Array error passing dynamic number of parameters to function

Question

I'm trying to create a function to receive the name of the table in my schema already created and a several name of columns within this table (dynamic number of columns) and return a table with all the columns in a unique column with the value of each column separated by comma.

I'm trying this:

CREATE OR REPLACE PROCEDURE public.matching(IN table text, VARIADIC column_names text[])
    LANGUAGE 'plpgsql'

AS $BODY$DECLARE  
    column_text text;
BEGIN
EXECUTE format ($$ SELECT array_to_string(%s, ' ')$$, column_names) into column_text;

EXECUTE format ($$ CREATE TABLE temp1 AS
SELECT concat(%s, ' ') FROM %s $$, column_text, table);

END;$BODY$;

This return an error: ERROR: syntax error at or near «{» LINE 1: SELECT array_to_string({city,address}, ' ')

which is the error?

score 1 · Accepted Answer · 2020-04-15 07:25:05Z

If you simplify the generation of the dynamic SQL, things get easier:

CREATE OR REPLACE PROCEDURE public.matching(IN table_name text, VARIADIC column_names text[])
    LANGUAGE plpgsql
AS 
$BODY$
DECLARE  
  l_sql text;
BEGIN
  l_sql := format($s$
                   create table temp1 as
                   select concat_ws(',', %s) as everything 
                   from %I
                  $s$, array_to_string(column_names, ','), table_name);
  raise notice 'Running %', l_sql;
  EXECUTE l_sql;
END;
$BODY$;

So if you e.g. pass in 'some_table' and {'one', 'two', 'three'} the generated SQL will look like this:

create table temp1 as select concat_ws(',', one,two,three) as everything from some_table

I also used a column alias for the new column, so that the new table has a defined name. Note that the way I put the column names into the SQL string won't properly deal with identifiers that need double quotes (but they should be avoided anyway)

If you want to "return a table", then maybe a function might be the better solution:

CREATE OR REPLACE function matching(IN table_name text, VARIADIC column_names text[])
  returns table (everything text)
  LANGUAGE plpgsql
AS 
$BODY$
DECLARE  
  l_sql text;
BEGIN
  l_sql := format($s$
                   select concat_ws(',', %s) as everything 
                   from %I
                  $s$, array_to_string(column_names, ','), table_name);
  return query execute l_sql;
END;
$BODY$;

Then you can use it like this:

select *
from matching('some_table', 'one', 'two', 'three');

pifor · Accepted Answer · 2020-04-14 11:38:32Z

I propose different but similar code.

With following script:

CREATE OR REPLACE PROCEDURE public.test(IN p_old_table text, IN p_old_column_names text[], IN p_new_table text)
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE  
   old_column_list text;
   ctas_stmt text;
BEGIN
old_column_list = array_to_string(p_old_column_names,',');
RAISE NOTICE 'old_column_list=%', old_column_list; 
ctas_stmt = format('CREATE TABLE %s AS SELECT %s from %s', p_new_table, old_column_list, p_old_table); 
RAISE NOTICE 'ctas_stmt=%', ctas_stmt; 
EXECUTE ctas_stmt;
END;
$BODY$;
--
create table t(x int, y text, z timestamp, z1 text);
insert into t values (1, 'OK', current_timestamp, null);
select * from t;
--
call test('t',ARRAY['x','y','z'], 'tmp');
--
\d tmp;
select * from tmp;

I have following execution:

CREATE OR REPLACE PROCEDURE public.test(IN p_old_table text, IN p_old_column_names text[], IN p_new_table text)
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE  
   old_column_list text;
   ctas_stmt text;
BEGIN
old_column_list = array_to_string(p_old_column_names,',');
RAISE NOTICE 'old_column_list=%', old_column_list; 
ctas_stmt = format('CREATE TABLE %s AS SELECT %s from %s', p_new_table, old_column_list, p_old_table); 
RAISE NOTICE 'ctas_stmt=%', ctas_stmt; 
EXECUTE ctas_stmt;
END;
$BODY$;
CREATE PROCEDURE

create table t(x int, y text, z timestamp, z1 text);
CREATE TABLE

insert into t values (1, 'OK', current_timestamp, null);
INSERT 0 1

select * from t;
 x | y  |             z              | z1 
---+----+----------------------------+----
 1 | OK | 2020-04-14 11:37:28.641328 | 
(1 row)

call test('t',ARRAY['x','y','z'], 'tmp');
psql:tvar.sql:24: NOTICE:  old_column_list=x,y,z
psql:tvar.sql:24: NOTICE:  ctas_stmt=CREATE TABLE tmp AS SELECT x,y,z from t
CALL

                          Table "public.tmp"
 Column |            Type             | Collation | Nullable | Default 
--------+-----------------------------+-----------+----------+---------
 x      | integer                     |           |          | 
 y      | text                        |           |          | 
 z      | timestamp without time zone |           |          | 

select * from tmp;
 x | y  |             z              
---+----+----------------------------
 1 | OK | 2020-04-14 11:37:28.641328
(1 row)

Thanks for your question!! But, with this script, my problem is not solved, no? My objective is to create a table with one unique column. The value of that column is all the values of the columns that I pass as a parameter in the function, separated by a comma. I've changed my question a bit, maybe it wasn't clear. Sorry for that.

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