class DuckDB::Expression

DuckDB::Expression represents a DuckDB expression object.

Instances are returned by DuckDB::ScalarFunction::BindInfo#get_argument during the bind phase of a scalar function.

Public Instance Methods

Source

# File lib/duckdb/expression.rb, line 18
def fold(client_context)
  raise DuckDB::Error, 'expression is not foldable' unless foldable?

  _fold(client_context)
end

Evaluates the expression at planning time and returns a DuckDB::Value holding the constant result. Raises DuckDB::Error if the expression is not foldable.

sf.set_bind do |bind_info|
  expr           = bind_info.get_argument(0)
  client_context = bind_info.client_context
  value          = expr.fold(client_context)   # => DuckDB::Value
end

foldable? → true or false

Source

static VALUE rbduckdb_expression_foldable_p(VALUE self) {
    rubyDuckDBExpression *ctx;
    TypedData_Get_Struct(self, rubyDuckDBExpression, &expression_data_type, ctx);
    return duckdb_expression_is_foldable(ctx->expression) ? Qtrue : Qfalse;
}

Returns true if the expression can be folded to a constant at query planning time (e.g. literals, constant arithmetic), false otherwise (e.g. column references, non-deterministic functions).