ruby-duckdb¶ ↑

Description¶ ↑

This gem duckdb is Ruby client for the DuckDB database engine.

Requirement¶ ↑

You must have DuckDB engine installed in order to use this gem.

Pre-requisite setup (Linux):¶ ↑

1. Head over to the DuckDB webpage.

2. Download the latest C++ package release for DuckDB.

3. Move the files to their respective location:

   • Extract the duckdb.h and duckdb.hpp file to /usr/local/include.

   • Extract the libduckdb.so file to /usr/local/lib.

   unzip libduckdb-linux-amd64.zip -d libduckdb
   sudo mv libduckdb/duckdb.* /usr/local/include/
   sudo mv libduckdb/libduckdb.so /usr/local/lib

4. To create the necessary link, run ldconfig as root:

   sudo ldconfig /usr/local/lib # adding a --verbose flag is optional - but this will let you know if the libduckdb.so library has been linked

Pre-requisite setup (macOS):¶ ↑

Using brew install is recommended.

brew install duckdb

Pre-requisite setup (Windows):¶ ↑

Using Ruby + Devkit is recommended.

1. Download libduckdb-windows-amd64.zip from DuckDB and extract it.

2. Copy duckdb.dll into C:\Windows\System32

How to install¶ ↑

gem install duckdb

After you’ve run the above pre-requisite setup, this should work fine.

If it doesn’t, you may have to specify the location of the C header and library files:

gem install duckdb -- --with-duckdb-include=/duckdb_header_directory --with-duckdb-lib=/duckdb_library_directory

Usage¶ ↑

The followings are some examples, for more detailed information, please refer to the documentation.

require 'duckdb'

db = DuckDB::Database.open # database in memory
con = db.connect

con.query('CREATE TABLE users (id INTEGER, name VARCHAR(30))')

con.query("INSERT into users VALUES(1, 'Alice')")
con.query("INSERT into users VALUES(2, 'Bob')")
con.query("INSERT into users VALUES(3, 'Cathy')")

result = con.query('SELECT * from users')
result.each do |row|
  puts row
end

Or, you can use block.

require 'duckdb'

DuckDB::Database.open do |db|
  db.connect do |con|
    con.query('CREATE TABLE users (id INTEGER, name VARCHAR(30))')

    con.query("INSERT into users VALUES(1, 'Alice')")
    con.query("INSERT into users VALUES(2, 'Bob')")
    con.query("INSERT into users VALUES(3, 'Cathy')")

    result = con.query('SELECT * from users')
    result.each do |row|
      puts row
    end
  end
end

Using bind variables¶ ↑

You can use bind variables.

con.query('SELECT * FROM users WHERE name = ? AND email = ?', 'Alice', 'alice@example.com')
# or
con.query('SELECT * FROM users WHERE name = $name AND email = $email', name: 'Alice', email: 'alice@example.com')

Using prepared statement¶ ↑

You can use prepared statement. Prepared statement object is created by Connection#prepare method or DuckDB::PreparedStatement.new.

stmt = con.prepare('SELECT * FROM users WHERE name = $name AND email = $email')
# or
# stmt = con.prepared_statement('SELECT * FROM users WHERE name = $name AND email = $email')
# or
# stmt = DuckDB::PreparedStatement.new(con, 'SELECT * FROM users WHERE name = $name AND email = $email')
stmt.bind(name: 'Alice', email: 'alice@example.com')
result = stmt.execute
stmt.destroy

You must call PreparedStatement#destroy method after using prepared statement. Otherwise, automatically destroyed when the PreparedStatement object is garbage collected.

Instead of calling PreparedStatement#destroy, you can use block.

result = con.prepare('SELECT * FROM users WHERE name = $name AND email = $email') do |stmt|
           stmt.bind(name: 'Alice', email: 'alice@example.com')
           stmt.execute
         end

Using async query¶ ↑

You can use async query.

pending_result = con.async_query_stream('SLOW QUERY')
pending_result.execute_task while pending_result.state == :not_ready

result = pending_result.execute_pending
result.each.first

Here is the benchmark.

Using BLOB column¶ ↑

Use DuckDB::Blob.new or my_string.force_encoding(Encoding::BINARY).

require 'duckdb'

DuckDB::Database.open do |db|
  db.connect do |con|
    con.query('CREATE TABLE blob_table (binary_data BLOB)')
    stmt = DuckDB::PreparedStatement.new(con, 'INSERT INTO blob_table VALUES ($1)')

    stmt.bind(1, DuckDB::Blob.new("\0\1\2\3\4\5"))
    # or
    # stmt.bind(1, "\0\1\2\3\4\5".force_encoding(Encoding::BINARY))
    stmt.execute

    result = con.query('SELECT binary_data FROM blob_table')
    puts result.first.first
  end
end

Appender¶ ↑

Appender class provides Ruby interface of DuckDB Appender

require 'duckdb'
require 'benchmark'

def insert
  DuckDB::Database.open do |db|
    db.connect do |con|
      con.query('CREATE TABLE users (id INTEGER, name VARCHAR(30))')

      10000.times do
        con.query("INSERT into users VALUES(1, 'Alice')")
      end
    end
  end
end

def prepare
  DuckDB::Database.open do |db|
    db.connect do |con|
      con.query('CREATE TABLE users (id INTEGER, name VARCHAR(30))')
      stmt = con.prepared_statement('INSERT INTO users VALUES($1, $2)')

      10000.times do
        stmt.bind(1, 1)
        stmt.bind(2, 'Alice')
        stmt.execute
      end
    end
  end
end

def append
  DuckDB::Database.open do |db|
    db.connect do |con|
      con.query('CREATE TABLE users (id INTEGER, name VARCHAR(30))')
      appender = con.appender('users')

      10000.times do
        appender.append(1)
        appender.append('Alice')
        appender.end_row
      end

      appender.flush
    end
  end
end

Benchmark.bm(8) do |x|
  x.report('insert') { insert }
  x.report('prepare') { prepare }
  x.report('append') { append }
end

# =>
#                user     system      total        real
# insert     0.637439   0.000000   0.637439 (  0.637486 )
# prepare    0.230457   0.000000   0.230457 (  0.230460 )
# append     0.012666   0.000000   0.012666 (  0.012670 )

Configuration¶ ↑

Config class provides Ruby interface of DuckDB configuration.

require 'duckdb'

config = DuckDB::Config.new
config['default_order'] = 'DESC'

db = DuckDB::Database.open(nil, config)

con = db.connect
con.query('CREATE TABLE numbers (number INTEGER)')
con.query('INSERT INTO numbers VALUES (2), (1), (4), (3)')

# number is ordered by descending
res = con.query('SELECT number FROM numbers ORDER BY number')
res.first.first # => 4