在Postgres存储过程中创建插入查询的字符串数组并执行它们

Question

I have a requirement to construct a string array of all the insert queries with dynamic values being iterated over a cursor.

The procedure looks like this:

CREATE OR REPLACE FUNCTION get_data()
 RETURNS void AS $$
DECLARE
    interval_time INTEGER DEFAULT 0;
    rec_old   RECORD;
    rec_new   RECORD;
    rec_start RECORD;
    v_filename VARCHAR(50);
    querystring TEXT[];

    cursor_file CURSOR FOR
        select distinct(filename) from mytable.tableA;
    cursor_data CURSOR FOR
            select * from mytable.tableA where filename = v_filename order by mindatetime, maxdatetime;
BEGIN
    --open the file cursor
    OPEN cursor_file;
        LOOP
        FETCH cursor_file into v_filename;
        EXIT WHEN NOT FOUND;

            -- Open the second cursor
               OPEN cursor_data;
               FETCH cursor_data INTO rec_old;
               rec_start = rec_old;
               LOOP
                -- fetch each record
                  FETCH cursor_data INTO rec_new;
                      interval_time :=   extract(epoch from rec_new.mindatetime) * 1000 - extract(epoch from rec_old.maxdatetime) * 1000;
                      IF interval_time = 1  THEN
                        -- swap the new and old rec


                        querystring='{insert into mytable.tableA values ('rec_new.fileid,rec_new.systemuid,rec_new.filename,rec_new.mindatetime,rec_new.maxdatetime')}';
                        raise notice 'query is %', querystring;
                        rec_old = rec_new;
                      ELSE
                        -- insert new records to other table
                        RAISE NOTICE 'Values to insert: %, % ', rec_start.mindatetime, rec_old.maxdatetime;


                      END IF;
                      -- exit when no more row to fetch
                      EXIT WHEN NOT FOUND;
               END LOOP;

               -- Close the cursor
               CLOSE cursor_data;

        END LOOP;
    CLOSE cursor_file;
END; $$
LANGUAGE plpgsql;

I need the string array to be like:

{insert into mytable.tableA values ('123','dummyfilenameA','2019-04-21 03:06:26.0','2019-04-28 03:06:26.0'),
insert into mytable.tableA values ('456','dummyfilenameB','2019-05-21 03:06:26.0','2019-05-28 03:06:26.0')}

and so on. The array should use the records data to construct the query. Finally, I want to execute this query string. Is there a way to do this? I can't update the table while iterating over the cursors as its impacting the data already present.

Answer 1

如果您使用函数array_append（anyarray，anyelement）将元素添加到数组querystring？

querystring:=array_append(querystring,'insert...');