Postgresql中的RRULE解析

Question

目标：根据RRULE字符串（即FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH）和开始时间戳生成一个时间戳列表，每个时间戳表示事件发生。由于这些时间会根据用户的意愿进行更改，postgresql是（1）严格业务逻辑的质量和（2）触发器（当值更改时自动更新行）所必需的

替代解决方案：

我最终使用了plpythonu（postgresql的python语言）。dateutil库有一个很棒的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库libical与Postgresql C扩展连接起来。这需要一个专门的C程序来完成以下操作：（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：编译到对象文件，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/

步骤2：添加要由C&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：

步骤1：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=# 

当前障碍：

C函数使postgresql服务器崩溃。

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);
        }
}

正在与..一起构建。。

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&使用..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。文件记录了参数：

int icalrecurce_expand_recurrence（char*规则，time_t开始，int计数，time_t*数组）

问题：我们如何在不崩溃postgres的情况下让它发挥作用？

Answer 1

显示的代码中有两个明显的与指针相关的缺陷：

第一个：

    *rrule = PG_GETARG_CHAR(0);

在执行的这一点上，rrule是一个未初始化的指针，该指令试图将一个char写入它所指向的随机位置。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，并且它应该被传递为result，而不是此时再次未初始化的*result。

Answer 2

现在您可以将此扩展用于postgresql。

示例用法：

SELECT * FROM
     unnest(
         rrule_get_occurrences('FREQ=WEEKLY;INTERVAL=1;WKST=MO;UNTIL=20200101T045102Z;BYDAY=SA;BYHOUR=10;BYMINUTE=51;BYSECOND=2'::rrule,
             '2019-12-07 10:51:02+00'::timestamp with time zone)
     );
          unnest
 ------------------------
  2019-12-07 10:51:02+00
  2019-12-14 10:51:02+00
  2019-12-21 10:51:02+00
  2019-12-28 10:51:02+00
 (4 rows)