Class: DuckDB::Expression

Inherits:
Object
  • Object
show all
Defined in:
lib/duckdb/expression.rb,
ext/duckdb/expression.c

Overview

DuckDB::Expression represents a DuckDB expression object.

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

Instance Method Summary collapse

Instance Method Details

#fold(client_context) ⇒ Object

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

Raises:



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# File 'lib/duckdb/expression.rb', line 18

def fold(client_context)
  raise DuckDB::Error, 'expression is not foldable' unless foldable?

  _fold(client_context)
end

#foldable? ⇒ Boolean

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).

Returns:

  • (Boolean) 


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# File 'ext/duckdb/expression.c', line 54

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;
}