MySQL 聚集UDF，计算列表中的奇数总和

继吉

 
 技痒之作 -__-
 
 CREATE AGGREGATE FUNCTION oddsum returns INTEGER SONAME "udf_oddsum.so";
　　CREATE TABLE `v1` (
　　`c` int(11) DEFAULT NULL,
　　`id` int(11) NOT NULL,
　　PRIMARY KEY (`id`)
　　) ENGINE=InnoDB DEFAULT CHARSET=utf8;
　　insert into v1 values(1,0), (3,2), (4,4);
　　
　　select sum(c),oddsum(c) from v1;
　　+--------+-----------+
　　| sum(c) | oddsum(c) |
　　+--------+-----------+
　　|      8 |         4 |
　　+--------+-----------+
　　
 

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include <ctype.h>
#include <my_global.h>
#include <my_sys.h>
#include <mysql.h>
my_bool oddsum_init(UDF_INIT *init, UDF_ARGS *args, char *message)
{
if (args->arg_count != 1 || args->arg_type[0] != INT_RESULT) {
return 1;
}
init->ptr = (char *)(malloc(sizeof(longlong)));
bzero((void*)init->ptr, sizeof(longlong));
return 0;
}
void oddsum_add(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)
{
if (!args->args[0])
return;
longlong new_value= *((longlong*)args->args[0]);
if (new_value % 2)
{
longlong *current_sum= (longlong *)initid->ptr;
*current_sum+= new_value;
}
}
void
oddsum_clear(UDF_INIT* initid, char* is_null __attribute__((unused)),
char* message __attribute__((unused)))
{
bzero((void*)initid->ptr, sizeof(longlong));
}
void oddsum_deinit(UDF_INIT *init)
{
if (init->ptr) {
free(init->ptr);
}
}
longlong oddsum(UDF_INIT* initid, UDF_ARGS* args __attribute__((unused)),
char* is_null, char* error __attribute__((unused)))
{
return *(longlong *)initid->ptr;
}