Aggregator_simple Class Reference

The pass-through aggregator. More...

#include <item_sum.h>

Inheritance diagram for Aggregator_simple:

Public Member Functions
	Aggregator_simple (Item_sum *sum)
Aggregator_type	Aggrtype () override
bool	setup (THD *thd) override
	Called before adding the first row. More...
void	clear () override
	Called when we need to wipe out all the data from the aggregator: all the values accumulated and all the state. More...
bool	add () override
	Called when there's a new value to be aggregated. More...
void	endup () override
	Called when there are no more data and the final value is to be retrieved. More...
my_decimal *	arg_val_decimal (my_decimal *value) override
	Decimal value of being-aggregated argument. More...
double	arg_val_real () override
	Floating point value of being-aggregated argument. More...
bool	arg_is_null (bool use_null_value) override
	NULLness of being-aggregated argument. More...
Public Member Functions inherited from Aggregator
	Aggregator (Item_sum *arg)
virtual	~Aggregator ()=default

Additional Inherited Members
Public Types inherited from Aggregator
enum	Aggregator_type { SIMPLE_AGGREGATOR , DISTINCT_AGGREGATOR }
Protected Attributes inherited from Aggregator
Item_sum *	item_sum

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.

Constructor & Destructor Documentation

Aggregator_simple()

Aggregator_simple::Aggregator_simple ( Item_sum *  sum )

inline

Member Function Documentation

add()

bool Aggregator_simple::add ( )

inlineoverridevirtual

Called when there's a new value to be aggregated.

Updates the internal state of the aggregator to reflect the new value.

Implements Aggregator.

Aggrtype()

Aggregator_type Aggregator_simple::Aggrtype ( )

inlineoverridevirtual

Implements Aggregator.

arg_is_null()

bool Aggregator_simple::arg_is_null ( bool  use_null_value )

overridevirtual

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.

arg_val_decimal()

my_decimal * Aggregator_simple::arg_val_decimal ( my_decimal *  value )

overridevirtual

Decimal value of being-aggregated argument.

Implements Aggregator.

arg_val_real()

double Aggregator_simple::arg_val_real ( )

overridevirtual

Floating point value of being-aggregated argument.

Implements Aggregator.

clear()

void Aggregator_simple::clear ( )

inlineoverridevirtual

Called when we need to wipe out all the data from the aggregator: all the values accumulated and all the state.

Cleans up the internal structures and resets them to their initial state.

Implements Aggregator.

endup()

void Aggregator_simple::endup ( )

inlineoverridevirtual

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.

setup()

bool Aggregator_simple::setup ( THD *  )

inlineoverridevirtual

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:

• sql/item_sum.h
• sql/item_sum.cc