Class: DuckDB::TableDescription

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

Overview

DuckDB::TableDescription provides metadata about a table in DuckDB.

Use it to retrieve column descriptions — including name, logical type, and whether a column has a default value — for any accessible table.

Requires DuckDB >= 1.5.0.

require 'duckdb'
db = DuckDB::Database.open
con = db.connect
con.query('CREATE TABLE users (id INTEGER, name VARCHAR DEFAULT \'anonymous\')')

td = DuckDB::TableDescription.new(con, 'users')
td.column_descriptions.each do |cd|
  puts "#{cd.name}: #{cd.logical_type.type}, default=#{cd.has_default?}"
end
# id: integer, default=false
# name: varchar, default=true

Instance Method Summary collapse

Constructor Details

#initialize(con, table, schema: nil, catalog: nil) ⇒ TableDescription

Creates a new TableDescription for the given table.

con must be a DuckDB::Connection. table is the table name (String). Optionally pass schema: and/or catalog: to qualify the table.

Raises DuckDB::Error if the connection is invalid, the table name is nil, or the table (or schema/catalog) does not exist.

require 'duckdb'
db = DuckDB::Database.open
con = db.connect
con.query('CREATE TABLE t (i INTEGER)')

DuckDB::TableDescription.new(con, 't')
DuckDB::TableDescription.new(con, 't', schema: 'main')

Raises:



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# File 'lib/duckdb/table_description.rb', line 39

def initialize(con, table, schema: nil, catalog: nil)
  raise DuckDB::Error, '1st argument must be DuckDB::Connection object.' unless con.is_a?(DuckDB::Connection)
  raise DuckDB::Error, '2nd argument must be table name.' if table.nil?

  raise DuckDB::Error, error_message unless _initialize(con, catalog, schema, table)
end

Instance Method Details

#column_descriptions ⇒ Object

Returns an array of DuckDB::ColumnDescription objects, one per column.

Each element describes a single column’s name, logical type, and whether it has a default value defined.

require 'duckdb'
db = DuckDB::Database.open
con = db.connect
con.query("CREATE TABLE t (i INTEGER, j INTEGER DEFAULT 5)")

td = DuckDB::TableDescription.new(con, 't')
td.column_descriptions
#=> [#<data DuckDB::ColumnDescription name="i" ...>, ...]



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# File 'lib/duckdb/table_description.rb', line 59

def column_descriptions
  Array.new(_column_count) do |i|
    ColumnDescription.new(
      name: _column_name(i),
      logical_type: _column_logical_type(i),
      has_default: _column_has_default?(i)
    )
  end
end

#error_message ⇒ Object 



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# File 'ext/duckdb/table_description.c', line 49

static VALUE rbduckdb_table_description_error_message(VALUE self) {
    rubyDuckDBTableDescription *ctx = get_struct_table_description(self);
    const char *p = duckdb_table_description_error(ctx->table_description);
    return p ? rb_str_new2(p) : Qnil;
}