PT_query_expression Class Reference

#include <parse_tree_nodes.h>

Inheritance diagram for PT_query_expression:

Public Member Functions
	PT_query_expression (PT_with_clause *with_clause, PT_query_expression_body *body, PT_order *order, PT_limit_clause *limit)
	PT_query_expression (PT_query_expression_body *body, PT_order *order, PT_limit_clause *limit)
	PT_query_expression (PT_query_expression_body *body)
bool	contextualize (Parse_context *pc) override
bool	is_set_operation () const override
bool	has_into_clause () const override
bool	has_trailing_into_clause () const override
bool	can_absorb_order_and_limit (bool order, bool limit) const override
	True if this query expression can absorb an extraneous order by/limit clause. More...
bool	is_table_value_constructor () const override
PT_insert_values_list *	get_row_value_list () const override
Public Member Functions inherited from Parse_tree_node_tmpl< Context >
virtual	~Parse_tree_node_tmpl ()=default
bool	is_contextualized () const
virtual bool	contextualize (Context *pc)
	Do all context-sensitive things and mark the node as contextualized. More...
void	error (Context *pc, const POS &pos) const
	syntax_error() function replacement for deferred reporting of syntax errors More...
void	error (Context *pc, const POS &pos, const char *msg) const
	syntax_error() function replacement for deferred reporting of syntax errors More...
void	errorf (Context *pc, const POS &pos, const char *format,...) const
	syntax_error() function replacement for deferred reporting of syntax errors More...

Private Member Functions
bool	contextualize_order_and_limit (Parse_context *pc)
	Contextualizes the order and limit clauses, re-interpreting them according to the rules. More...

Private Attributes
PT_query_expression_body *	m_body
PT_order *	m_order
PT_limit_clause *	m_limit
PT_with_clause *	m_with_clause

Additional Inherited Members
Public Types inherited from Parse_tree_node_tmpl< Context >
typedef Context	context_t
Static Public Member Functions inherited from Parse_tree_node_tmpl< Context >
static void *	operator new (size_t size, MEM_ROOT *mem_root, const std::nothrow_t &arg=std::nothrow) noexcept
static void	operator delete (void *ptr, size_t size)
static void	operator delete (void *, MEM_ROOT *, const std::nothrow_t &) noexcept
Protected Member Functions inherited from Parse_tree_node_tmpl< Context >
	Parse_tree_node_tmpl ()

Constructor & Destructor Documentation

PT_query_expression() [1/3]

PT_query_expression::PT_query_expression ( PT_with_clause *  with_clause, PT_query_expression_body *  body, PT_order *  order, PT_limit_clause *  limit  )

inline

PT_query_expression() [2/3]

PT_query_expression::PT_query_expression ( PT_query_expression_body *  body, PT_order *  order, PT_limit_clause *  limit  )

inline

PT_query_expression() [3/3]

PT_query_expression::PT_query_expression ( PT_query_expression_body *  body )

inlineexplicit

Member Function Documentation

can_absorb_order_and_limit()

bool PT_query_expression::can_absorb_order_and_limit ( bool  order, bool  limit  ) const

inlineoverridevirtual

True if this query expression can absorb an extraneous order by/limit clause.

The ORDER BY/LIMIT syntax is mostly consistestent, i.e. a trailing clause may not refer to the tables in the <query primary>, with one glaring exception:

(...( SELECT ... )...) ORDER BY ...

If the nested query expression doesn't contain ORDER BY, the statement is interpreted as if the ORDER BY was absorbed by the innermost query expression, i.e.:

(...( SELECT ... ORDER BY ... )...)

There is no rewriting of the parse tree nor AST happening here, the transformation is done by the contextualizer (see PT_query_expression::contextualize_order_and_limit), which interprets the parse tree, and builds the AST according to this interpretation. This interpretation is governed by the following rule: An ORDER BY can be absorbed if none the nested query expressions contains an ORDER BY or LIMIT. The rule is complex, so here are some examples for illustration:

In these cases the ORDER BY is absorbed:

( SELECT * FROM t1 ) ORDER BY t1.a;
(( SELECT * FROM t1 )) ORDER BY t1.a;

In these cases the ORDER BY is not absorbed:

( SELECT * FROM t1 ORDER BY 1 ) ORDER BY t1.a;
(( SELECT * FROM t1 ) ORDER BY 1 ) ORDER BY t1.a;
( SELECT * FROM t1 LIMIT 1 ) ORDER BY t1.a;
(( SELECT * FROM t1 ) LIMIT 1 ) ORDER BY t1.a;

The same happens with LIMIT, obviously, but the optimizer is freeer to choose when to apply the limit, and there are name no resolution issues involved.

Parameters

order	True if the outer query block has the ORDER BY clause.
limit	True if the outer query block has the LIMIT clause.

Implements PT_query_expression_body.

contextualize()

bool PT_query_expression::contextualize ( Parse_context *  pc )

override

contextualize_order_and_limit()

bool PT_query_expression::contextualize_order_and_limit ( Parse_context *  pc )

private

Contextualizes the order and limit clauses, re-interpreting them according to the rules.

If the <query expression body> can absorb the clauses, they are simply contextualized into the current Query_block. If not, we have to create the "fake" Query_block unless there is one already (Query_expression::new_set_operation_query() is known to do this.)

See also

PT_query_expression::can_absorb_order_and_limit()

get_row_value_list()

PT_insert_values_list * PT_query_expression::get_row_value_list ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

has_into_clause()

bool PT_query_expression::has_into_clause ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

has_trailing_into_clause()

bool PT_query_expression::has_trailing_into_clause ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

is_set_operation()

bool PT_query_expression::is_set_operation ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

is_table_value_constructor()

bool PT_query_expression::is_table_value_constructor ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

Member Data Documentation

m_body

PT_query_expression_body* PT_query_expression::m_body

private

m_limit

PT_limit_clause* PT_query_expression::m_limit

private

m_order

PT_order* PT_query_expression::m_order

private

m_with_clause

PT_with_clause* PT_query_expression::m_with_clause

private

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

• sql/parse_tree_nodes.h
• sql/parse_tree_nodes.cc