Compare · 015

Nested structs with sgl.embed: SQLite and PostgreSQL

Every file of the SQLite and PostgreSQL versions side by side, with the lines that differ marked. 2 parameter or column types differ in Go.

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Configuration

sgl.yamldiffers
SQLite
PostgreSQL
1version: 1
1version: 1
2
2
3databases:
3databases:
4 - name: fleet
4 - name: fleet
5 dialect: sqlite
5 dialect: postgres
6 migrations: db/migrations
6 migrations: db/migrations
7 queries: db/queries
7 queries: db/queries
8 go:
8 go:
9 package: store
9 package: store
10 out: internal/store
10 out: internal/store
11 driver: database/sql

Migrations

db/migrations/0001_fleet.up.sqldiffers
SQLite
PostgreSQL
1CREATE TABLE harbours (
1CREATE TABLE harbours (
2 id INTEGER PRIMARY KEY,
2 id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
3 name TEXT NOT NULL,
3 name TEXT NOT NULL,
4 county TEXT NOT NULL
4 county TEXT NOT NULL
5);
5);
6
6
7CREATE TABLE skippers (
7CREATE TABLE skippers (
8 id INTEGER PRIMARY KEY,
8 id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
9 name TEXT NOT NULL,
9 name TEXT NOT NULL,
10 licence TEXT NOT NULL
10 licence TEXT NOT NULL
11);
11);
12
12
13CREATE TABLE boats (
13CREATE TABLE boats (
14 id INTEGER PRIMARY KEY,
14 id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
15 name TEXT NOT NULL,
15 name TEXT NOT NULL,
16 harbour_id INTEGER NOT NULL REFERENCES harbours (id),
16 harbour_id BIGINT NOT NULL REFERENCES harbours (id),
17 skipper_id INTEGER REFERENCES skippers (id)
17 skipper_id BIGINT REFERENCES skippers (id)
18);
18);
db/migrations/0001_fleet.down.sqlidentical
SQLite
PostgreSQL
1DROP TABLE boats;
1DROP TABLE boats;
2DROP TABLE skippers;
2DROP TABLE skippers;
3DROP TABLE harbours;
3DROP TABLE harbours;

Queries

AddHarbourdiffers
SQLite · db/queries/boats.sql
PostgreSQL · db/queries/boats.sql
1-- sgl.query(AddHarbour, exec)
1-- sgl.query(AddHarbour, exec)
2INSERT INTO harbours (name, county) VALUES (?, ?);
2INSERT INTO harbours (name, county) VALUES ($1, $2);
AddSkipperdiffers
SQLite · db/queries/boats.sql
PostgreSQL · db/queries/boats.sql
1-- sgl.query(AddSkipper, exec)
1-- sgl.query(AddSkipper, exec)
2INSERT INTO skippers (name, licence) VALUES (?, ?);
2INSERT INTO skippers (name, licence) VALUES ($1, $2);
AddBoatdiffers
SQLite · db/queries/boats.sql
PostgreSQL · db/queries/boats.sql
1-- sgl.query(AddBoat, exec)
1-- sgl.query(AddBoat, exec)
2INSERT INTO boats (name, harbour_id, skipper_id) VALUES (?, ?, ?);
2INSERT INTO boats (name, harbour_id, skipper_id) VALUES ($1, $2, $3);
GetBoatdiffers
SQLite · db/queries/boats.sql
PostgreSQL · db/queries/boats.sql
1-- sgl.query(GetBoat, one)
1-- sgl.query(GetBoat, one)
2-- sgl.embed(harbours)
2-- sgl.embed(harbours)
3SELECT boats.id, boats.name, harbours.id, harbours.name, harbours.county
3SELECT boats.id, boats.name, harbours.id, harbours.name, harbours.county
4FROM boats
4FROM boats
5INNER JOIN harbours ON harbours.id = boats.harbour_id
5INNER JOIN harbours ON harbours.id = boats.harbour_id
6WHERE boats.id = ?;
6WHERE boats.id = $1;
ListCrewsidentical
SQLite · db/queries/boats.sql
PostgreSQL · db/queries/boats.sql
1-- sgl.query(ListCrews, many)
1-- sgl.query(ListCrews, many)
2-- sgl.embed(skippers)
2-- sgl.embed(skippers)
3SELECT boats.id, boats.name, skippers.id, skippers.name, skippers.licence
3SELECT boats.id, boats.name, skippers.id, skippers.name, skippers.licence
4FROM boats
4FROM boats
5LEFT JOIN skippers ON skippers.id = boats.skipper_id
5LEFT JOIN skippers ON skippers.id = boats.skipper_id
6ORDER BY boats.id;
6ORDER BY boats.id;

What sgl generates

AddHarbouridentical
SQLite
PostgreSQL
1func (queries *Queries) AddHarbour(ctx context.Context, params AddHarbourParams) error
1func (queries *Queries) AddHarbour(ctx context.Context, params AddHarbourParams) error
2
2
3type AddHarbourParams struct {
3type AddHarbourParams struct {
4 Name string
4 Name string
5 County string
5 County string
6}
6}
AddSkipperidentical
SQLite
PostgreSQL
1func (queries *Queries) AddSkipper(ctx context.Context, params AddSkipperParams) error
1func (queries *Queries) AddSkipper(ctx context.Context, params AddSkipperParams) error
2
2
3type AddSkipperParams struct {
3type AddSkipperParams struct {
4 Name string
4 Name string
5 Licence string
5 Licence string
6}
6}
AddBoatidentical
SQLite
PostgreSQL
1func (queries *Queries) AddBoat(ctx context.Context, params AddBoatParams) error
1func (queries *Queries) AddBoat(ctx context.Context, params AddBoatParams) error
2
2
3type AddBoatParams struct {
3type AddBoatParams struct {
4 Name string
4 Name string
5 HarbourID int64
5 HarbourID int64
6 SkipperID *int64
6 SkipperID *int64
7}
7}
GetBoatidentical
SQLite
PostgreSQL
1func (queries *Queries) GetBoat(ctx context.Context, id int64) (GetBoatRow, error)
1func (queries *Queries) GetBoat(ctx context.Context, id int64) (GetBoatRow, error)
2
2
3type GetBoatRow struct {
3type GetBoatRow struct {
4 ID int64 `json:"id"`
4 ID int64 `json:"id"`
5 Name string `json:"name"`
5 Name string `json:"name"`
6 Harbours GetBoatHarbours
6 Harbours GetBoatHarbours
7}
7}
8
8
9type GetBoatHarbours struct {
9type GetBoatHarbours struct {
10 ID int64 `json:"id"`
10 ID int64 `json:"id"`
11 Name string `json:"name"`
11 Name string `json:"name"`
12 County string `json:"county"`
12 County string `json:"county"`
13}
13}
ListCrewsidentical
SQLite
PostgreSQL
1func (queries *Queries) ListCrews(ctx context.Context) ([]ListCrewsRow, error)
1func (queries *Queries) ListCrews(ctx context.Context) ([]ListCrewsRow, error)
2
2
3type ListCrewsRow struct {
3type ListCrewsRow struct {
4 ID int64 `json:"id"`
4 ID int64 `json:"id"`
5 Name string `json:"name"`
5 Name string `json:"name"`
6 Skippers *ListCrewsSkippers
6 Skippers *ListCrewsSkippers
7}
7}
8
8
9type ListCrewsSkippers struct {
9type ListCrewsSkippers struct {
10 ID *int64 `json:"id"`
10 ID *int64 `json:"id"`
11 Name *string `json:"name"`
11 Name *string `json:"name"`
12 Licence *string `json:"licence"`
12 Licence *string `json:"licence"`
13}
13}

The program

example.godiffers
SQLite
PostgreSQL
1package main
1package main
2
2
3import (
3import (
4 "context"
4 "context"
5 "database/sql"
5 "database/sql"
6 "fmt"
6 "fmt"
7 "io"
7 "io"
8
8
9 "seagull.sh/seagull/examples/sqlite/015_embed/internal/store"
9 "seagull.sh/seagull/examples/postgres/015_embed/internal/store"
10)
10)
11
11
12// run adds a small fleet and reads it back with joined tables as nested structs.
12// run adds a small fleet and reads it back with joined tables as nested structs.
13// sgl.embed(table) gathers the columns the query selects from that table into a field
13// sgl.embed(table) gathers the columns the query selects from that table into a field
14// named after the table, here Harbours and Skippers, with its own struct type named after
14// named after the table, here Harbours and Skippers, with its own struct type named after
15// the query and the table, such as GetBoatHarbours.
15// the query and the table, such as GetBoatHarbours.
16//
16//
17// GetBoat uses an INNER JOIN, so every boat has a harbour and Harbours is a value.
17// GetBoat uses an INNER JOIN, so every boat has a harbour and Harbours is a value.
18// ListCrews uses a LEFT JOIN, so a boat may have no skipper: Skippers is a pointer that
18// ListCrews uses a LEFT JOIN, so a boat may have no skipper: Skippers is a pointer that
19// is nil when the joined row is missing, and its fields are pointers too, as each column
19// is nil when the joined row is missing, and its fields are pointers too, as each column
20// of a LEFT JOIN can be NULL.
20// of a LEFT JOIN can be NULL.
21//
21//
22// Takes database (*sql.DB) which is a migrated database.
22// Takes database (*sql.DB) which is a migrated database.
23// Takes output (io.Writer) which receives the boat and the crew list.
23// Takes output (io.Writer) which receives the boat and the crew list.
24//
24//
25// Returns error when a query fails.
25// Returns error when a query fails.
26func run(ctx context.Context, database *sql.DB, output io.Writer) error {
26func run(ctx context.Context, database *sql.DB, output io.Writer) error {
27 queries := store.New(database)
27 queries := store.New(database)
28
28
29 if err := queries.AddHarbour(ctx, store.AddHarbourParams{Name: "Newlyn", County: "Cornwall"}); err != nil {
29 if err := queries.AddHarbour(ctx, store.AddHarbourParams{Name: "Newlyn", County: "Cornwall"}); err != nil {
30 return fmt.Errorf("adding a harbour: %w", err)
30 return fmt.Errorf("adding a harbour: %w", err)
31 }
31 }
32 if err := queries.AddSkipper(ctx, store.AddSkipperParams{Name: "Morwenna Penrose", Licence: "MCA-1182"}); err != nil {
32 if err := queries.AddSkipper(ctx, store.AddSkipperParams{Name: "Morwenna Penrose", Licence: "MCA-1182"}); err != nil {
33 return fmt.Errorf("adding a skipper: %w", err)
33 return fmt.Errorf("adding a skipper: %w", err)
34 }
34 }
35 boats := []store.AddBoatParams{
35 boats := []store.AddBoatParams{
36 {Name: "Kittiwake", HarbourID: 1, SkipperID: new(int64(1))},
36 {Name: "Kittiwake", HarbourID: 1, SkipperID: new(int64(1))},
37 {Name: "Salty Chip", HarbourID: 1, SkipperID: nil},
37 {Name: "Salty Chip", HarbourID: 1, SkipperID: nil},
38 }
38 }
39 for _, boat := range boats {
39 for _, boat := range boats {
40 if err := queries.AddBoat(ctx, boat); err != nil {
40 if err := queries.AddBoat(ctx, boat); err != nil {
41 return fmt.Errorf("adding %s: %w", boat.Name, err)
41 return fmt.Errorf("adding %s: %w", boat.Name, err)
42 }
42 }
43 }
43 }
44
44
45 boat, err := queries.GetBoat(ctx, 2)
45 boat, err := queries.GetBoat(ctx, 2)
46 if err != nil {
46 if err != nil {
47 return fmt.Errorf("getting boat 2: %w", err)
47 return fmt.Errorf("getting boat 2: %w", err)
48 }
48 }
49 fmt.Fprintf(output, "%s is moored at %s, %s\n", boat.Name, boat.Harbours.Name, boat.Harbours.County)
49 fmt.Fprintf(output, "%s is moored at %s, %s\n", boat.Name, boat.Harbours.Name, boat.Harbours.County)
50
50
51 crews, err := queries.ListCrews(ctx)
51 crews, err := queries.ListCrews(ctx)
52 if err != nil {
52 if err != nil {
53 return fmt.Errorf("listing crews: %w", err)
53 return fmt.Errorf("listing crews: %w", err)
54 }
54 }
55 for _, crew := range crews {
55 for _, crew := range crews {
56 if crew.Skippers == nil {
56 if crew.Skippers == nil {
57 fmt.Fprintf(output, "%s has no skipper\n", crew.Name)
57 fmt.Fprintf(output, "%s has no skipper\n", crew.Name)
58 continue
58 continue
59 }
59 }
60 fmt.Fprintf(output, "%s is skippered by %s, licence %s\n", crew.Name, *crew.Skippers.Name, *crew.Skippers.Licence)
60 fmt.Fprintf(output, "%s is skippered by %s, licence %s\n", crew.Name, *crew.Skippers.Name, *crew.Skippers.Licence)
61 }
61 }
62 return nil
62 return nil
63}
63}

Go type differences

The same SQL types map to different Go types, because each database reports them differently.

QueryFieldSQLitePostgreSQL
ListCrewscolumn id*int64int64
ListCrewscolumn name*stringstring