MySQL 8.3.0
Source Code Documentation
PT_query_expression_body Class Referenceabstract

#include <parse_tree_nodes.h>

Inheritance diagram for PT_query_expression_body:
[legend]

Public Member Functions

 PT_query_expression_body (const POS &pos)
 
virtual bool is_set_operation () const =0
 
virtual bool can_absorb_order_and_limit (bool order, bool limit) const =0
 True if this query expression can absorb an extraneous order by/limit clause. More...
 
virtual bool has_into_clause () const =0
 
virtual bool has_trailing_into_clause () const =0
 
virtual bool is_table_value_constructor () const =0
 
virtual PT_insert_values_listget_row_value_list () const =0
 
- 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) final
 
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...
 

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
 
- Public Attributes inherited from Parse_tree_node_tmpl< Context >
POS m_pos
 
- Protected Member Functions inherited from Parse_tree_node_tmpl< Context >
 Parse_tree_node_tmpl ()=delete
 
 Parse_tree_node_tmpl (const POS &pos)
 
 Parse_tree_node_tmpl (const POS &start_pos, const POS &end_pos)
 
bool begin_parse_tree (Show_parse_tree *tree)
 
bool end_parse_tree (Show_parse_tree *tree)
 
virtual bool do_contextualize (Context *pc)
 Do all context-sensitive things and mark the node as contextualized. More...
 
virtual void add_json_info (Json_object *json_obj)
 Add all the node-specific json fields. More...
 

Constructor & Destructor Documentation

◆ PT_query_expression_body()

PT_query_expression_body::PT_query_expression_body ( const POS pos)
inlineexplicit

Member Function Documentation

◆ can_absorb_order_and_limit()

virtual bool PT_query_expression_body::can_absorb_order_and_limit ( bool  order,
bool  limit 
) const
pure virtual

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
orderTrue if the outer query block has the ORDER BY clause.
limitTrue if the outer query block has the LIMIT clause.

Implemented in PT_query_expression, PT_locking, PT_query_specification, PT_table_value_constructor, and PT_set_operation.

◆ get_row_value_list()

virtual PT_insert_values_list * PT_query_expression_body::get_row_value_list ( ) const
pure virtual

◆ has_into_clause()

virtual bool PT_query_expression_body::has_into_clause ( ) const
pure virtual

◆ has_trailing_into_clause()

virtual bool PT_query_expression_body::has_trailing_into_clause ( ) const
pure virtual

◆ is_set_operation()

virtual bool PT_query_expression_body::is_set_operation ( ) const
pure virtual

◆ is_table_value_constructor()

virtual bool PT_query_expression_body::is_table_value_constructor ( ) const
pure virtual

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