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item.h
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#ifndef ITEM_INCLUDED
#define ITEM_INCLUDED
/* Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include "sql_priv.h" /* STRING_BUFFER_USUAL_SIZE */
#include "unireg.h"
#include "sql_const.h" /* RAND_TABLE_BIT, MAX_FIELD_NAME */
#include "unireg.h" // REQUIRED: for other includes
#include "thr_malloc.h" /* sql_calloc */
#include "field.h" /* Derivation */
#include "sql_array.h"
class Protocol;
struct TABLE_LIST;
void item_init(void); /* Init item functions */
class Item_field;
class user_var_entry;
typedef Bounds_checked_array<Item*> Ref_ptr_array;
static inline uint32
char_to_byte_length_safe(uint32 char_length_arg, uint32 mbmaxlen_arg)
{
ulonglong tmp= ((ulonglong) char_length_arg) * mbmaxlen_arg;
return (tmp > UINT_MAX32) ? (uint32) UINT_MAX32 : (uint32) tmp;
}
/*
"Declared Type Collation"
A combination of collation and its derivation.
Flags for collation aggregation modes:
MY_COLL_ALLOW_SUPERSET_CONV - allow conversion to a superset
MY_COLL_ALLOW_COERCIBLE_CONV - allow conversion of a coercible value
(i.e. constant).
MY_COLL_ALLOW_CONV - allow any kind of conversion
(combination of the above two)
MY_COLL_ALLOW_NUMERIC_CONV - if all items were numbers, convert to
@@character_set_connection
MY_COLL_DISALLOW_NONE - don't allow return DERIVATION_NONE
(e.g. when aggregating for comparison)
MY_COLL_CMP_CONV - combination of MY_COLL_ALLOW_CONV
and MY_COLL_DISALLOW_NONE
*/
#define MY_COLL_ALLOW_SUPERSET_CONV 1
#define MY_COLL_ALLOW_COERCIBLE_CONV 2
#define MY_COLL_DISALLOW_NONE 4
#define MY_COLL_ALLOW_NUMERIC_CONV 8
#define MY_COLL_ALLOW_CONV (MY_COLL_ALLOW_SUPERSET_CONV | MY_COLL_ALLOW_COERCIBLE_CONV)
#define MY_COLL_CMP_CONV (MY_COLL_ALLOW_CONV | MY_COLL_DISALLOW_NONE)
class DTCollation {
public:
const CHARSET_INFO *collation;
enum Derivation derivation;
uint repertoire;
void set_repertoire_from_charset(const CHARSET_INFO *cs)
{
repertoire= cs->state & MY_CS_PUREASCII ?
MY_REPERTOIRE_ASCII : MY_REPERTOIRE_UNICODE30;
}
DTCollation()
{
collation= &my_charset_bin;
derivation= DERIVATION_NONE;
repertoire= MY_REPERTOIRE_UNICODE30;
}
DTCollation(const CHARSET_INFO *collation_arg, Derivation derivation_arg)
{
collation= collation_arg;
derivation= derivation_arg;
set_repertoire_from_charset(collation_arg);
}
void set(DTCollation &dt)
{
collation= dt.collation;
derivation= dt.derivation;
repertoire= dt.repertoire;
}
void set(const CHARSET_INFO *collation_arg, Derivation derivation_arg)
{
collation= collation_arg;
derivation= derivation_arg;
set_repertoire_from_charset(collation_arg);
}
void set(const CHARSET_INFO *collation_arg,
Derivation derivation_arg,
uint repertoire_arg)
{
collation= collation_arg;
derivation= derivation_arg;
repertoire= repertoire_arg;
}
void set_numeric()
{
collation= &my_charset_numeric;
derivation= DERIVATION_NUMERIC;
repertoire= MY_REPERTOIRE_NUMERIC;
}
void set(const CHARSET_INFO *collation_arg)
{
collation= collation_arg;
set_repertoire_from_charset(collation_arg);
}
void set(Derivation derivation_arg)
{ derivation= derivation_arg; }
void set_repertoire(uint repertoire_arg)
{ repertoire= repertoire_arg; }
bool aggregate(DTCollation &dt, uint flags= 0);
bool set(DTCollation &dt1, DTCollation &dt2, uint flags= 0)
{ set(dt1); return aggregate(dt2, flags); }
const char *derivation_name() const
{
switch(derivation)
{
case DERIVATION_NUMERIC: return "NUMERIC";
case DERIVATION_IGNORABLE: return "IGNORABLE";
case DERIVATION_COERCIBLE: return "COERCIBLE";
case DERIVATION_IMPLICIT: return "IMPLICIT";
case DERIVATION_SYSCONST: return "SYSCONST";
case DERIVATION_EXPLICIT: return "EXPLICIT";
case DERIVATION_NONE: return "NONE";
default: return "UNKNOWN";
}
}
};
/*************************************************************************/
/**
Storage for name strings.
Enpowers Simple_cstring with allocation routines from the sql_strmake family.
This class must stay as small as possible as we often
pass it into functions using call-by-value evaluation.
Don't add new members or virual methods into this class!
*/
class Name_string: public Simple_cstring
{
private:
void set_or_copy(const char *str, size_t length, bool is_null_terminated)
{
if (is_null_terminated)
set(str, length);
else
copy(str, length);
}
public:
Name_string(): Simple_cstring() {}
/*
Please do NOT add constructor Name_string(const char *str) !
It will involve hidden strlen() call, which can affect
performance negatively. Use Name_string(str, len) instead.
*/
Name_string(const char *str, size_t length):
Simple_cstring(str, length) {}
Name_string(const LEX_STRING str): Simple_cstring(str) {}
Name_string(const char *str, size_t length, bool is_null_terminated):
Simple_cstring()
{
set_or_copy(str, length, is_null_terminated);
}
Name_string(const LEX_STRING str, bool is_null_terminated):
Simple_cstring()
{
set_or_copy(str.str, str.length, is_null_terminated);
}
/**
Allocate space using sql_strmake() or sql_strmake_with_convert().
*/
void copy(const char *str, size_t length, const CHARSET_INFO *cs);
/**
Variants for copy(), for various argument combinations.
*/
void copy(const char *str, size_t length)
{
copy(str, length, system_charset_info);
}
void copy(const char *str)
{
copy(str, (str ? strlen(str) : 0), system_charset_info);
}
void copy(const LEX_STRING lex)
{
copy(lex.str, lex.length);
}
void copy(const LEX_STRING *lex)
{
copy(lex->str, lex->length);
}
void copy(const Name_string str)
{
copy(str.ptr(), str.length());
}
/**
Compare name to another name in C string, case insensitively.
*/
bool eq(const char *str) const
{
DBUG_ASSERT(str && ptr());
return my_strcasecmp(system_charset_info, ptr(), str) == 0;
}
bool eq_safe(const char *str) const
{
return is_set() && str && eq(str);
}
/**
Compare name to another name in Name_string, case insensitively.
*/
bool eq(const Name_string name) const
{
return eq(name.ptr());
}
bool eq_safe(const Name_string name) const
{
return is_set() && name.is_set() && eq(name);
}
};
#define NAME_STRING(x) Name_string(C_STRING_WITH_LEN(x))
extern const Name_string null_name_string;
/**
Storage for Item names.
Adds "autogenerated" flag and warning functionality to Name_string.
*/
class Item_name_string: public Name_string
{
private:
bool m_is_autogenerated; /* indicates if name of this Item
was autogenerated or set by user */
public:
Item_name_string(): Name_string(), m_is_autogenerated(true)
{ }
Item_name_string(const Name_string name)
:Name_string(name), m_is_autogenerated(true)
{ }
/**
Set m_is_autogenerated flag to the given value.
*/
void set_autogenerated(bool is_autogenerated)
{
m_is_autogenerated= is_autogenerated;
}
/**
Return the auto-generated flag.
*/
bool is_autogenerated() const { return m_is_autogenerated; }
using Name_string::copy;
/**
Copy name together with autogenerated flag.
Produce a warning if name was cut.
*/
void copy(const char *str_arg, size_t length_arg, const CHARSET_INFO *cs_arg,
bool is_autogenerated_arg);
};
/*************************************************************************/
/*
A framework to easily handle different return types for hybrid items
(hybrid item is an item whose operand can be of any type, e.g. integer,
real, decimal).
*/
struct Hybrid_type_traits;
struct Hybrid_type
{
longlong integer;
double real;
/*
Use two decimal buffers interchangeably to speed up += operation
which has no native support in decimal library.
Hybrid_type+= arg is implemented as dec_buf[1]= dec_buf[0] + arg.
The third decimal is used as a handy temporary storage.
*/
my_decimal dec_buf[3];
int used_dec_buf_no;
/*
Traits moved to a separate class to
a) be able to easily change object traits in runtime
b) they work as a differentiator for the union above
*/
const Hybrid_type_traits *traits;
Hybrid_type() {}
/* XXX: add traits->copy() when needed */
Hybrid_type(const Hybrid_type &rhs) :traits(rhs.traits) {}
};
/* Hybryd_type_traits interface + default implementation for REAL_RESULT */
struct Hybrid_type_traits
{
virtual Item_result type() const { return REAL_RESULT; }
virtual void
fix_length_and_dec(Item *item, Item *arg) const;
/* Hybrid_type operations. */
virtual void set_zero(Hybrid_type *val) const { val->real= 0.0; }
virtual void add(Hybrid_type *val, Field *f) const
{ val->real+= f->val_real(); }
virtual void div(Hybrid_type *val, ulonglong u) const
{ val->real/= ulonglong2double(u); }
virtual longlong val_int(Hybrid_type *val, bool unsigned_flag) const
{ return (longlong) rint(val->real); }
virtual double val_real(Hybrid_type *val) const { return val->real; }
virtual my_decimal *val_decimal(Hybrid_type *val, my_decimal *buf) const;
virtual String *val_str(Hybrid_type *val, String *buf, uint8 decimals) const;
static const Hybrid_type_traits *instance();
Hybrid_type_traits() {}
virtual ~Hybrid_type_traits() {}
};
struct Hybrid_type_traits_decimal: public Hybrid_type_traits
{
virtual Item_result type() const { return DECIMAL_RESULT; }
virtual void
fix_length_and_dec(Item *arg, Item *item) const;
/* Hybrid_type operations. */
virtual void set_zero(Hybrid_type *val) const;
virtual void add(Hybrid_type *val, Field *f) const;
virtual void div(Hybrid_type *val, ulonglong u) const;
virtual longlong val_int(Hybrid_type *val, bool unsigned_flag) const;
virtual double val_real(Hybrid_type *val) const;
virtual my_decimal *val_decimal(Hybrid_type *val, my_decimal *buf) const
{ return &val->dec_buf[val->used_dec_buf_no]; }
virtual String *val_str(Hybrid_type *val, String *buf, uint8 decimals) const;
static const Hybrid_type_traits_decimal *instance();
Hybrid_type_traits_decimal() {};
};
struct Hybrid_type_traits_integer: public Hybrid_type_traits
{
virtual Item_result type() const { return INT_RESULT; }
virtual void
fix_length_and_dec(Item *arg, Item *item) const;
/* Hybrid_type operations. */
virtual void set_zero(Hybrid_type *val) const
{ val->integer= 0; }
virtual void add(Hybrid_type *val, Field *f) const
{ val->integer+= f->val_int(); }
virtual void div(Hybrid_type *val, ulonglong u) const
{ val->integer/= (longlong) u; }
virtual longlong val_int(Hybrid_type *val, bool unsigned_flag) const
{ return val->integer; }
virtual double val_real(Hybrid_type *val) const
{ return (double) val->integer; }
virtual my_decimal *val_decimal(Hybrid_type *val, my_decimal *buf) const
{
int2my_decimal(E_DEC_FATAL_ERROR, val->integer, 0, &val->dec_buf[2]);
return &val->dec_buf[2];
}
virtual String *val_str(Hybrid_type *val, String *buf, uint8 decimals) const
{ buf->set(val->integer, &my_charset_bin); return buf;}
static const Hybrid_type_traits_integer *instance();
Hybrid_type_traits_integer() {};
};
void dummy_error_processor(THD *thd, void *data);
void view_error_processor(THD *thd, void *data);
/*
Instances of Name_resolution_context store the information necesary for
name resolution of Items and other context analysis of a query made in
fix_fields().
This structure is a part of SELECT_LEX, a pointer to this structure is
assigned when an item is created (which happens mostly during parsing
(sql_yacc.yy)), but the structure itself will be initialized after parsing
is complete
TODO: move subquery of INSERT ... SELECT and CREATE ... SELECT to
separate SELECT_LEX which allow to remove tricks of changing this
structure before and after INSERT/CREATE and its SELECT to make correct
field name resolution.
*/
struct Name_resolution_context: Sql_alloc
{
/*
The name resolution context to search in when an Item cannot be
resolved in this context (the context of an outer select)
*/
Name_resolution_context *outer_context;
/*
List of tables used to resolve the items of this context. Usually these
are tables from the FROM clause of SELECT statement. The exceptions are
INSERT ... SELECT and CREATE ... SELECT statements, where SELECT
subquery is not moved to a separate SELECT_LEX. For these types of
statements we have to change this member dynamically to ensure correct
name resolution of different parts of the statement.
*/
TABLE_LIST *table_list;
/*
In most cases the two table references below replace 'table_list' above
for the purpose of name resolution. The first and last name resolution
table references allow us to search only in a sub-tree of the nested
join tree in a FROM clause. This is needed for NATURAL JOIN, JOIN ... USING
and JOIN ... ON.
*/
TABLE_LIST *first_name_resolution_table;
/*
Last table to search in the list of leaf table references that begins
with first_name_resolution_table.
*/
TABLE_LIST *last_name_resolution_table;
/*
SELECT_LEX item belong to, in case of merged VIEW it can differ from
SELECT_LEX where item was created, so we can't use table_list/field_list
from there
*/
st_select_lex *select_lex;
/*
Processor of errors caused during Item name resolving, now used only to
hide underlying tables in errors about views (i.e. it substitute some
errors for views)
*/
void (*error_processor)(THD *, void *);
void *error_processor_data;
/**
When TRUE, items are resolved in this context against
SELECT_LEX::item_list, SELECT_lex::group_list and
this->table_list. If FALSE, items are resolved only against
this->table_list.
@see st_select_lex::item_list, st_select_lex::group_list
*/
bool resolve_in_select_list;
/*
Security context of this name resolution context. It's used for views
and is non-zero only if the view is defined with SQL SECURITY DEFINER.
*/
Security_context *security_ctx;
Name_resolution_context()
:outer_context(0), table_list(0), select_lex(0),
error_processor_data(0),
security_ctx(0)
{}
void init()
{
resolve_in_select_list= FALSE;
error_processor= &dummy_error_processor;
first_name_resolution_table= NULL;
last_name_resolution_table= NULL;
}
void resolve_in_table_list_only(TABLE_LIST *tables)
{
table_list= first_name_resolution_table= tables;
resolve_in_select_list= FALSE;
}
void process_error(THD *thd)
{
(*error_processor)(thd, error_processor_data);
}
};
/*
Store and restore the current state of a name resolution context.
*/
class Name_resolution_context_state
{
private:
TABLE_LIST *save_table_list;
TABLE_LIST *save_first_name_resolution_table;
TABLE_LIST *save_next_name_resolution_table;
bool save_resolve_in_select_list;
TABLE_LIST *save_next_local;
public:
Name_resolution_context_state() {} /* Remove gcc warning */
public:
/* Save the state of a name resolution context. */
void save_state(Name_resolution_context *context, TABLE_LIST *table_list)
{
save_table_list= context->table_list;
save_first_name_resolution_table= context->first_name_resolution_table;
save_resolve_in_select_list= context->resolve_in_select_list;
save_next_local= table_list->next_local;
save_next_name_resolution_table= table_list->next_name_resolution_table;
}
/* Restore a name resolution context from saved state. */
void restore_state(Name_resolution_context *context, TABLE_LIST *table_list)
{
table_list->next_local= save_next_local;
table_list->next_name_resolution_table= save_next_name_resolution_table;
context->table_list= save_table_list;
context->first_name_resolution_table= save_first_name_resolution_table;
context->resolve_in_select_list= save_resolve_in_select_list;
}
TABLE_LIST *get_first_name_resolution_table()
{
return save_first_name_resolution_table;
}
};
/*
This enum is used to report information about monotonicity of function
represented by Item* tree.
Monotonicity is defined only for Item* trees that represent table
partitioning expressions (i.e. have no subselects/user vars/PS parameters
etc etc). An Item* tree is assumed to have the same monotonicity properties
as its correspoinding function F:
[signed] longlong F(field1, field2, ...) {
put values of field_i into table record buffer;
return item->val_int();
}
NOTE
At the moment function monotonicity is not well defined (and so may be
incorrect) for Item trees with parameters/return types that are different
from INT_RESULT, may be NULL, or are unsigned.
It will be possible to address this issue once the related partitioning bugs
(BUG#16002, BUG#15447, BUG#13436) are fixed.
The NOT_NULL enums are used in TO_DAYS, since TO_DAYS('2001-00-00') returns
NULL which puts those rows into the NULL partition, but
'2000-12-31' < '2001-00-00' < '2001-01-01'. So special handling is needed
for this (see Bug#20577).
*/
typedef enum monotonicity_info
{
NON_MONOTONIC, /* none of the below holds */
MONOTONIC_INCREASING, /* F() is unary and (x < y) => (F(x) <= F(y)) */
MONOTONIC_INCREASING_NOT_NULL, /* But only for valid/real x and y */
MONOTONIC_STRICT_INCREASING,/* F() is unary and (x < y) => (F(x) < F(y)) */
MONOTONIC_STRICT_INCREASING_NOT_NULL /* But only for valid/real x and y */
} enum_monotonicity_info;
/*************************************************************************/
class sp_rcontext;
class Settable_routine_parameter
{
public:
/*
Set required privileges for accessing the parameter.
SYNOPSIS
set_required_privilege()
rw if 'rw' is true then we are going to read and set the
parameter, so SELECT and UPDATE privileges might be
required, otherwise we only reading it and SELECT
privilege might be required.
*/
Settable_routine_parameter() {}
virtual ~Settable_routine_parameter() {}
virtual void set_required_privilege(bool rw) {};
/*
Set parameter value.
SYNOPSIS
set_value()
thd thread handle
ctx context to which parameter belongs (if it is local
variable).
it item which represents new value
RETURN
FALSE if parameter value has been set,
TRUE if error has occured.
*/
virtual bool set_value(THD *thd, sp_rcontext *ctx, Item **it)= 0;
virtual void set_out_param_info(Send_field *info) {}
virtual const Send_field *get_out_param_info() const
{ return NULL; }
};
typedef bool (Item::*Item_processor) (uchar *arg);
/*
Analyzer function
SYNOPSIS
argp in/out IN: Analysis parameter
OUT: Parameter to be passed to the transformer
RETURN
TRUE Invoke the transformer
FALSE Don't do it
*/
typedef bool (Item::*Item_analyzer) (uchar **argp);
typedef Item* (Item::*Item_transformer) (uchar *arg);
typedef void (*Cond_traverser) (const Item *item, void *arg);
class Item
{
Item(const Item &); /* Prevent use of these */
void operator=(Item &);
/* Cache of the result of is_expensive(). */
int8 is_expensive_cache;
virtual bool is_expensive_processor(uchar *arg) { return 0; }
public:
static void *operator new(size_t size) throw ()
{ return sql_alloc(size); }
static void *operator new(size_t size, MEM_ROOT *mem_root) throw ()
{ return alloc_root(mem_root, size); }
static void operator delete(void *ptr,size_t size) { TRASH(ptr, size); }
static void operator delete(void *ptr, MEM_ROOT *mem_root) {}
enum Type {FIELD_ITEM= 0, FUNC_ITEM, SUM_FUNC_ITEM, STRING_ITEM,
INT_ITEM, REAL_ITEM, NULL_ITEM, VARBIN_ITEM,
COPY_STR_ITEM, FIELD_AVG_ITEM, DEFAULT_VALUE_ITEM,
PROC_ITEM,COND_ITEM, REF_ITEM, FIELD_STD_ITEM,
FIELD_VARIANCE_ITEM, INSERT_VALUE_ITEM,
SUBSELECT_ITEM, ROW_ITEM, CACHE_ITEM, TYPE_HOLDER,
PARAM_ITEM, TRIGGER_FIELD_ITEM, DECIMAL_ITEM,
XPATH_NODESET, XPATH_NODESET_CMP,
VIEW_FIXER_ITEM};
enum cond_result { COND_UNDEF,COND_OK,COND_TRUE,COND_FALSE };
enum traverse_order { POSTFIX, PREFIX };
/* Reuse size, only used by SP local variable assignment, otherwize 0 */
uint rsize;
/*
str_values's main purpose is to be used to cache the value in
save_in_field
*/
String str_value;
Item_name_string item_name; /* Name from select */
Item_name_string orig_name; /* Original item name (if it was renamed)*/
/**
Intrusive list pointer for free list. If not null, points to the next
Item on some Query_arena's free list. For instance, stored procedures
have their own Query_arena's.
@see Query_arena::free_list
*/
Item *next;
uint32 max_length; /* Maximum length, in bytes */
/**
This member has several successive meanings, depending on the phase we're
in:
- during field resolution: it contains the index, in the "all_fields"
list, of the expression to which this field belongs; or a special
constant UNDEF_POS; see st_select_lex::cur_pos_in_all_fields and
match_exprs_for_only_full_group_by().
- when attaching conditions to tables: it says whether some condition
needs to be attached or can be omitted (for example because it is already
implemented by 'ref' access)
- when pushing index conditions: it says whether a condition uses only
indexed columns
- when creating an internal temporary table: it says how to store BIT
fields
- when we change DISTINCT to GROUP BY: it is used for book-keeping of
fields.
*/
int marker;
uint8 decimals;
my_bool maybe_null; /* If item may be null */
my_bool null_value; /* if item is null */
my_bool unsigned_flag;
my_bool with_sum_func;
my_bool fixed; /* If item fixed with fix_fields */
DTCollation collation;
Item_result cmp_context; /* Comparison context */
protected:
my_bool with_subselect; /* If this item is a subselect or some
of its arguments is or contains a
subselect. Computed by fix_fields
and updated by update_used_tables. */
my_bool with_stored_program; /* If this item is a stored program
or some of its arguments is or
contains a stored program.
Computed by fix_fields and updated
by update_used_tables. */
/**
This variable is a cache of 'Needed tables are locked'. True if either
'No tables locks is needed' or 'Needed tables are locked'.
If tables are used, then it will be set to
current_thd->lex->is_query_tables_locked().
It is used when checking const_item()/can_be_evaluated_now().
*/
bool tables_locked_cache;
public:
// alloc & destruct is done as start of select using sql_alloc
Item();
/*
Constructor used by Item_field, Item_ref & aggregate (sum) functions.
Used for duplicating lists in processing queries with temporary
tables
Also it used for Item_cond_and/Item_cond_or for creating
top AND/OR structure of WHERE clause to protect it of
optimisation changes in prepared statements
*/
Item(THD *thd, Item *item);
virtual ~Item()
{
#ifdef EXTRA_DEBUG
item_name.set(0);
#endif
} /*lint -e1509 */
void rename(char *new_name);
void init_make_field(Send_field *tmp_field,enum enum_field_types type);
virtual void cleanup();
virtual void make_field(Send_field *field);
virtual Field *make_string_field(TABLE *table);
virtual bool fix_fields(THD *, Item **);
/**
Fix after tables have been moved from one select_lex level to the parent
level, e.g by semijoin conversion.
Basically re-calculate all attributes dependent on the tables.
@param parent_select select_lex that tables are moved to.
@param removed_select select_lex that tables are moved away from,
child of parent_select.
*/
virtual void fix_after_pullout(st_select_lex *parent_select,
st_select_lex *removed_select)
{};
/*
should be used in case where we are sure that we do not need
complete fix_fields() procedure.
*/
inline void quick_fix_field() { fixed= 1; }
/* Function returns 1 on overflow and -1 on fatal errors */
type_conversion_status save_in_field_no_warnings(Field *field,
bool no_conversions);
/**
Save a temporal value in packed longlong format into a Field.
Used in optimizer.
@param OUT field The field to set the value to.
@retval 0 On success.
@retval >0 In error.
*/
virtual type_conversion_status save_in_field(Field *field,
bool no_conversions);
virtual void save_org_in_field(Field *field)
{ (void) save_in_field(field, 1); }
virtual type_conversion_status save_safe_in_field(Field *field)
{ return save_in_field(field, 1); }
virtual bool send(Protocol *protocol, String *str);
virtual bool eq(const Item *, bool binary_cmp) const;
virtual Item_result result_type() const { return REAL_RESULT; }
/**
Result type when an item appear in a numeric context.
See Field::numeric_context_result_type() for more comments.
*/
virtual enum Item_result numeric_context_result_type() const
{
if (is_temporal())
return decimals ? DECIMAL_RESULT : INT_RESULT;
if (result_type() == STRING_RESULT)
return REAL_RESULT;
return result_type();
}
/**
Similar to result_type() but makes DATE, DATETIME, TIMESTAMP
pretend to be numbers rather than strings.
*/
inline enum Item_result temporal_with_date_as_number_result_type() const
{
return is_temporal_with_date() ?
(decimals ? DECIMAL_RESULT : INT_RESULT) : result_type();
}
virtual Item_result cast_to_int_type() const { return result_type(); }
virtual enum_field_types string_field_type() const;
virtual enum_field_types field_type() const;
virtual enum Type type() const =0;
/*
Return information about function monotonicity. See comment for
enum_monotonicity_info for details. This function can only be called
after fix_fields() call.
*/
virtual enum_monotonicity_info get_monotonicity_info() const
{ return NON_MONOTONIC; }
/*
Convert "func_arg $CMP$ const" half-interval into "FUNC(func_arg) $CMP2$ const2"
SYNOPSIS
val_int_endpoint()
left_endp FALSE <=> The interval is "x < const" or "x <= const"
TRUE <=> The interval is "x > const" or "x >= const"
incl_endp IN FALSE <=> the comparison is '<' or '>'
TRUE <=> the comparison is '<=' or '>='
OUT The same but for the "F(x) $CMP$ F(const)" comparison
DESCRIPTION
This function is defined only for unary monotonic functions. The caller
supplies the source half-interval
x $CMP$ const
The value of const is supplied implicitly as the value this item's
argument, the form of $CMP$ comparison is specified through the
function's arguments. The calle returns the result interval
F(x) $CMP2$ F(const)
passing back F(const) as the return value, and the form of $CMP2$
through the out parameter. NULL values are assumed to be comparable and
be less than any non-NULL values.
RETURN
The output range bound, which equal to the value of val_int()
- If the value of the function is NULL then the bound is the
smallest possible value of LONGLONG_MIN
*/
virtual longlong val_int_endpoint(bool left_endp, bool *incl_endp)
{ DBUG_ASSERT(0); return 0; }
/* valXXX methods must return NULL or 0 or 0.0 if null_value is set. */
/*
Return double precision floating point representation of item.
SYNOPSIS
val_real()
RETURN
In case of NULL value return 0.0 and set null_value flag to TRUE.
If value is not null null_value flag will be reset to FALSE.
*/
virtual double val_real()=0;
/*
Return integer representation of item.
SYNOPSIS
val_int()
RETURN
In case of NULL value return 0 and set null_value flag to TRUE.
If value is not null null_value flag will be reset to FALSE.
*/
virtual longlong val_int()=0;
/**
Return date value of item in packed longlong format.
*/
virtual longlong val_date_temporal();
/**
Return time value of item in packed longlong format.
*/
virtual longlong val_time_temporal();
/**
Return date or time value of item in packed longlong format,
depending on item field type.
*/
longlong val_temporal_by_field_type()
{
if (field_type() == MYSQL_TYPE_TIME)
return val_time_temporal();
DBUG_ASSERT(is_temporal_with_date());
return val_date_temporal();
}
/**
Get date or time value in packed longlong format.
Before conversion from MYSQL_TIME to packed format,
the MYSQL_TIME value is rounded to "dec" fractional digits.
*/
longlong val_temporal_with_round(enum_field_types type, uint8 dec);
/*
This is just a shortcut to avoid the cast. You should still use
unsigned_flag to check the sign of the item.
*/
inline ulonglong val_uint() { return (ulonglong) val_int(); }
/*
Return string representation of this item object.
SYNOPSIS
val_str()
str an allocated buffer this or any nested Item object can use to
store return value of this method.
NOTE
Buffer passed via argument should only be used if the item itself
doesn't have an own String buffer. In case when the item maintains
it's own string buffer, it's preferable to return it instead to
minimize number of mallocs/memcpys.
The caller of this method can modify returned string, but only in case
when it was allocated on heap, (is_alloced() is true). This allows
the caller to efficiently use a buffer allocated by a child without
having to allocate a buffer of it's own. The buffer, given to
val_str() as argument, belongs to the caller and is later used by the
caller at it's own choosing.
A few implications from the above:
- unless you return a string object which only points to your buffer
but doesn't manages it you should be ready that it will be
modified.
- even for not allocated strings (is_alloced() == false) the caller
can change charset (see Item_func_{typecast/binary}. XXX: is this
a bug?
- still you should try to minimize data copying and return internal
object whenever possible.
RETURN
In case of NULL value return 0 (NULL pointer) and set null_value flag
to TRUE.
If value is not null null_value flag will be reset to FALSE.
*/
virtual String *val_str(String *str)=0;
/*
Returns string representation of this item in ASCII format.
SYNOPSIS
val_str_ascii()
str - similar to val_str();
NOTE
This method is introduced for performance optimization purposes.
1. val_str() result of some Items in string context
depends on @@character_set_results.
@@character_set_results can be set to a "real multibyte" character
set like UCS2, UTF16, UTF32. (We'll use only UTF32 in the examples
below for convenience.)
So the default string result of such functions
in these circumstances is real multi-byte character set, like UTF32.
For example, all numbers in string context
return result in @@character_set_results:
SELECT CONCAT(20010101); -> UTF32
We do sprintf() first (to get ASCII representation)
and then convert to UTF32;
So these kind "data sources" can use ASCII representation
internally, but return multi-byte data only because
@@character_set_results wants so.
Therefore, conversion from ASCII to UTF32 is applied internally.
2. Some other functions need in fact ASCII input.