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dgw generates Golang struct, and simple Table/Row Data Gateway functions from PostgreSQL table metadata
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README.md

dgw

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Description

dgw generates Golang struct, and simple Table/Row Data Gateway functions from PostgreSQL table metadata. Heavily inspired by xo.

Why created

Personally, I prefer Table/Row Data Gateway over ORM/Query Builder approach when using Go with RDBMS. However, it is very time consuming, tedious, and error-prone to write a lot of columns, query place holders, and struct fields that all have to be exactly in order even for a simple select/insert statement. dgw generate Go struct, and simple functions to get/create row from PostgreSQL table definitions to avoid manually writing simple but tedious SQL.

  • dgw can properly detect autogenerated column (e.g. serial, bigserial), and composit primary key to create appropriate SQL.
  • dgw has ability to easily customize PostgreSQL column type <-> Go type mapping using toml config file.

Installation

go get -u github.com/achiku/dgw

How to use

usage: dgw [<flags>] <conn>

Flags:
      --help                 Show context-sensitive help (also try --help-long and --help-man).
  -s, --schema="public"      PostgreSQL schema name
  -p, --package="main"       package name
  -t, --typemap=TYPEMAP      column type and go type map file path
  -x, --exclude=EXCLUDE ...  table names to exclude
      --template=TEMPLATE    custom template path
  -o, --output=OUTPUT        output file path
      --no-interface         output without Queryer interface

Args:
  <conn>  PostgreSQL connection string in URL format
dgw postgres://dbuser@localhost/dbname?sslmode=disable 

Example

CREATE TABLE t1 (
  id bigserial primary key
  , i integer not null unique
  , str text not null
  , num_float numeric not null
  , nullable_str text
  , t_with_tz timestamp without time zone not null
  , t_without_tz timestamp with time zone not null
  , nullable_tz timestamp with time zone
  , json_data json not null
  , xml_data xml not null
);

CREATE TABLE t2 (
  id bigserial not null
  , i integer not null
  , str text not null
  , t_with_tz timestamp without time zone not null
  , t_without_tz timestamp with time zone not null
  , PRIMARY KEY(id, i)
);

CREATE TABLE t3 (
  id integer not null
  , i integer not null
  , PRIMARY KEY(id, i)
);

Generate Go code by the following command.

$ dgw postgres://dgw_test@localhost/dgw_test?sslmode=disable --typemap=./typemap.toml --schema=public --package=dgwexample --output=example.go
// T1 represents public.t1
type T1 struct {
	ID          int64          // id
	I           int            // i
	Str         string         // str
	NumFloat    float64        // num_float
	NullableStr sql.NullString // nullable_str
	TWithTz     time.Time      // t_with_tz
	TWithoutTz  time.Time      // t_without_tz
	NullableTz  *time.Time     // nullable_tz
	JSONData    []byte         // json_data
	XMLData     []byte         // xml_data
}

// Create inserts the T1 to the database.
func (r *T1) Create(db Queryer) error {
	err := db.QueryRow(
		`INSERT INTO t1 (i, str, num_float, nullable_str, t_with_tz, t_without_tz, nullable_tz, json_data, xml_data) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9) RETURNING id`,
		&r.I, &r.Str, &r.NumFloat, &r.NullableStr, &r.TWithTz, &r.TWithoutTz, &r.NullableTz, &r.JSONData, &r.XMLData).Scan(&r.ID)
	if err != nil {
		return errors.Wrap(err, "failed to insert t1")
	}
	return nil
}

// GetT1ByPk select the T1 from the database.
func GetT1ByPk(db Queryer, pk0 int64) (*T1, error) {
	var r T1
	err := db.QueryRow(
		`SELECT id, i, str, num_float, nullable_str, t_with_tz, t_without_tz, nullable_tz, json_data, xml_data FROM t1 WHERE id = $1`,
		pk0).Scan(&r.ID, &r.I, &r.Str, &r.NumFloat, &r.NullableStr, &r.TWithTz, &r.TWithoutTz, &r.NullableTz, &r.JSONData, &r.XMLData)
	if err != nil {
		return nil, errors.Wrap(err, "failed to select t1")
	}
	return &r, nil
}

// T2 represents public.t2
type T2 struct {
	ID         int64     // id
	I          int       // i
	Str        string    // str
	TWithTz    time.Time // t_with_tz
	TWithoutTz time.Time // t_without_tz
}

// Create inserts the T2 to the database.
func (r *T2) Create(db Queryer) error {
	err := db.QueryRow(
		`INSERT INTO t2 (str, t_with_tz, t_without_tz) VALUES ($1, $2, $3) RETURNING id, i`,
		&r.Str, &r.TWithTz, &r.TWithoutTz).Scan(&r.ID, &r.I)
	if err != nil {
		return errors.Wrap(err, "failed to insert t2")
	}
	return nil
}

// GetT2ByPk select the T2 from the database.
func GetT2ByPk(db Queryer, pk0 int64, pk1 int) (*T2, error) {
	var r T2
	err := db.QueryRow(
		`SELECT id, i, str, t_with_tz, t_without_tz FROM t2 WHERE id = $1 AND i = $2`,
		pk0, pk1).Scan(&r.ID, &r.I, &r.Str, &r.TWithTz, &r.TWithoutTz)
	if err != nil {
		return nil, errors.Wrap(err, "failed to select t2")
	}
	return &r, nil
}

// T3 represents public.t3
type T3 struct {
	ID int // id
	I  int // i
}

// Create inserts the T3 to the database.
func (r *T3) Create(db Queryer) error {
	_, err := db.Exec(
		`INSERT INTO t3 (id, i) VALUES ($1, $2)`,
		&r.ID, &r.I)
	if err != nil {
		return errors.Wrap(err, "failed to insert t3")
	}
	return nil
}

// GetT3ByPk select the T3 from the database.
func GetT3ByPk(db Queryer, pk0 int, pk1 int) (*T3, error) {
	var r T3
	err := db.QueryRow(
		`SELECT id, i FROM t3 WHERE id = $1 AND i = $2`,
		pk0, pk1).Scan(&r.ID, &r.I)
	if err != nil {
		return nil, errors.Wrap(err, "failed to select t3")
	}
	return &r, nil
}

Test

$ psql -d template1
> CREATE USER dgw_test;
> CREATE DATABASE  dgw_test OWNER dgw_test;
> \q
$ go get -u github.com/golang/dep/cmd/dep
$ dep ensure
$ go test
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