Unknown function btrim

[Anton Shvetsov]

Hi guys.

I tried to use function trim in "where" block in postgres and got the error message: "Unknown function btrim QUERY:SELECT field FROM "default".test_table WHERE ((btrim(field) <> ''))"

How to reproduce:

1. Create table in ClickHouse

create table test_table (field String) engine = MergeTree() ORDER BY (field);

2. Add value to table

insert into test_table values ('213');

3. Create fdw table in postgres

create foreign table test_table ("field" text) server clickhouse_svr;

4. Select data and use function trim in where

select * from test_table where trim(field) <> '';

I checked on versions:

• PostgreSQL 12.3 (Debian 12.3-1.pgdg110+1+b1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 9.3.0-14) 9.3.0, 64-bit
• ClickHouse Verion 20.5.4.40

[Anton Shvetsov]

I found workaround. But it's very strange

You can use functions ltrim, rtrim together. It works.

select * from test_table where ltrim(rtrim(field)) <> '';

[Ildus Kurbangaliev]

It's not strange, clickhouse already has ltrim and rtrim functions, but not btrim. I haved added translation to trimBoth.