psql按周分表实现

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之前写了一篇按月分表的文章，由于数据量还是比较多，再细分为按周分表。原理是一样的，只不过修改一下分表的规则，因此修改过的触发器类似下面：
1、建立主表

drop table if exists tbl_week;
CREATE TABLE tbl_week
(
  date_key date,
  hour_key smallint
);

2、定义一个函数
输入一个日期时间获取该时间在那一周的周一的日期，比如2018-11-17得到的就是2018-11-12

CREATE OR REPLACE FUNCTION get_week_first_day(in in_date date,out out_date text)
AS $$
DECLARE mon_date date;
BEGIN
  select in_date - (extract (dow from in_date) - 1 || ' day')::interval INTO mon_date;
  SELECT to_char(mon_date, 'YYYY_MM_DD') INTO out_date;
END;
$$
LANGUAGE plpgsql;

3、自动建表触发器

CREATE OR REPLACE FUNCTION tbl_week_trigger()
RETURNS TRIGGER AS $$
DECLARE this_week_first_day_text TEXT;
        next_week_first_day_text TEXT;
        insert_statement TEXT;
BEGIN
  SELECT get_week_first_day(NEW.date_key) INTO this_week_first_day_text;
  SELECT to_char(to_date(this_week_first_day_text,'YYYY-MM-DD') + interval '7 day', 'YYYY-MM-DD') INTO next_week_first_day_text;
  insert_statement := 'INSERT INTO tbl_week_'
                      || this_week_first_day_text||' VALUES ($1.*)';
  EXECUTE insert_statement USING NEW;
  RETURN NULL;
  EXCEPTION
  WHEN UNDEFINED_TABLE
    THEN
      EXECUTE
      'CREATE TABLE IF NOT EXISTS tbl_week_'
      || this_week_first_day_text
      || '(CHECK (date_key >= '''
      || this_week_first_day_text
      || ''' and date_key<'''
      || next_week_first_day_text
      || ''')) INHERITS (tbl_week)';
      RAISE NOTICE 'CREATE NON-EXISTANT TABLE tbl_week_%', this_week_first_day_text;
      EXECUTE
      'CREATE INDEX tbl_week_date_key_'
      || this_week_first_day_text
      || ' ON tbl_week_'
      || this_week_first_day_text
      || '(date_key)';
      EXECUTE insert_statement USING NEW;
      RETURN NULL;
END;
$$
LANGUAGE plpgsql;

4、挂载分区Trigger

CREATE TRIGGER insert_tbl_week_trigger
    BEFORE INSERT ON tbl_week
    FOR EACH ROW EXECUTE PROCEDURE tbl_week_trigger();

5、分表效果



插入数据后生成了上述一些表，每个表的后缀都是周一的日期。