PT_locking Class Reference

#include <parse_tree_nodes.h>

Inheritance diagram for PT_locking:

Public Member Functions
	PT_locking (PT_query_expression_body *qe, PT_locking_clause_list *locking_clauses)
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 Types
using	super = PT_query_expression_body

Private Attributes
PT_query_expression_body *const	m_query_expression
PT_locking_clause_list *const	m_locking_clauses

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 ()

Member Typedef Documentation

super

using PT_locking::super = PT_query_expression_body

private

Constructor & Destructor Documentation

PT_locking()

PT_locking::PT_locking ( PT_query_expression_body *  qe, PT_locking_clause_list *  locking_clauses  )

inline

Member Function Documentation

can_absorb_order_and_limit()

bool PT_locking::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_locking::contextualize ( Parse_context *  pc )

inlineoverride

get_row_value_list()

PT_insert_values_list * PT_locking::get_row_value_list ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

has_into_clause()

bool PT_locking::has_into_clause ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

has_trailing_into_clause()

bool PT_locking::has_trailing_into_clause ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

is_set_operation()

bool PT_locking::is_set_operation ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

is_table_value_constructor()

bool PT_locking::is_table_value_constructor ( ) const

inlineoverridevirtual

Implements PT_query_expression_body.

Member Data Documentation

m_locking_clauses

PT_locking_clause_list* const PT_locking::m_locking_clauses

private

m_query_expression

PT_query_expression_body* const PT_locking::m_query_expression

private

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

• sql/parse_tree_nodes.h