Go SQL driver for DuckDB

The DuckDB driver conforms to the built-in database/sql interface.

Installation

go get github.com/marcboeker/go-duckdb

Windows

On windows, the correct version of gcc and the neccesary runtime libraries needs to be installed. One method to do this is using msys64. To begin, install msys64 using their installer. Once this is done, open a msys64 shell and run

pacman -S mingw-w64-ucrt-x86_64-gcc

select yes when neccesary, its ok if the shell closes. Then add gcc to the path using whatever method you prefer. In powershell this is $env:PATH = "C:\msys64\ucrt64\bin:$env:PATH". Once this is done, you can compile this package on windows.

Usage

go-duckdb hooks into the database/sql interface provided by the Go stdlib. To open a connection, simply specify the driver type as duckdb.

db, err := sql.Open("duckdb", "")
check(err)
defer db.Close()

This creates an in-memory instance of DuckDB. To open a persistent database, you need to specify a filepath to the database file. If the file does not exist, then DuckDB creates it.

db, err := sql.Open("duckdb", "/path/to/foo.db")
check(err)
defer db.Close()

If you want to set specific config options for DuckDB, you can add them as query style parameters in the form of name=value pairs to the DSN.

db, err := sql.Open("duckdb", "/path/to/foo.db?access_mode=read_only&threads=4")
check(err)
defer db.Close()

Alternatively, you can use sql.OpenDB. That way, you can perform initialization steps in a callback function before opening the database. Here's an example that configures some database parameters when opening a database with sql.OpenDB(connector).

connector, err := duckdb.NewConnector("/path/to/foo.db?access_mode=read_only&threads=4", func(execer driver.ExecerContext) error {
    bootQueries := []string{
        "SET schema=main",
        "SET search_path=main",
    }

    for _, query := range bootQueries {
        _, err = execer.ExecContext(context.Background(), query, nil)
        if err != nil {
			return err
        }
    }
    return nil
})
check(err)

db := sql.OpenDB(connector)
defer db.Close()

Please refer to the database/sql documentation for further usage instructions.

Notes and FAQs

undefined: conn

When building this package, some people run into an undefined: conn error. This is due to the go compiler determining that CGO is not available. This can happen due to a few issues.

The first noted in the comment here is that the buildtools are not installed. To fix this for ubuntu, you can install them using:

sudo apt-get update && sudo apt-get install build-essential

Another issue is when you are cross-compiling, since the go compiler automatically disables CGO when cross-compiling. To enable cgo when cross-compiling use CC={C cross compiler} CGO_ENABLED=1 {command} to force-enable CGO and set the right cross-compiler.

TIMESTAMP vs. TIMESTAMP_TZ

In the C API, DuckDB stores both TIMESTAMP and TIMESTAMP_TZ as duckdb_timestamp, which holds the number of microseconds elapsed since January 1, 1970 UTC (i.e., an instant without offset information). When passing a time.Time to go-duckdb, go-duckdb transforms it to an instant with UnixMicro(), even when using TIMESTAMP_TZ. Later, scanning either type of value returns an instant, as SQL types do not model time zone information for individual values.

Memory Allocation

DuckDB lives in-process. Therefore, all its memory lives in the driver. All allocations live in the host process, which is the Go application. Especially for long-running applications, it is crucial to call the corresponding Close-functions as specified in database/sql. The following is a list of examples.

db, err := sql.Open("duckdb", "")
defer db.Close()

conn, err := db.Conn(context.Background())
defer conn.Close()

rows, err := conn.QueryContext(context.Background(), "SELECT 42")
// Alternatively, rows.Next() has to return false.
rows.Close()

appender, err := NewAppenderFromConn(conn, "", "test")
defer appender.Close()

// If not passed to sql.OpenDB.
connector, err := NewConnector("", nil)
defer connector.Close()

DuckDB Appender API

If you want to use the DuckDB Appender API, you can obtain a new Appender by passing a DuckDB connection to NewAppenderFromConn(). See examples/appender.go for a complete example.

connector, err := duckdb.NewConnector("test.db", nil)
check(err)
defer connector.Close()

conn, err := connector.Connect(context.Background())
check(err)
defer conn.Close()

// Obtain an appender from the connection.
// NOTE: The table 'test_tbl' must exist in test.db.
appender, err := NewAppenderFromConn(conn, "", "test_tbl")
check(err)
defer appender.Close()

err = appender.AppendRow(...)
check(err)

DuckDB Profiling API

This section describes using the DuckDB Profiling API. DuckDB's profiling information is connection-local. The following example walks you through the necessary steps to obtain the ProfilingInfo type, which contains all available metrics. Please refer to the DuckDB documentation on configuring and collecting specific metrics.

• First, you need to obtain a connection.
• Then, you enable profiling for the connection.
• Now, for each subsequent query on this connection, DuckDB will collect profiling information.
  • Optionally, you can turn off profiling at any point.
• Next, you execute the query for which you want to obtain profiling information.
• Finally, directly after executing the query, retrieve any available profiling information.

For readability, we omit error handling in this example.

db, err := sql.Open("duckdb", "")
con, err := db.Conn(context.Background())

_, err = con.ExecContext(context.Background(), `PRAGMA enable_profiling = 'no_output'`)
_, err = con.ExecContext(context.Background(), `PRAGMA profiling_mode = 'detailed'`)

res, err := con.QueryContext(context.Background(), `SELECT 42`)
info, err := GetProfilingInfo(con)
err = res.Close()

_, err = con.ExecContext(context.Background(), `PRAGMA disable_profiling`)
err = con.Close()
err = db.Close()

DuckDB Apache Arrow Interface

If you want to use the DuckDB Arrow Interface, you can obtain a new Arrow by passing a DuckDB connection to NewArrowFromConn().

connector, err := duckdb.NewConnector("", nil)
check(err)
defer connector.Close()

conn, err := connector.Connect(context.Background())
check(err)
defer conn.Close()

// Obtain the Arrow from the connection.
arrow, err := duckdb.NewArrowFromConn(conn)
check(err)

rdr, err := arrow.QueryContext(context.Background(), "SELECT * FROM generate_series(1, 10)")
check(err)
defer rdr.Release()

for rdr.Next() {
  // Process each record.
}

The Arrow interface is a heavy dependency. If you do not need it, you can disable it by passing -tags=no_duckdb_arrow to go build. This will be made opt-in in V2.

go build -tags="no_duckdb_arrow"

Vendoring

If you want to vendor a module containing go-duckdb, please use modvendor to include the missing header files and libraries. See issue #174 for more details.

1. go install github.com/goware/modvendor@latest
2. go mod vendor
3. modvendor -copy="**/*.a **/*.h" -v

Now you can build your module as usual.

Linking DuckDB

By default, go-duckdb statically links DuckDB into your binary. Statically linking DuckDB increases your binary size.

go-duckdb bundles pre-compiled static libraries for some OS and architecture combinations.

• MacOS: amd64, arm64.
• Linux: amd64, arm64.
• FreeBSD: amd64.
• Windows: amd64.

Alternatively, you can dynamically link DuckDB by passing -tags=duckdb_use_lib to go build. You must have a copy of libduckdb available on your system (.so on Linux or .dylib on macOS), which you can download from the DuckDB releases page. For example:

# On Linux.
CGO_ENABLED=1 CGO_LDFLAGS="-L/path/to/libs" go build -tags=duckdb_use_lib main.go
LD_LIBRARY_PATH=/path/to/libs ./main

# On macOS.
CGO_ENABLED=1 CGO_LDFLAGS="-L/path/to/libs" go build -tags=duckdb_use_lib main.go
DYLD_LIBRARY_PATH=/path/to/libs ./main

DuckDB Extensions

go-duckdb statically builds the JSON extension for its pre-compiled libraries. Additionally, automatic extension loading is enabled. The extensions available differ between the pre-compiled libraries. Thus, if you fail to install and load an extension, you might have to link a custom DuckDB.

Specifically, for MingW (Windows), there are no distributed extensions (yet). You can statically include them by extending the BUILD_EXTENSIONS="json" variable in the Makefile.