python – 在Postgresql中解析RRULE
作者：互联网
目标：从RRULE字符串(即FREQ = WEEKLY; INTERVAL = 2; COUNT = 8; WKST = SU; BYDAY = TU,TH)和起始时间戳生成时间戳列表,每个时间戳表示事件发生.
由于这些时间会随着用户的想法而改变,因此需要postgresql(1)严格的业务逻辑质量和(2)触发器(当值发生变化时自动更新行)
替代方案：
我最终使用了plpythonu(postgresql的python语言). dateutil library有一个很棒的rrule解析器.
mydatabase=# CREATE FUNCTION parse_occurrences(rule text, start timestamp) RETURNS timestamp[] AS
mydatabase-# 'from dateutil.rrule import *
mydatabase'# from dateutil.parser import *
mydatabase'# import datetime
mydatabase'# dates = list(rrulestr(rule, dtstart=parse(start)))
mydatabase'# return [str(a)[0:10] for a in dates]'
mydatabase-# LANGUAGE plpythonu;
CREATE FUNCTION
mydatabase=# SELECT parse_occurrences('FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH'::text, now()::timestamp);
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
{"2013-02-14 00:00:00","2013-02-26 00:00:00","2013-02-28 00:00:00","2013-03-12 00:00:00","2013-03-14 00:00:00","2013-03-26 00:00:00","2013-03-28 00:00:00","2013-04-09 00:00:00"}
(原始)努力：将C-library libical连接到Postgresql C-Extensions.这需要专门的C程序来执行以下操作：(1)将postgresql数据类型转换为C数据类型,(2)执行所有必要的C库函数,以及( 3)使用头文件“postgres.h”以postgresql格式返回数据.
连接器文件：ical_recur.c
#include "postgres.h"
#include "icalrecur.h"
#include <time.h> /* for time() */
#include "fmgr.h"
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
PG_FUNCTION_INFO_V1(get_occurrences);
Datum
get_occurrences(PG_FUNCTION_ARGS)
{
//char* rule; /* rule string */
time_t start; /* start time */
int count;
char *rrule;
// *rule = PG_GETARG_CHAR(0);
start = (time_t) PG_GETARG_INT32(1);
count = (int) PG_GETARG_INT32(2);
*rrule = PG_GETARG_CHAR(0);
time_t *result[count]; /* output array */
icalrecur_expand_recurrence(rrule, start, count, *result);
PG_RETURN_INT32(*result);
}
准备连接器文件：
步骤1：编译到目标文件,创建共享对象,复制到postgresql查找C-extensions的位置
sudo gcc -I/usr/local/libical/lib -lical -I/usr/include/postgresql/9.2/server -fpic -c ical_recur.c
sudo gcc -shared -L/usr/local/libical/lib -lical -o ical_recur.so ical_recur.o
sudo cp ical_recur.so /usr/lib/postgresql/9.2/lib/
第2步：添加由C& C找到的libical lib文件夹.重新加载配置
sudo echo "/usr/local/libical/lib" >> /etc/ld.so.conf.d/libc.conf
sudo ldconfig
测试连接器文件：
第1步：加载psql并创建FUNCTION
psql
mydatabase=# CREATE FUNCTION get_occurrences(text, integer, integer) RETURNS int[]
mydatabase=- AS '$libdir/ical_recur', 'get_occurrences'
mydatabase=- LANGUAGE C STRICT;
CREATE FUNCTION
mydatabase=#
目前的路障：
C函数崩溃了postgresql服务器.
psql (9.2.3)
Type "help" for help.
mydatabase=# SELECT get_occurrences('FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH', now()::timestamp, 5);
The connection to the server was lost. Attempting reset: Failed.
!>
日志……
2013-02-11 22:03:33 UTC LOG: server process (PID 22733) was terminated by signal 11: Segmentation fault
2013-02-11 22:03:33 UTC DETAIL: Failed process was running: SELECT get_occurrences('FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH', now()::timestamp, 5);
2013-02-11 22:03:33 UTC LOG: terminating any other active server processes
2013-02-11 22:03:33 UTC WARNING: terminating connection because of crash of another server process
2013-02-11 22:03:33 UTC DETAIL: The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
2013-02-11 22:03:33 UTC HINT: In a moment you should be able to reconnect to the database and repeat your command.
2013-02-11 22:03:33 UTC LOG: all server processes terminated; reinitializing
2013-02-11 22:03:33 UTC FATAL: the database system is in recovery mode
2013-02-11 22:03:33 UTC LOG: database system was interrupted; last known up at 2013-02-11 21:47:26 UTC
2013-02-11 22:03:33 UTC LOG: database system was not properly shut down; automatic recovery in progress
2013-02-11 22:03:33 UTC LOG: redo starts at 0/1903A0C
2013-02-11 22:03:33 UTC LOG: record with zero length at 0/190E1E0
2013-02-11 22:03:33 UTC LOG: redo done at 0/190E1B8
2013-02-11 22:03:33 UTC LOG: last completed transaction was at log time 2013-02-11 22:03:29.641161+00
2013-02-11 22:03:33 UTC LOG: database system is ready to accept connections
2013-02-11 22:03:33 UTC LOG: autovacuum launcher started
更新：
我已经更新了方法以解决一些建议.
#include "postgres.h"
#include "icalrecur.h"
#include <time.h> /* for time() */
#include "fmgr.h"
#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif
PG_FUNCTION_INFO_V1(get_occurrences);
Datum
get_occurrences(PG_FUNCTION_ARGS)
{
time_t start = (time_t) PG_GETARG_INT32(1); /* convert int to time_t */
int count = PG_GETARG_INT32(2);
char rrule = PG_GETARG_CHAR(0);
char *_rrule = &rrule; /* icalrecur wants a pointer to the rrule */
time_t result[count]; /* instantiate the output array */
int success = icalrecur_expand_recurrence(_rrule, start, count, result);
/* convert time_t values to int */
int *output = malloc(sizeof(result));
int i;
for(i = 0; i < (int) (sizeof(result) / sizeof(result[0]) - 1); i++){
output[i] = (int) result[i];
}
if(success != 1){
PG_RETURN_INT32(0);
} else {
PG_RETURN_INT32(output);
}
}
建筑用..
sudo gcc -Wall -Wextra -l/usr/local/libical/lib/ical -I/usr/local/libical/include/libical -I/usr/include/postgresql/9.2/server -fpic -c ical_recur.c
sudo gcc -Wall -shared -static -L/usr/local/libical/lib -lical -o ical_recur.so ical_recur.o
sudo cp libical.so /usr/lib/postgresql/9.2/lib/
输入数据库&执行…
mydb=# CREATE FUNCTION get_occurrences(text, integer, integer) RETURNS int[]
AS '$libdir/ical_recur', 'get_occurrences'
LANGUAGE C STRICT;
CREATE FUNCTION
mydb=# SELECT get_occurrences('FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH', 1360690024, 5);
The connection to the server was lost. Attempting reset: Failed.
!> \q
相同的日志输出. documentation注意到参数：
int icalrecur_expand_recurrence(char * rule, time_t start, int count, time_t * array)
问题：如果没有postgres崩溃,我们怎样才能让它工作？
解决方法:
显示的代码中有两个明显的与指针相关的缺陷：
第一：
*rrule = PG_GETARG_CHAR(0);
在此执行点,rrule是一个非初始化指针,该指令尝试将char写入它指向的随机位置.这通常会导致您看到的那种崩溃.
第二：
time_t *result[count]; /* output array */
icalrecur_expand_recurrence(rrule, start, count, *result);
result应该是time_t的数组,而不是time_t *的数组,它应该作为结果传递,而不是*结果,此时再次没有初始化.
标签：python,postgresql,icalendar,rrule,libical 来源： https://codeday.me/bug/20190901/1781833.html