Avoid "String is too long" Warning with LISTAGG in Snowflake

Question

I have been using the LISTAGG function in Snowflake to concatenate strings and I triggered the following warning:

100078 (22000): String '(LISTAGG result)' is too long and would be truncated

I understand that this warning is triggered when the aggregated string exceeds a certain length. I want to know the best practices to prevent or handle this warning, given that truncation is fine and not relevant for the quality of column. Should I truncate in advance the result? If so, how?

SELECT
        userid,
        NULLIF(LISTAGG(DISTINCT city, ', '), '') AS cities,
        NULLIF(LISTAGG(DISTINCT region, ', '), '') AS regions,
        ...
FROM {{ ref('myschema.table_T') }}
GROUP BY userid

Answer 1

Since the aggregates string reach the limit, you can't use the LISTAGG function. You could create a user-defined aggregate function instead :

create or replace function full_array_agg(g string, s string)
returns table (G string, S array)
language javascript
as $$
{
    processRow: function f(row, rowWriter, context){
        if( this.arr.indexOf(row.S) === -1 ) {
          this.arr.push(row.S)
        }
        this.group = row.G
        this.counter++;
    }
    , initialize: function(argumentInfo, context) {
        this.counter = 0;
        this.arr = [];
    }, finalize: function(rowWriter, context){
        rowWriter.writeRow({G:this.group, S: this.arr})
    }
}
$$;

You can use it like this :

select cities.g as userid, cities.s as cities
from mytable
    , table(full_array_agg(
        userid::string, 
        city) over(partition by userid)) cities;

Inspired from this answer :

• String '(LISTAGG result)' is too long and would be truncated - How to fix this?