Aggregator_simple Class Reference

#include <item_sum.h>

Inheritance diagram for Aggregator_simple:

List of all members.

Public Member Functions
	Aggregator_simple (Item_sum *sum)
Aggregator_type	Aggrtype ()
bool	setup (THD *thd)
void	clear ()
bool	add ()
void	endup ()
virtual my_decimal *	arg_val_decimal (my_decimal *value)
virtual double	arg_val_real ()
virtual bool	arg_is_null (bool use_null_value)

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Detailed Description

The pass-through aggregator. Implements AGGFN (DISTINCT ..) by knowing it gets distinct data on input. So it just pumps them back to the Item_sum descendant class.

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Member Function Documentation

bool Aggregator_simple::add

(

)

[inline, virtual]

Called when there's a new value to be aggregated. Updates the internal state of the aggregator to reflect the new value.

Implements Aggregator.

bool Aggregator_simple::arg_is_null

(

bool

use_null_value

)

[virtual]

NULLness of being-aggregated argument.

Parameters:

use_null_value

Optimization: to determine if the argument is NULL we must, in the general case, call is_null() on it, which itself might call val_*() on it, which might be costly. If you just have called arg_val*(), you can pass use_null_value=true; this way, arg_is_null() might avoid is_null() and instead do a cheap read of the Item's null_value (updated by arg_val*()).

Implements Aggregator.

my_decimal * Aggregator_simple::arg_val_decimal

(

my_decimal *

value

)

[virtual]

Decimal value of being-aggregated argument

Implements Aggregator.

double Aggregator_simple::arg_val_real

(

)

[virtual]

Floating point value of being-aggregated argument

Implements Aggregator.

void Aggregator_simple::clear

(

)

[inline, virtual]

Called when we need to wipe out all the data from the aggregator : all the values acumulated and all the state. Cleans up the internal structures and resets them to their initial state.

Implements Aggregator.

void Aggregator_simple::endup

(

)

[inline, virtual]

Called when there are no more data and the final value is to be retrieved. Finalises the state of the aggregator, so the final result can be retrieved.

Implements Aggregator.

bool Aggregator_simple::setup

(

THD *

)

[inline, virtual]

Called before adding the first row. Allocates and sets up the internal aggregation structures used, e.g. the Unique instance used to calculate distinct.

Implements Aggregator.

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

• item_sum.h
• item_sum.cc