Can't associate: this node or its child nodes are not derived from the subquery

Reimplemented from opt_explain_json_namespace::context.

virtual bool opt_explain_json_namespace::message_ctx::format_body	(	Opt_trace_context *	json,
		Opt_trace_object *	obj
	)		[inline, virtual]

Format JSON object body

Parameters:

json	Formatter
obj	Object of this body

Return values:

false	Ok
true	Error

Implements opt_explain_json_namespace::context.

virtual size_t opt_explain_json_namespace::message_ctx::id

(

bool

hide

)

[inline, virtual]

Analogue of the "id" column in the traditional EXPLAIN output

Parameters:

hide	if true, ban the output of K_SELECT_ID JSON property in the underlying table_with_where_and_derived_ctx objects

Returns:

"Select number" that is associated with this node

Reimplemented from opt_explain_json_namespace::table_with_where_and_derived.

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

• opt_explain_json.cc