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item_cmpfunc.cc
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item_cmpfunc.cc
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/* Copyright (c) 2000, 2013, 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 */
/**
@file
@brief
This file defines all compare functions
*/
#include "sql_priv.h"
#include <m_ctype.h>
#include "sql_select.h"
#include "sql_optimizer.h" // JOIN_TAB
#include "sql_parse.h" // check_stack_overrun
#include "sql_time.h" // make_truncated_value_warning
#include <algorithm>
using std::min;
using std::max;
static bool convert_constant_item(THD *, Item_field *, Item **);
static longlong
get_year_value(THD *thd, Item ***item_arg, Item **cache_arg,
Item *warn_item, bool *is_null);
static Item_result item_store_type(Item_result a, Item *item,
my_bool unsigned_flag)
{
Item_result b= item->result_type();
if (a == STRING_RESULT || b == STRING_RESULT)
return STRING_RESULT;
else if (a == REAL_RESULT || b == REAL_RESULT)
return REAL_RESULT;
else if (a == DECIMAL_RESULT || b == DECIMAL_RESULT ||
unsigned_flag != item->unsigned_flag)
return DECIMAL_RESULT;
else
return INT_RESULT;
}
static void agg_result_type(Item_result *type, Item **items, uint nitems)
{
Item **item, **item_end;
my_bool unsigned_flag= 0;
*type= STRING_RESULT;
/* Skip beginning NULL items */
for (item= items, item_end= item + nitems; item < item_end; item++)
{
if ((*item)->type() != Item::NULL_ITEM)
{
*type= (*item)->result_type();
unsigned_flag= (*item)->unsigned_flag;
item++;
break;
}
}
/* Combine result types. Note: NULL items don't affect the result */
for (; item < item_end; item++)
{
if ((*item)->type() != Item::NULL_ITEM)
*type= item_store_type(*type, *item, unsigned_flag);
}
}
/*
Compare row signature of two expressions
SYNOPSIS:
cmp_row_type()
item1 the first expression
item2 the second expression
DESCRIPTION
The function checks that two expressions have compatible row signatures
i.e. that the number of columns they return are the same and that if they
are both row expressions then each component from the first expression has
a row signature compatible with the signature of the corresponding component
of the second expression.
RETURN VALUES
1 type incompatibility has been detected
0 otherwise
*/
static int cmp_row_type(Item* item1, Item* item2)
{
uint n= item1->cols();
if (item2->check_cols(n))
return 1;
for (uint i=0; i<n; i++)
{
if (item2->element_index(i)->check_cols(item1->element_index(i)->cols()) ||
(item1->element_index(i)->result_type() == ROW_RESULT &&
cmp_row_type(item1->element_index(i), item2->element_index(i))))
return 1;
}
return 0;
}
/**
Aggregates result types from the array of items.
SYNOPSIS:
agg_cmp_type()
type [out] the aggregated type
items array of items to aggregate the type from
nitems number of items in the array
DESCRIPTION
This function aggregates result types from the array of items. Found type
supposed to be used later for comparison of values of these items.
Aggregation itself is performed by the item_cmp_type() function.
@param[out] type the aggregated type
@param items array of items to aggregate the type from
@param nitems number of items in the array
@retval
1 type incompatibility has been detected
@retval
0 otherwise
*/
static int agg_cmp_type(Item_result *type, Item **items, uint nitems)
{
uint i;
type[0]= items[0]->result_type();
for (i= 1 ; i < nitems ; i++)
{
type[0]= item_cmp_type(type[0], items[i]->result_type());
/*
When aggregating types of two row expressions we have to check
that they have the same cardinality and that each component
of the first row expression has a compatible row signature with
the signature of the corresponding component of the second row
expression.
*/
if (type[0] == ROW_RESULT && cmp_row_type(items[0], items[i]))
return 1; // error found: invalid usage of rows
}
return 0;
}
/**
@brief Aggregates field types from the array of items.
@param[in] items array of items to aggregate the type from
@paran[in] nitems number of items in the array
@details This function aggregates field types from the array of items.
Found type is supposed to be used later as the result field type
of a multi-argument function.
Aggregation itself is performed by the Field::field_type_merge()
function.
@note The term "aggregation" is used here in the sense of inferring the
result type of a function from its argument types.
@return aggregated field type.
*/
enum_field_types agg_field_type(Item **items, uint nitems)
{
uint i;
if (!nitems || items[0]->result_type() == ROW_RESULT )
return (enum_field_types)-1;
enum_field_types res= items[0]->field_type();
for (i= 1 ; i < nitems ; i++)
res= Field::field_type_merge(res, items[i]->field_type());
return real_type_to_type(res);
}
/*
Collects different types for comparison of first item with each other items
SYNOPSIS
collect_cmp_types()
items Array of items to collect types from
nitems Number of items in the array
skip_nulls Don't collect types of NULL items if TRUE
DESCRIPTION
This function collects different result types for comparison of the first
item in the list with each of the remaining items in the 'items' array.
RETURN
0 - if row type incompatibility has been detected (see cmp_row_type)
Bitmap of collected types - otherwise
*/
static uint collect_cmp_types(Item **items, uint nitems, bool skip_nulls= FALSE)
{
uint i;
uint found_types;
Item_result left_result= items[0]->result_type();
DBUG_ASSERT(nitems > 1);
found_types= 0;
for (i= 1; i < nitems ; i++)
{
if (skip_nulls && items[i]->type() == Item::NULL_ITEM)
continue; // Skip NULL constant items
if ((left_result == ROW_RESULT ||
items[i]->result_type() == ROW_RESULT) &&
cmp_row_type(items[0], items[i]))
return 0;
found_types|= 1U << (uint)item_cmp_type(left_result,
items[i]->result_type());
}
/*
Even if all right-hand items are NULLs and we are skipping them all, we need
at least one type bit in the found_type bitmask.
*/
if (skip_nulls && !found_types)
found_types= 1U << (uint)left_result;
return found_types;
}
static void my_coll_agg_error(DTCollation &c1, DTCollation &c2,
const char *fname)
{
my_error(ER_CANT_AGGREGATE_2COLLATIONS, MYF(0),
c1.collation->name,c1.derivation_name(),
c2.collation->name,c2.derivation_name(),
fname);
}
Item_bool_func2* Eq_creator::create(Item *a, Item *b) const
{
return new Item_func_eq(a, b);
}
Item_bool_func2* Ne_creator::create(Item *a, Item *b) const
{
return new Item_func_ne(a, b);
}
Item_bool_func2* Gt_creator::create(Item *a, Item *b) const
{
return new Item_func_gt(a, b);
}
Item_bool_func2* Lt_creator::create(Item *a, Item *b) const
{
return new Item_func_lt(a, b);
}
Item_bool_func2* Ge_creator::create(Item *a, Item *b) const
{
return new Item_func_ge(a, b);
}
Item_bool_func2* Le_creator::create(Item *a, Item *b) const
{
return new Item_func_le(a, b);
}
/*
Test functions
Most of these returns 0LL if false and 1LL if true and
NULL if some arg is NULL.
*/
longlong Item_func_not::val_int()
{
DBUG_ASSERT(fixed == 1);
bool value= args[0]->val_bool();
null_value=args[0]->null_value;
return ((!null_value && value == 0) ? 1 : 0);
}
/*
We put any NOT expression into parenthesis to avoid
possible problems with internal view representations where
any '!' is converted to NOT. It may cause a problem if
'!' is used in an expression together with other operators
whose precedence is lower than the precedence of '!' yet
higher than the precedence of NOT.
*/
void Item_func_not::print(String *str, enum_query_type query_type)
{
str->append('(');
Item_func::print(str, query_type);
str->append(')');
}
/**
special NOT for ALL subquery.
*/
longlong Item_func_not_all::val_int()
{
DBUG_ASSERT(fixed == 1);
bool value= args[0]->val_bool();
/*
return TRUE if there was records in underlying select in max/min
optimization (ALL subquery)
*/
if (empty_underlying_subquery())
return 1;
null_value= args[0]->null_value;
return ((!null_value && value == 0) ? 1 : 0);
}
bool Item_func_not_all::empty_underlying_subquery()
{
DBUG_ASSERT(subselect || !(test_sum_item || test_sub_item));
/*
When outer argument is NULL the subquery has not yet been evaluated, we
need to evaluate it to get to know whether it returns any rows to return
the correct result. 'ANY' subqueries are an exception because the
result would be false or null which for a top level item always mean false.
The subselect->unit->item->... chain should be used instead of
subselect->... to workaround subquery transformation which could make
subselect->engine unusable.
*/
if (subselect &&
subselect->substype() != Item_subselect::ANY_SUBS &&
!subselect->unit->item->is_evaluated())
subselect->unit->item->exec();
return ((test_sum_item && !test_sum_item->any_value()) ||
(test_sub_item && !test_sub_item->any_value()));
}
void Item_func_not_all::print(String *str, enum_query_type query_type)
{
if (show)
Item_func::print(str, query_type);
else
args[0]->print(str, query_type);
}
/**
Special NOP (No OPeration) for ALL subquery. It is like
Item_func_not_all.
@return
(return TRUE if underlying subquery do not return rows) but if subquery
returns some rows it return same value as argument (TRUE/FALSE).
*/
longlong Item_func_nop_all::val_int()
{
DBUG_ASSERT(fixed == 1);
longlong value= args[0]->val_int();
/*
return FALSE if there was records in underlying select in max/min
optimization (SAME/ANY subquery)
*/
if (empty_underlying_subquery())
return 0;
null_value= args[0]->null_value;
return (null_value || value == 0) ? 0 : 1;
}
/**
Convert a constant item to an int and replace the original item.
The function converts a constant expression or string to an integer.
On successful conversion the original item is substituted for the
result of the item evaluation.
This is done when comparing DATE/TIME of different formats and
also when comparing bigint to strings (in which case strings
are converted to bigints).
@param thd thread handle
@param field item will be converted using the type of this field
@param[in,out] item reference to the item to convert
@note
This function is called only at prepare stage.
As all derived tables are filled only after all derived tables
are prepared we do not evaluate items with subselects here because
they can contain derived tables and thus we may attempt to use a
table that has not been populated yet.
@retval
0 Can't convert item
@retval
1 Item was replaced with an integer version of the item
*/
static bool convert_constant_item(THD *thd, Item_field *field_item,
Item **item)
{
Field *field= field_item->field;
int result= 0;
if ((*item)->const_item())
{
TABLE *table= field->table;
sql_mode_t orig_sql_mode= thd->variables.sql_mode;
enum_check_fields orig_count_cuted_fields= thd->count_cuted_fields;
my_bitmap_map *old_maps[2];
ulonglong UNINIT_VAR(orig_field_val); /* original field value if valid */
LINT_INIT(old_maps[0]);
LINT_INIT(old_maps[1]);
if (table)
dbug_tmp_use_all_columns(table, old_maps,
table->read_set, table->write_set);
/* For comparison purposes allow invalid dates like 2000-01-32 */
thd->variables.sql_mode= (orig_sql_mode & ~MODE_NO_ZERO_DATE) |
MODE_INVALID_DATES;
thd->count_cuted_fields= CHECK_FIELD_IGNORE;
/*
Store the value of the field/constant if it references an outer field
because the call to save_in_field below overrides that value.
Don't save field value if no data has been read yet.
Outer constant values are always saved.
*/
bool save_field_value= (field_item->depended_from &&
(field_item->const_item() ||
!(field->table->status &
(STATUS_GARBAGE | STATUS_NOT_FOUND))));
if (save_field_value)
orig_field_val= field->val_int();
int rc;
if (!(*item)->is_null() &&
(((rc= (*item)->save_in_field(field, 1)) == TYPE_OK) ||
rc == TYPE_NOTE_TIME_TRUNCATED)) // TS-TODO
{
int field_cmp= 0;
/*
If item is a decimal value, we must reject it if it was truncated.
TODO: consider doing the same for MYSQL_TYPE_YEAR,.
However: we have tests which assume that things '1999' and
'1991-01-01 01:01:01' can be converted to year.
Testing for MYSQL_TYPE_YEAR here, would treat such literals
as 'incorrect DOUBLE value'.
See Bug#13580652 YEAR COLUMN CAN BE EQUAL TO 1999.1
*/
if (field->type() == MYSQL_TYPE_LONGLONG)
{
field_cmp= stored_field_cmp_to_item(thd, field, *item);
DBUG_PRINT("info", ("convert_constant_item %d", field_cmp));
}
if (0 == field_cmp)
{
Item *tmp= field->type() == MYSQL_TYPE_TIME ?
#define OLD_CMP
#ifdef OLD_CMP
new Item_time_with_ref(field->decimals(),
field->val_time_temporal(), *item) :
#else
new Item_time_with_ref(max((*item)->time_precision(),
field->decimals()),
(*item)->val_time_temporal(),
*item) :
#endif
field->is_temporal_with_date() ?
#ifdef OLD_CMP
new Item_datetime_with_ref(field->type(),
field->decimals(),
field->val_date_temporal(),
*item) :
#else
new Item_datetime_with_ref(field->type(),
max((*item)->datetime_precision(),
field->decimals()),
(*item)->val_date_temporal(),
*item) :
#endif
new Item_int_with_ref(field->val_int(), *item,
MY_TEST(field->flags & UNSIGNED_FLAG));
if (tmp)
thd->change_item_tree(item, tmp);
result= 1; // Item was replaced
}
}
/* Restore the original field value. */
if (save_field_value)
{
result= field->store(orig_field_val, TRUE);
/* orig_field_val must be a valid value that can be restored back. */
DBUG_ASSERT(!result);
}
thd->variables.sql_mode= orig_sql_mode;
thd->count_cuted_fields= orig_count_cuted_fields;
if (table)
dbug_tmp_restore_column_maps(table->read_set, table->write_set, old_maps);
}
return result;
}
bool Item_bool_func2::convert_constant_arg(THD *thd, Item *field, Item **item)
{
if (field->real_item()->type() != FIELD_ITEM)
return false;
Item_field *field_item= (Item_field*) (field->real_item());
if (field_item->field->can_be_compared_as_longlong() &&
!(field_item->is_temporal_with_date() &&
(*item)->result_type() == STRING_RESULT))
{
if (convert_constant_item(thd, field_item, item))
{
cmp.set_cmp_func(this, tmp_arg, tmp_arg + 1, INT_RESULT);
field->cmp_context= (*item)->cmp_context= INT_RESULT;
return true;
}
}
return false;
}
void Item_bool_func2::fix_length_and_dec()
{
max_length= 1; // Function returns 0 or 1
THD *thd;
/*
As some compare functions are generated after sql_yacc,
we have to check for out of memory conditions here
*/
if (!args[0] || !args[1])
return;
DBUG_ENTER("Item_bool_func2::fix_length_and_dec");
/*
See agg_item_charsets() in item.cc for comments
on character set and collation aggregation.
*/
if (args[0]->result_type() == STRING_RESULT &&
args[1]->result_type() == STRING_RESULT &&
agg_arg_charsets_for_comparison(cmp.cmp_collation, args, 2))
DBUG_VOID_RETURN;
args[0]->cmp_context= args[1]->cmp_context=
item_cmp_type(args[0]->result_type(), args[1]->result_type());
// Make a special case of compare with fields to get nicer DATE comparisons
if (functype() == LIKE_FUNC) // Disable conversion in case of LIKE function.
{
set_cmp_func();
DBUG_VOID_RETURN;
}
thd= current_thd;
if (!thd->lex->is_ps_or_view_context_analysis())
{
if (convert_constant_arg(thd, args[0], &args[1]) ||
convert_constant_arg(thd, args[1], &args[0]))
DBUG_VOID_RETURN;
}
set_cmp_func();
DBUG_VOID_RETURN;
}
int Arg_comparator::set_compare_func(Item_result_field *item, Item_result type)
{
owner= item;
func= comparator_matrix[type]
[is_owner_equal_func()];
switch (type) {
case ROW_RESULT:
{
uint n= (*a)->cols();
if (n != (*b)->cols())
{
my_error(ER_OPERAND_COLUMNS, MYF(0), n);
comparators= 0;
return 1;
}
if (!(comparators= new Arg_comparator[n]))
return 1;
for (uint i=0; i < n; i++)
{
if ((*a)->element_index(i)->cols() != (*b)->element_index(i)->cols())
{
my_error(ER_OPERAND_COLUMNS, MYF(0), (*a)->element_index(i)->cols());
return 1;
}
if (comparators[i].set_cmp_func(owner, (*a)->addr(i), (*b)->addr(i),
set_null))
return 1;
}
break;
}
case STRING_RESULT:
{
/*
We must set cmp_charset here as we may be called from for an automatic
generated item, like in natural join
*/
if (cmp_collation.set((*a)->collation, (*b)->collation) ||
cmp_collation.derivation == DERIVATION_NONE)
{
my_coll_agg_error((*a)->collation, (*b)->collation,
owner->func_name());
return 1;
}
if (cmp_collation.collation == &my_charset_bin)
{
/*
We are using BLOB/BINARY/VARBINARY, change to compare byte by byte,
without removing end space
*/
if (func == &Arg_comparator::compare_string)
func= &Arg_comparator::compare_binary_string;
else if (func == &Arg_comparator::compare_e_string)
func= &Arg_comparator::compare_e_binary_string;
/*
As this is binary compassion, mark all fields that they can't be
transformed. Otherwise we would get into trouble with comparisons
like:
WHERE col= 'j' AND col LIKE BINARY 'j'
which would be transformed to:
WHERE col= 'j'
*/
(*a)->walk(&Item::set_no_const_sub, FALSE, (uchar*) 0);
(*b)->walk(&Item::set_no_const_sub, FALSE, (uchar*) 0);
}
break;
}
case INT_RESULT:
{
if ((*a)->is_temporal() && (*b)->is_temporal())
{
func= is_owner_equal_func() ?
&Arg_comparator::compare_e_time_packed :
&Arg_comparator::compare_time_packed;
}
else if (func == &Arg_comparator::compare_int_signed)
{
if ((*a)->unsigned_flag)
func= (((*b)->unsigned_flag)?
&Arg_comparator::compare_int_unsigned :
&Arg_comparator::compare_int_unsigned_signed);
else if ((*b)->unsigned_flag)
func= &Arg_comparator::compare_int_signed_unsigned;
}
else if (func== &Arg_comparator::compare_e_int)
{
if ((*a)->unsigned_flag ^ (*b)->unsigned_flag)
func= &Arg_comparator::compare_e_int_diff_signedness;
}
break;
}
case DECIMAL_RESULT:
break;
case REAL_RESULT:
{
if ((*a)->decimals < NOT_FIXED_DEC && (*b)->decimals < NOT_FIXED_DEC)
{
precision= 5 / log_10[max((*a)->decimals, (*b)->decimals) + 1];
if (func == &Arg_comparator::compare_real)
func= &Arg_comparator::compare_real_fixed;
else if (func == &Arg_comparator::compare_e_real)
func= &Arg_comparator::compare_e_real_fixed;
}
break;
}
default:
DBUG_ASSERT(0);
}
return 0;
}
/**
Parse date provided in a string to a MYSQL_TIME.
@param[in] thd Thread handle
@param[in] str A string to convert
@param[in] warn_type Type of the timestamp for issuing the warning
@param[in] warn_name Field name for issuing the warning
@param[out] l_time The MYSQL_TIME objects is initialized.
Parses a date provided in the string str into a MYSQL_TIME object. If the
string contains an incorrect date or doesn't correspond to a date at all
then a warning is issued. The warn_type and the warn_name arguments are used
as the name and the type of the field when issuing the warning. If any input
was discarded (trailing or non-timestamp-y characters), return value will be
TRUE.
@return Status flag
@retval FALSE Success.
@retval True Indicates failure.
*/
bool get_mysql_time_from_str(THD *thd, String *str, timestamp_type warn_type,
const char *warn_name, MYSQL_TIME *l_time)
{
bool value;
MYSQL_TIME_STATUS status;
if (!str_to_datetime(str, l_time,
(TIME_FUZZY_DATE | MODE_INVALID_DATES |
(thd->variables.sql_mode &
(MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE))), &status) &&
(l_time->time_type == MYSQL_TIMESTAMP_DATETIME ||
l_time->time_type == MYSQL_TIMESTAMP_DATE))
/*
Do not return yet, we may still want to throw a "trailing garbage"
warning.
*/
value= FALSE;
else
{
value= TRUE;
status.warnings= MYSQL_TIME_WARN_TRUNCATED; /* force warning */
}
if (status.warnings > 0)
make_truncated_value_warning(thd, Sql_condition::WARN_LEVEL_WARN,
ErrConvString(str), warn_type, warn_name);
return value;
}
/**
@brief Convert date provided in a string
to its packed temporal int representation.
@param[in] thd thread handle
@param[in] str a string to convert
@param[in] warn_type type of the timestamp for issuing the warning
@param[in] warn_name field name for issuing the warning
@param[out] error_arg could not extract a DATE or DATETIME
@details Convert date provided in the string str to the int
representation. If the string contains wrong date or doesn't
contain it at all then a warning is issued. The warn_type and
the warn_name arguments are used as the name and the type of the
field when issuing the warning.
@return
converted value. 0 on error and on zero-dates -- check 'failure'
*/
static ulonglong get_date_from_str(THD *thd, String *str,
timestamp_type warn_type,
const char *warn_name, bool *error_arg)
{
MYSQL_TIME l_time;
*error_arg= get_mysql_time_from_str(thd, str, warn_type, warn_name, &l_time);
if (*error_arg)
return 0;
return TIME_to_longlong_datetime_packed(&l_time);
}
/**
Check if str_arg is a constant and convert it to datetime packed value.
Note, const_value may stay untouched, so the caller is responsible to
initialize it.
@param date_arg - date argument, it's name is used for error reporting.
@param str_arg - string argument to get datetime value from.
@param OUT const_value - the converted value is stored here, if not NULL.
@return true on error, false on success, false if str_arg is not a const.
*/
bool Arg_comparator::get_date_from_const(Item *date_arg,
Item *str_arg,
ulonglong *const_value)
{
THD *thd= current_thd;
/*
Do not cache GET_USER_VAR() function as its const_item() may return TRUE
for the current thread but it still may change during the execution.
Don't use cache while in the context analysis mode only (i.e. for
EXPLAIN/CREATE VIEW and similar queries). Cache is useless in such
cases and can cause problems. For example evaluating subqueries can
confuse storage engines since in context analysis mode tables
aren't locked.
*/
if (!thd->lex->is_ps_or_view_context_analysis() &&
str_arg->const_item() &&
(str_arg->type() != Item::FUNC_ITEM ||
((Item_func*) str_arg)->functype() != Item_func::GUSERVAR_FUNC))
{
ulonglong value;
if (str_arg->field_type() == MYSQL_TYPE_TIME)
{
// Convert from TIME to DATETIME
value= str_arg->val_date_temporal();
if (str_arg->null_value)
return true;
}
else
{
// Convert from string to DATETIME
DBUG_ASSERT(str_arg->result_type() == STRING_RESULT);
bool error;
String tmp, *str_val= 0;
timestamp_type t_type= (date_arg->field_type() == MYSQL_TYPE_DATE ?
MYSQL_TIMESTAMP_DATE : MYSQL_TIMESTAMP_DATETIME);
str_val= str_arg->val_str(&tmp);
if (str_arg->null_value)
return true;
value= get_date_from_str(thd, str_val, t_type,
date_arg->item_name.ptr(), &error);
if (error)
return true;
}
if (const_value)
*const_value= value;
}
return false;
}
/*
Check whether compare_datetime() can be used to compare items.
SYNOPSIS
Arg_comparator::can_compare_as_dates()
a, b [in] items to be compared
const_value [out] converted value of the string constant, if any
DESCRIPTION
Check several cases when the DATE/DATETIME comparator should be used.
The following cases are checked:
1. Both a and b is a DATE/DATETIME field/function returning string or
int result.
2. Only a or b is a DATE/DATETIME field/function returning string or
int result and the other item (b or a) is an item with string result.
If the second item is a constant one then it's checked to be
convertible to the DATE/DATETIME type. If the constant can't be
converted to a DATE/DATETIME then the compare_datetime() comparator
isn't used and the warning about wrong DATE/DATETIME value is issued.
In all other cases (date-[int|real|decimal]/[int|real|decimal]-date)
the comparison is handled by other comparators.
If the datetime comparator can be used and one the operands of the
comparison is a string constant that was successfully converted to a
DATE/DATETIME type then the result of the conversion is returned in the
const_value if it is provided. If there is no constant or
compare_datetime() isn't applicable then the *const_value remains
unchanged.
@return true if can compare as dates, false otherwise.
*/
bool
Arg_comparator::can_compare_as_dates(Item *a, Item *b, ulonglong *const_value)
{
if (a->type() == Item::ROW_ITEM || b->type() == Item::ROW_ITEM)
return false;
if (a->is_temporal_with_date())
{
if (b->is_temporal_with_date()) // date[time] + date
{
return true;
}
else if (b->result_type() == STRING_RESULT) // date[time] + string
{
return !get_date_from_const(a, b, const_value);
}
else
return false; // date[time] + number
}
else if (b->is_temporal_with_date() &&
a->result_type() == STRING_RESULT) // string + date[time]
{
return !get_date_from_const(b, a, const_value);
}
else
return false; // No date[time] items found
}
/*
Retrieves correct TIME value from the given item.
SYNOPSIS
get_time_value()
thd thread handle
item_arg [in/out] item to retrieve TIME value from
cache_arg [in/out] pointer to place to store the cache item to
warn_item [in] unused
is_null [out] TRUE <=> the item_arg is null
DESCRIPTION
Retrieves the correct TIME value from given item for comparison by the
compare_datetime() function.
If item's result can be compared as longlong then its int value is used
and a value returned by get_time function is used otherwise.
If an item is a constant one then its value is cached and it isn't
get parsed again. An Item_cache_int object is used for for cached values.
It seamlessly substitutes the original item. The cache item is marked as
non-constant to prevent re-caching it again.
RETURN
obtained value
*/
longlong
get_time_value(THD *thd, Item ***item_arg, Item **cache_arg,
Item *warn_item, bool *is_null)
{
longlong value;
Item *item= **item_arg;
/*
Note, it's wrong to assume that we always get
a TIME expression or NULL here:
DBUG_ASSERT(item->field_type() == MYSQL_TYPE_TIME ||
item->field_type() == MYSQL_TYPE_NULL);
because when this condition is optimized:
WHERE time_column=DATE(NULL) AND time_column=TIME(NULL);
rhe first AND part is eliminated and DATE(NULL) is substituted
to the second AND part like this:
WHERE DATE(NULL) = TIME(NULL) // as TIME
whose Arg_comparator has already get_time_value set for both arguments.
Therefore, get_time_value is executed for DATE(NULL).
This condition is further evaluated as impossible condition.
TS-TODO: perhaps such cases should be evaluated without
calling get_time_value at all.
See a similar comment in Arg_comparator::compare_time_packed.
*/
value= item->val_time_temporal();
*is_null= item->null_value;
/*
Do not cache GET_USER_VAR() function as its const_item() may return TRUE
for the current thread but it still may change during the execution.
*/
if (item->const_item() && cache_arg &&
item->type() != Item::CACHE_ITEM &&
(item->type() != Item::FUNC_ITEM ||
((Item_func*)item)->functype() != Item_func::GUSERVAR_FUNC))
{
Item_cache_datetime *cache= new Item_cache_datetime(item->field_type());
/* Mark the cache as non-const to prevent re-caching. */
cache->set_used_tables(1);
cache->store(item, value);
*cache_arg= cache;
*item_arg= cache_arg;
}
return value;
}
int Arg_comparator::set_cmp_func(Item_result_field *owner_arg,
Item **a1, Item **a2,
Item_result type)
{
ulonglong const_value= (ulonglong)-1;
thd= current_thd;
owner= owner_arg;
set_null= set_null && owner_arg;
a= a1;
b= a2;
if (can_compare_as_dates(*a, *b, &const_value))
{
a_type= (*a)->field_type();
b_type= (*b)->field_type();
a_cache= 0;