Compare · 020

Rows back from INSERT, UPDATE and DELETE: PostgreSQL and MariaDB

Every file of the PostgreSQL and MariaDB versions side by side, with the lines that differ marked. 3 parameter or column types differ in Go.

Compare PostgreSQL withSQLiteCockroachDBTimescaleDBMariaDBDuckDB

Configuration

sgl.yamldiffers
PostgreSQL
MariaDB
1version: 1
1version: 1
2
2
3databases:
3databases:
4 - name: orders
4 - name: orders
5 dialect: postgres
5 dialect: mariadb
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
12 migrate:
13 dsn: ${env:DATABASE_URL}

Migrations

db/migrations/0001_orders.up.sqldiffers
PostgreSQL
MariaDB
1CREATE TABLE orders (
1CREATE TABLE orders (
2 id BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
2 id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
3 item TEXT NOT NULL,
3 item VARCHAR(50) NOT NULL,
4 quantity BIGINT NOT NULL DEFAULT 1,
4 quantity INT NOT NULL DEFAULT 1,
5 status TEXT NOT NULL DEFAULT 'waiting'
5 status VARCHAR(20) NOT NULL DEFAULT 'waiting'
6);
6);
db/migrations/0001_orders.down.sqlidentical
PostgreSQL
MariaDB
1DROP TABLE orders;
1DROP TABLE orders;

Queries

PlaceOrderdiffers
PostgreSQL · db/queries/orders.sql
MariaDB · db/queries/orders.sql
1-- sgl.query(PlaceOrder, one)
1-- sgl.query(PlaceOrder, one)
2INSERT INTO orders (item, quantity) VALUES ($1, $2)
2INSERT INTO orders (item, quantity) VALUES (?, ?)
3RETURNING id, status, quantity * 250 AS price_pence;
3RETURNING id, status, quantity * 250 AS price_pence;
ServeWaitingOrdersdiffers
PostgreSQL · db/queries/orders.sql
MariaDB · db/queries/orders.sql
1-- sgl.query(ServeWaitingOrders, many, row: OrderLine)
1-- sgl.query(ServeWaitingOrders, execrows)
2UPDATE orders SET status = 'served' WHERE status = 'waiting'
2UPDATE orders SET status = 'served' WHERE status = 'waiting';
3RETURNING id, item, quantity;
CancelOrderdiffers
PostgreSQL · db/queries/orders.sql
MariaDB · db/queries/orders.sql
1-- sgl.query(CancelOrder, one, row: OrderLine)
1-- sgl.query(CancelOrder, one)
2DELETE FROM orders WHERE id = $1 AND status = 'waiting'
2DELETE FROM orders WHERE id = ? AND status = 'waiting'
3RETURNING id, item, quantity;
3RETURNING item, quantity;
ReopenOrderonly PostgreSQL
PostgreSQL · db/queries/orders.sql
MariaDB · not in this version
1-- sgl.query(ReopenOrder, one, model: orders)
2UPDATE orders SET status = 'waiting' WHERE id = $1
3RETURNING *;
ServedOrdersonly MariaDB
PostgreSQL · not in this version
MariaDB · db/queries/orders.sql
1-- sgl.query(ServedOrders, many)
2SELECT id, item, quantity FROM orders WHERE status = 'served' ORDER BY id;

What sgl generates

PlaceOrderdiffers
PostgreSQL
MariaDB
1func (queries *Queries) PlaceOrder(ctx context.Context, params PlaceOrderParams) (PlaceOrderRow, error)
1func (queries *Queries) PlaceOrder(ctx context.Context, params PlaceOrderParams) (PlaceOrderRow, error)
2
2
3type PlaceOrderParams struct {
3type PlaceOrderParams struct {
4 Item string
4 Item string
5 Quantity int64
5 Quantity int32
6}
6}
7
7
8type PlaceOrderRow struct {
8type PlaceOrderRow struct {
9 ID int64 `json:"id"`
9 ID int64 `json:"id"`
10 Status string `json:"status"`
10 Status string `json:"status"`
11 PricePence int64 `json:"price_pence"`
11 PricePence int32 `json:"price_pence"`
12}
12}
ServeWaitingOrdersdiffers
PostgreSQL
MariaDB
1func (queries *Queries) ServeWaitingOrders(ctx context.Context) ([]OrderLine, error)
1func (queries *Queries) ServeWaitingOrders(ctx context.Context) (int64, error)
2
3type OrderLine struct {
4 ID int64 `json:"id"`
5 Item string `json:"item"`
6 Quantity int64 `json:"quantity"`
7}
CancelOrderdiffers
PostgreSQL
MariaDB
1func (queries *Queries) CancelOrder(ctx context.Context, id int64) (OrderLine, error)
1func (queries *Queries) CancelOrder(ctx context.Context, id int64) (CancelOrderRow, error)
2
2
3type OrderLine struct {
3type CancelOrderRow struct {
4 ID int64 `json:"id"`
5 Item string `json:"item"`
4 Item string `json:"item"`
6 Quantity int64 `json:"quantity"`
5 Quantity int32 `json:"quantity"`
7}
6}
ReopenOrderonly PostgreSQL
PostgreSQL
MariaDB · not in this version
1func (queries *Queries) ReopenOrder(ctx context.Context, id int64) (Orders, error)
2
3type Orders struct {
4 ID int64 `json:"id"`
5 Item string `json:"item"`
6 Quantity int64 `json:"quantity"`
7 Status string `json:"status"`
8}
ServedOrdersonly MariaDB
PostgreSQL · not in this version
MariaDB
1func (queries *Queries) ServedOrders(ctx context.Context) ([]ServedOrdersRow, error)
2
3type ServedOrdersRow struct {
4 ID int64 `json:"id"`
5 Item string `json:"item"`
6 Quantity int32 `json:"quantity"`
7}

The program

example.godiffers
PostgreSQL
MariaDB
1package main
1package main
2
2
3import (
3import (
4 "cmp"
5 "context"
4 "context"
6 "database/sql"
5 "database/sql"
7 "errors"
6 "errors"
8 "fmt"
7 "fmt"
9 "io"
8 "io"
10 "slices"
11
9
12 "seagull.sh/seagull/examples/postgres/020_returning/internal/store"
10 "seagull.sh/seagull/examples/mariadb/020_returning/internal/store"
13)
11)
14
12
15// run places three orders, cancels one, serves the rest, tries to cancel an order that
13// run places three orders, cancels one, serves the rest and then tries to cancel an order
16// has already been served and reopens one. Every write uses RETURNING, so the rows it
14// that has already been served. The INSERT and the DELETE use RETURNING, so the rows they
17// touched come back from the same statement.
15// touched come back from the same statement.
18//
16//
19// A query reads its rows into a struct of its own, such as PlaceOrderRow, unless its
20// header names another. ServeWaitingOrders and CancelOrder return the same three columns,
21// so both name the row type OrderLine with row: OrderLine, and the generated code
22// declares that struct once for the two. ReopenOrder returns the whole order with
23// RETURNING *, so model: orders reads it into Orders, the table's model in models.go,
24// rather than a ReopenOrderRow with the same fields.
25//
26// Takes database (*sql.DB) which is a migrated database.
17// Takes database (*sql.DB) which is a migrated database.
27// Takes output (io.Writer) which receives what each write returned.
18// Takes output (io.Writer) which receives what each write returned.
28//
19//
29// Returns error when a query fails.
20// Returns error when a query fails.
30func run(ctx context.Context, database *sql.DB, output io.Writer) error {
21func run(ctx context.Context, database *sql.DB, output io.Writer) error {
31 queries := store.New(database)
22 queries := store.New(database)
32
23
33 // PlaceOrder is an INSERT declared as one: the id the identity column assigned, the
24 // PlaceOrder is an INSERT declared as one: the id MariaDB assigned, the default status
34 // default status and a computed price all come back in a PlaceOrderRow.
25 // and a computed price all come back in a PlaceOrderRow.
35 orders := []store.PlaceOrderParams{
26 orders := []store.PlaceOrderParams{
36 {Item: "chips", Quantity: 2},
27 {Item: "chips", Quantity: 2},
37 {Item: "battered cod", Quantity: 1},
28 {Item: "battered cod", Quantity: 1},
38 {Item: "mushy peas", Quantity: 1},
29 {Item: "mushy peas", Quantity: 1},
39 }
30 }
40 for _, order := range orders {
31 for _, order := range orders {
41 placed, err := queries.PlaceOrder(ctx, order)
32 placed, err := queries.PlaceOrder(ctx, order)
42 if err != nil {
33 if err != nil {
43 return fmt.Errorf("placing an order for %s: %w", order.Item, err)
34 return fmt.Errorf("placing an order for %s: %w", order.Item, err)
44 }
35 }
45 fmt.Fprintf(output, "placed #%d %-12s %s, %dp\n", placed.ID, order.Item, placed.Status, placed.PricePence)
36 fmt.Fprintf(output, "placed #%d %-12s %s, %dp\n", placed.ID, order.Item, placed.Status, placed.PricePence)
46 }
37 }
47
38
48 // CancelOrder is a DELETE declared as one, so it returns the row it removed.
39 // CancelOrder is a DELETE declared as one, so it returns the row it removed.
49 cancelled, err := queries.CancelOrder(ctx, 2)
40 cancelled, err := queries.CancelOrder(ctx, 2)
50 if err != nil {
41 if err != nil {
51 return fmt.Errorf("cancelling order 2: %w", err)
42 return fmt.Errorf("cancelling order 2: %w", err)
52 }
43 }
53 fmt.Fprintf(output, "cancelled #2 %-12s x%d\n", cancelled.Item, cancelled.Quantity)
44 fmt.Fprintf(output, "cancelled #2 %-12s x%d\n", cancelled.Item, cancelled.Quantity)
54
45
55 // ServeWaitingOrders is an UPDATE declared as many: one row for every order it changed.
46 // MariaDB has RETURNING on INSERT, REPLACE and DELETE, but not on UPDATE, so
56 // PostgreSQL does not promise an order for RETURNING rows, so sort them.
47 // ServeWaitingOrders is execrows and ServedOrders reads the changed rows back.
57 served, err := queries.ServeWaitingOrders(ctx)
48 if _, err := queries.ServeWaitingOrders(ctx); err != nil {
58 if err != nil {
59 return fmt.Errorf("serving orders: %w", err)
49 return fmt.Errorf("serving orders: %w", err)
60 }
50 }
61 slices.SortFunc(served, func(a, b store.OrderLine) int { return cmp.Compare(a.ID, b.ID) })
51 served, err := queries.ServedOrders(ctx)
52 if err != nil {
53 return fmt.Errorf("listing served orders: %w", err)
54 }
62 for _, order := range served {
55 for _, order := range served {
63 fmt.Fprintf(output, "served #%d %-12s x%d\n", order.ID, order.Item, order.Quantity)
56 fmt.Fprintf(output, "served #%d %-12s x%d\n", order.ID, order.Item, order.Quantity)
64 }
57 }
65
58
66 // A one query that matches no row returns sql.ErrNoRows, writes included: order 1 has
59 // A one query that matches no row returns sql.ErrNoRows, writes included: order 1 has
67 // been served, so the DELETE's WHERE clause no longer matches it.
60 // been served, so the DELETE's WHERE clause no longer matches it.
68 _, err = queries.CancelOrder(ctx, 1)
61 _, err = queries.CancelOrder(ctx, 1)
69 switch {
62 if errors.Is(err, sql.ErrNoRows) {
70 case errors.Is(err, sql.ErrNoRows):
71 fmt.Fprintln(output, "cannot cancel #1: it is no longer waiting")
63 fmt.Fprintln(output, "cannot cancel #1: it is no longer waiting")
72 case err != nil:
64 return nil
73 return fmt.Errorf("cancelling order 1: %w", err)
74 default:
75 return errors.New("cancelled an order that had already been served")
76 }
65 }
77
78 reopened, err := queries.ReopenOrder(ctx, 3)
79 if err != nil {
66 if err != nil {
80 return fmt.Errorf("reopening order 3: %w", err)
67 return fmt.Errorf("cancelling order 1: %w", err)
81 }
68 }
82 fmt.Fprintf(output, "reopened #%d %-12s x%d, %s\n", reopened.ID, reopened.Item, reopened.Quantity, reopened.Status)
69 return errors.New("cancelled an order that had already been served")
83 return nil
84}
70}

Go type differences

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

QueryFieldPostgreSQLMariaDB
PlaceOrderparameter quantityint64int32
PlaceOrdercolumn price_penceint64int32
CancelOrdercolumn quantityint64int32