Approaches to execute PostgreSQL's concat() instead of || in JOOQ? - postgresql

Question

The ||-operator and the concat(...)-function in PostgreSQL behave differently.
select 'ABC'||NULL||'def';
-- Result: NULL
select concat('ABC', NULL, 'def');
-- Result: 'ABCdef'
concat(...) ignores NULL values, but a NULL whithin a || expression makes the whole result become NULL.
In JOOQ, the DSL.concat() in the PostgreSQL dialect renders expressions using the ||-operator:
Java: dsl.select(
DSL.concat(
DSL.inline("ABC"),
DSL.inline(null, SQLDataType.VARCHAR),
DSL.inline("def"))
).execute();
SQL: select ('ABC' || null || 'def')
Result: NULL
I am looking for (elegant?) ways to invoke the concat(...)-function instead of the ||-operator via JOOQ in PostgreSQL:
Java: dsl.select(???).execute();
SQL: select concat('ABC', null, 'def')
Result: 'ABCdef'

Answer 1

I found two ways to achieve the posed objective.
Approach #1:
dsl.select(
field(
"concat({0})",
SQLDataType.VARCHAR,
list(
inline("ABC"),
inline(null, SQLDataType.VARCHAR),
inline("def")
)
)
).execute();
This has to the intended behavior, but necessitates the in my eyes ugly "concat({0})". A more elegant approach from my point of view is:
Approach #2:
dsl.select(
function(
"concat",
SQLDataType.VARCHAR,
inline("ABC"),
inline(null, SQLDataType.VARCHAR),
inline("def")
)
).execute();
This solution does not involve inline SQL with placeholders as approach #1. Why JOOQ generates || instead of concat(...) in the first place is still to be expounded, though.