Compare · 005

From SQL types to Go types: MySQL and TimescaleDB

Every file of the MySQL and TimescaleDB 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
MySQL
TimescaleDB
1version: 1
1version: 1
2
2
3databases:
3databases:
4 - name: landings
4 - name: landings
5 dialect: mysql
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_landings.up.sqldiffers
MySQL
TimescaleDB
1CREATE TABLE landings (
1CREATE TABLE landings (
2 id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
2 id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
3 species VARCHAR(50) NOT NULL,
3 catch_id UUID NOT NULL,
4 boxes SMALLINT NOT NULL,
4 species TEXT NOT NULL,
5 fish INT NOT NULL,
5 boxes SMALLINT NOT NULL,
6 weight_g BIGINT NOT NULL,
6 fish INTEGER NOT NULL,
7 length_cm DOUBLE NOT NULL,
7 weight_g BIGINT NOT NULL,
8 on_ice BOOLEAN NOT NULL,
8 length_cm REAL NOT NULL,
9 landed_at DATETIME NOT NULL,
9 sea_temp DOUBLE PRECISION NOT NULL,
10 tag VARBINARY(16) NOT NULL,
10 price NUMERIC(8, 2) NOT NULL,
11 notes TEXT,
11 on_ice BOOLEAN NOT NULL,
12 berth TINYINT UNSIGNED NOT NULL,
12 landed_on DATE NOT NULL,
13 price_per_kg DECIMAL(6, 2) NOT NULL
13 landed_at TIMESTAMPTZ NOT NULL,
14 harbour_ip INET NOT NULL,
15 tag BYTEA NOT NULL,
16 notes TEXT
14);
17);
db/migrations/0001_landings.down.sqlidentical
MySQL
TimescaleDB
1DROP TABLE landings;
1DROP TABLE landings;

Queries

RecordLandingdiffers
MySQL · db/queries/landings.sql
TimescaleDB · db/queries/landings.sql
1-- sgl.query(RecordLanding, execresult)
1-- sgl.query(RecordLanding, one)
2-- ?11 as sgl.param(price_per_kg, type: text)
2INSERT INTO landings (catch_id, species, boxes, fish, weight_g, length_cm, sea_temp, price, on_ice, landed_on, landed_at, harbour_ip, tag, notes)
3INSERT INTO landings (species, boxes, fish, weight_g, length_cm, on_ice, landed_at, tag, notes, berth, price_per_kg)
3VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
4VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?);
4RETURNING id;
GetLandingdiffers
MySQL · db/queries/landings.sql
TimescaleDB · db/queries/landings.sql
1-- sgl.query(GetLanding, one)
1-- sgl.query(GetLanding, one)
2SELECT id, species, boxes, fish, weight_g, length_cm, on_ice, landed_at, tag, notes, berth, price_per_kg
2SELECT id, catch_id, species, boxes, fish, weight_g, length_cm, sea_temp, price, on_ice, landed_on, landed_at, harbour_ip, tag, notes
3FROM landings
3FROM landings
4WHERE id = ?;
4WHERE id = $1;

What sgl generates

RecordLandingdiffers
MySQL
TimescaleDB
1func (queries *Queries) RecordLanding(ctx context.Context, params RecordLandingParams) (sql.Result, error)
1func (queries *Queries) RecordLanding(ctx context.Context, params RecordLandingParams) (RecordLandingRow, error)
2
2
3type RecordLandingParams struct {
3type RecordLandingParams struct {
4 Species string
4 CatchID uuid.UUID
5 Boxes int16
5 Species string
6 Fish int32
6 Boxes int16
7 WeightG int64
7 Fish int32
8 LengthCm float64
8 WeightG int64
9 OnIce bool
9 LengthCm float32
10 LandedAt time.Time
10 SeaTemp float64
11 Tag []byte
11 Price apd.Decimal
12 Notes *string
12 OnIce bool
13 Berth uint8
13 LandedOn time.Time
14 PricePerKg string
14 LandedAt time.Time
15 HarbourIP any
16 Tag []byte
17 Notes *string
15}
18}
19
20type RecordLandingRow struct {
21 ID int64 `json:"id"`
22}
GetLandingdiffers
MySQL
TimescaleDB
1func (queries *Queries) GetLanding(ctx context.Context, id int64) (GetLandingRow, error)
1func (queries *Queries) GetLanding(ctx context.Context, id int64) (GetLandingRow, error)
2
2
3type GetLandingRow struct {
3type GetLandingRow struct {
4 ID int64 `json:"id"`
4 ID int64 `json:"id"`
5 Species string `json:"species"`
5 CatchID uuid.UUID `json:"catch_id"`
6 Boxes int16 `json:"boxes"`
6 Species string `json:"species"`
7 Fish int32 `json:"fish"`
7 Boxes int16 `json:"boxes"`
8 WeightG int64 `json:"weight_g"`
8 Fish int32 `json:"fish"`
9 LengthCm float64 `json:"length_cm"`
9 WeightG int64 `json:"weight_g"`
10 OnIce bool `json:"on_ice"`
10 LengthCm float32 `json:"length_cm"`
11 LandedAt time.Time `json:"landed_at"`
11 SeaTemp float64 `json:"sea_temp"`
12 Tag []byte `json:"tag"`
12 Price apd.Decimal `json:"price"`
13 Notes *string `json:"notes"`
13 OnIce bool `json:"on_ice"`
14 Berth uint8 `json:"berth"`
14 LandedOn time.Time `json:"landed_on"`
15 PricePerKg apd.Decimal `json:"price_per_kg"`
15 LandedAt time.Time `json:"landed_at"`
16 HarbourIP any `json:"harbour_ip"`
17 Tag []byte `json:"tag"`
18 Notes *string `json:"notes"`
16}
19}

The program

example.godiffers
MySQL
TimescaleDB
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 "time"
8 "time"
9
9
10 "seagull.sh/seagull/examples/mysql/005_type_mapping/internal/store"
10 "github.com/cockroachdb/apd/v3"
11 "github.com/google/uuid"
12
13 "seagull.sh/seagull/examples/postgres/005_type_mapping/internal/store"
11)
14)
12
15
13// run records a landing of fish and reads it back, printing the Go type sgl chose for
16// run records a landing of fish and reads it back, printing the Go type sgl chose for
14// each column. Seagull maps the type each column declares in db/migrations: SMALLINT, INT
17// each column of db/migrations. PostgreSQL's types are exact, so each maps by name:
15// and BIGINT give int16, int32 and int64, and an UNSIGNED integer gives the unsigned Go
16// type of the same width, so TINYINT UNSIGNED is uint8. DOUBLE gives float64, BOOLEAN
17// (MySQL's TINYINT(1)) gives bool, DATETIME gives time.Time when the DSN sets
18// parseTime=true, and VARBINARY gives []byte.
19//
18//
20// DECIMAL gives apd.Decimal from github.com/cockroachdb/apd/v3, which holds the exact
19// - SMALLINT, INTEGER and BIGINT give int16, int32 and int64;
21// value. The insert binds the price as text instead, through sgl.param(price_per_kg,
20// - REAL is single precision and gives float32, while DOUBLE PRECISION gives float64;
22// type: text), and MySQL converts "4.20" to DECIMAL(6, 2) without rounding.
21// - NUMERIC gives apd.Decimal from github.com/cockroachdb/apd/v3, which keeps money
22// exact, and UUID gives uuid.UUID from github.com/google/uuid;
23// - DATE and TIMESTAMPTZ give time.Time, and BYTEA gives []byte;
24// - a type Seagull has no mapping for, such as INET, gives any, and the driver decides
25// what it holds: pgx's database/sql driver hands back the address as a string. Give
26// such a column a go_type override to pin it down.
23//
27//
24// Takes database (*sql.DB) which is a migrated database.
28// Takes database (*sql.DB) which is a migrated database.
25// Takes output (io.Writer) which receives one line per column.
29// Takes output (io.Writer) which receives one line per column.
26//
30//
27// Returns error when a query fails.
31// Returns error when a query fails.
28func run(ctx context.Context, database *sql.DB, output io.Writer) error {
32func run(ctx context.Context, database *sql.DB, output io.Writer) error {
29 queries := store.New(database)
33 queries := store.New(database)
30
34
31 result, err := queries.RecordLanding(ctx, store.RecordLandingParams{
35 recorded, err := queries.RecordLanding(ctx, store.RecordLandingParams{
32 Species: "mackerel",
36 CatchID: uuid.MustParse("6f1c0b8e-4b2a-4c55-9d7e-2a3f5e8c1d40"),
33 Boxes: 12,
37 Species: "mackerel",
34 Fish: 480,
38 Boxes: 12,
35 WeightG: 163_200,
39 Fish: 480,
36 LengthCm: 31.5,
40 WeightG: 163_200,
37 OnIce: true,
41 LengthCm: 31.5,
38 LandedAt: time.Date(2026, time.May, 1, 5, 30, 0, 0, time.UTC),
42 SeaTemp: 12.25,
39 Tag: []byte{0x04, 0xa2, 0x19, 0xf3},
43 Price: *apd.New(41_280, -2),
40 Notes: new("landed at Newlyn"),
44 OnIce: true,
41 Berth: 7,
45 LandedOn: time.Date(2026, time.May, 1, 0, 0, 0, 0, time.UTC),
42 PricePerKg: "4.20",
46 LandedAt: time.Date(2026, time.May, 1, 5, 30, 0, 0, time.UTC),
47 HarbourIP: "192.0.2.17",
48 Tag: []byte{0x04, 0xa2, 0x19, 0xf3},
49 Notes: new("landed at Newlyn"),
43 })
50 })
44 if err != nil {
51 if err != nil {
45 return fmt.Errorf("recording a landing: %w", err)
52 return fmt.Errorf("recording a landing: %w", err)
46 }
53 }
47 id, err := result.LastInsertId()
48 if err != nil {
49 return fmt.Errorf("reading the landing's id: %w", err)
50 }
51
54
52 landing, err := queries.GetLanding(ctx, id)
55 landing, err := queries.GetLanding(ctx, recorded.ID)
53 if err != nil {
56 if err != nil {
54 return fmt.Errorf("getting landing %d: %w", id, err)
57 return fmt.Errorf("getting landing %d: %w", recorded.ID, err)
55 }
58 }
56 fmt.Fprintf(output, "id %-12T %d\n", landing.ID, landing.ID)
59 fmt.Fprintf(output, "id %-12T %d\n", landing.ID, landing.ID)
57 fmt.Fprintf(output, "species %-12T %s\n", landing.Species, landing.Species)
60 fmt.Fprintf(output, "catch_id %-12T %s\n", landing.CatchID, landing.CatchID)
58 fmt.Fprintf(output, "boxes %-12T %d\n", landing.Boxes, landing.Boxes)
61 fmt.Fprintf(output, "species %-12T %s\n", landing.Species, landing.Species)
59 fmt.Fprintf(output, "fish %-12T %d\n", landing.Fish, landing.Fish)
62 fmt.Fprintf(output, "boxes %-12T %d\n", landing.Boxes, landing.Boxes)
60 fmt.Fprintf(output, "weight_g %-12T %d\n", landing.WeightG, landing.WeightG)
63 fmt.Fprintf(output, "fish %-12T %d\n", landing.Fish, landing.Fish)
61 fmt.Fprintf(output, "length_cm %-12T %.1f\n", landing.LengthCm, landing.LengthCm)
64 fmt.Fprintf(output, "weight_g %-12T %d\n", landing.WeightG, landing.WeightG)
62 fmt.Fprintf(output, "on_ice %-12T %t\n", landing.OnIce, landing.OnIce)
65 fmt.Fprintf(output, "length_cm %-12T %.1f\n", landing.LengthCm, landing.LengthCm)
63 fmt.Fprintf(output, "landed_at %-12T %s\n", landing.LandedAt, landing.LandedAt.Format(time.RFC3339))
66 fmt.Fprintf(output, "sea_temp %-12T %.2f\n", landing.SeaTemp, landing.SeaTemp)
67 fmt.Fprintf(output, "price %-12T %s\n", landing.Price, landing.Price.String())
68 fmt.Fprintf(output, "on_ice %-12T %t\n", landing.OnIce, landing.OnIce)
69 fmt.Fprintf(output, "landed_on %-12T %s\n", landing.LandedOn, landing.LandedOn.Format(time.DateOnly))
70 // TIMESTAMPTZ arrives in the connection's time zone, so print it in UTC.
71 fmt.Fprintf(output, "landed_at %-12T %s\n", landing.LandedAt, landing.LandedAt.UTC().Format(time.RFC3339))
72 fmt.Fprintf(output, "harbour_ip %-12T %v\n", landing.HarbourIP, landing.HarbourIP)
64 // %T prints []byte as []uint8, since byte is an alias for uint8.
73 // %T prints []byte as []uint8, since byte is an alias for uint8.
65 fmt.Fprintf(output, "tag %-12T % x\n", landing.Tag, landing.Tag)
74 fmt.Fprintf(output, "tag %-12T % x\n", landing.Tag, landing.Tag)
66 fmt.Fprintf(output, "notes %-12T %s\n", landing.Notes, *landing.Notes)
75 fmt.Fprintf(output, "notes %-12T %s\n", landing.Notes, *landing.Notes)
67 fmt.Fprintf(output, "berth %-12T %d\n", landing.Berth, landing.Berth)
68 fmt.Fprintf(output, "price_per_kg %-12T %s\n", landing.PricePerKg, landing.PricePerKg.String())
69 return nil
76 return nil
70}
77}

Go type differences

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

QueryFieldMySQLTimescaleDB
RecordLandingparameter length_cmfloat64float32
GetLandingcolumn length_cmfloat64float32