Go SQL Driver For DuckDB

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

Current DuckDB version: v1.2.2.

The first go-duckdb tag with that version is v2.2.0.

Previous DuckDB versions:

DuckDB	go-duckdb
`v1.2.1`	`v2.1.0`
`v1.2.0`	`v2.0.3`
`v1.1.3`	`v1.8.5`

Breaking Changes

! Starting with v2.0.0, go-duckdb supports DuckDB v1.2.0 and upward.
! Moving to v2 includes the following breaking changes:

Dropping pre-built FreeBSD support

Starting with v2, go-duckdb drops pre-built FreeBSD support. This change is because DuckDB does not publish any bundled FreeBSD libraries. Thus, you must build your static library for FreeBSD using the steps below.

The Arrow dependency is now opt-in

The DuckDB Arrow Interface is a heavy dependency. Starting with v2, the DuckDB Arrow Interface is opt-in instead of opt-out. If you want to use it, you can enable it by passing -tags=duckdb_arrow to go build.

JSON type scanning changes

The pre-built libraries ship DuckDB's JSON extension containing the JSON type. Pre-v2, it was possible to scan a JSON type into []byte via Rows.Scan. However, scanning into any (driver.Value) would cause the JSON string to contain escape characters and other unexpected behavior.

It is now possible to scan into any, or directly into go-duckdb's Composite type, as shown in the JSON example. Scanning directly into string or []byte is no longer possible. A workaround is casting to ::VARCHAR or ::BLOB in DuckDB if you do not need to scan the result into a JSON interface.

Installation

go get github.com/marcboeker/go-duckdb/v2

Windows

You must have the correct version of gcc and the necessary runtime libraries installed on Windows. One method to do this is using msys64. To begin, install msys64 using their installer. Once you installed msys64, open a msys64 shell and run:

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

Select "yes" when necessary; it is okay 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". After, you can compile this package in Windows.

Vendoring

You can use go mod vendor to make a copy of the third-party packages in this package, including the pre-built DuckDB libraries in duckdb-go-bindings.

Usage

Note: For readability, we omit error handling in most examples.

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

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

The above lines create an in-memory instance of DuckDB. To open a persistent database, specify a file path to the database file. If the file does not exist, then DuckDB creates it.

db, err := sql.Open("duckdb", "/path/to/foo.db")
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")
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 parameters when opening a database with sql.OpenDB(connector).

c, 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
})
defer c.Close()
db := sql.OpenDB(c)
defer db.Close()

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

Linking DuckDB

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

go-duckdb bundles the following pre-compiled static libraries.

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

Linking a Static Library

If none of the pre-built libraries satisfy your needs, you can build a custom static library.

Clone and build the DuckDB source code.
- Use their bundle-library Makefile target (e.g., make bundle-library).
- Common build flags are: DUCKDB_PLATFORM=any BUILD_EXTENSIONS="icu;json;parquet;autocomplete".
- See DuckDB's development instructions for more details.
Link against the resulting static library, which you can find in: duckdb/build/release/libduckdb_bundle.a.

For Darwin ARM64, you can then build your module like so:

CGO_ENABLED=1 CPPFLAGS="-DDUCKDB_STATIC_BUILD" CGO_LDFLAGS="-lduckdb_bundle -lc++ -L/path/to/libs" go build -tags=duckdb_use_static_lib

You can also find these steps in the Makefile and the tests.yaml. The DuckDB team also publishes some pre-built bundled libraries as part of their releases.

Note on FreeBSD

Starting with v2, go-duckdb drops pre-built FreeBSD support. This change is because DuckDB does not publish any bundled FreeBSD libraries. Thus, you must build your static library for FreeBSD using the steps above.

Linking a Dynamic Library

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="-lduckdb -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="-lduckdb -L/path/to/libs" go build -tags=duckdb_use_lib main.go
DYLD_LIBRARY_PATH=/path/to/libs ./main

You can also find these steps in the Makefile and the tests.yaml.

Notes and FAQs

undefined: conn

Some people encounter an undefined: conn error when building this package. This error is due to the Go compiler determining that CGO is unavailable. This error can happen due to a few issues.

The first cause, as noted in the comment here, might be 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 cause can be cross-compilation 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()

c, err := NewConnector("", nil)
// Optional, if passed to sql.OpenDB.
defer c.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.

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

conn, err := c.Connect(context.Background())
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")
defer appender.Close()

err = appender.AppendRow(...)

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.

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

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

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

res, err := conn.QueryContext(context.Background(), `SELECT 42`)
defer res.Close()

info, err := GetProfilingInfo(conn)

_, err = conn.ExecContext(context.Background(), `PRAGMA disable_profiling`)

DuckDB Apache Arrow Interface

The DuckDB Arrow Interface is a heavy dependency. Starting with v2, the DuckDB Arrow Interface is opt-in instead of opt-out. If you want to use it, you can enable it by passing -tags=duckdb_arrow to go build.

go build -tags="duckdb_arrow"

You can obtain a new Arrow by passing a DuckDB connection to NewArrowFromConn().

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

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

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

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

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

DuckDB Extensions

go-duckdb relies on the duckdb-go-bindings module. Any pre-built library in duckdb-go-bindings statically links the default extensions: ICU, JSON, Parquet, and Autocomplete. Additionally, automatic extension loading is enabled.

License

rilldata/go-duckdb

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