snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/real-world-examples/synchronizing-databases/mysql.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/ThreeDotsLabs/watermill"
+	"github.com/ThreeDotsLabs/watermill-sql/v4/pkg/sql"
+	"github.com/ThreeDotsLabs/watermill/message"
+)
+
+type mysqlUser struct {
+	ID        int64
+	User      string
+	FirstName string
+	LastName  string
+	CreatedAt time.Time
+}
+
+type mysqlSchemaAdapter struct {
+	sql.DefaultMySQLSchema
+}
+
+func (m mysqlSchemaAdapter) SchemaInitializingQueries(params sql.SchemaInitializingQueriesParams) ([]sql.Query, error) {
+	createQuery := `
+		CREATE TABLE IF NOT EXISTS ` + params.Topic + ` (
+			id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
+			user VARCHAR(36) NOT NULL,
+			first_name VARCHAR(36) NOT NULL,
+			last_name VARCHAR(36) NOT NULL,
+			created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+		);
+	`
+
+	return []sql.Query{{Query: createQuery}}, nil
+}
+
+func (m mysqlSchemaAdapter) InsertQuery(params sql.InsertQueryParams) (sql.Query, error) {
+	insertQuery := fmt.Sprintf(
+		`INSERT INTO %s (user, first_name, last_name, created_at) VALUES %s`,
+		params.Topic,
+		strings.TrimRight(strings.Repeat(`(?,?,?,?),`, len(params.Msgs)), ","),
+	)
+
+	var args []interface{}
+	for _, msg := range params.Msgs {
+		user := mysqlUser{}
+
+		decoder := gob.NewDecoder(bytes.NewBuffer(msg.Payload))
+		err := decoder.Decode(&user)
+		if err != nil {
+			return sql.Query{}, err
+		}
+
+		args = append(args, user.User, user.FirstName, user.LastName, user.CreatedAt)
+	}
+
+	return sql.Query{Query: insertQuery, Args: args}, nil
+}
+
+func (m mysqlSchemaAdapter) SelectQuery(params sql.SelectQueryParams) (sql.Query, error) {
+	nextOffsetQuery, err := params.OffsetsAdapter.NextOffsetQuery(sql.NextOffsetQueryParams{
+		Topic:         params.Topic,
+		ConsumerGroup: params.ConsumerGroup,
+	})
+	if err != nil {
+		return sql.Query{}, err
+	}
+
+	selectQuery := `
+		SELECT id, user, first_name, last_name, created_at FROM ` + params.Topic + `
+		WHERE
+			id > (` + nextOffsetQuery.Query + `)
+		ORDER BY
+			id ASC
+		LIMIT 1`
+
+	return sql.Query{Query: selectQuery, Args: nextOffsetQuery.Args}, nil
+}
+
+func (m mysqlSchemaAdapter) UnmarshalMessage(params sql.UnmarshalMessageParams) (_ sql.Row, err error) {
+	user := mysqlUser{}
+	err = params.Row.Scan(&user.ID, &user.User, &user.FirstName, &user.LastName, &user.CreatedAt)
+	if err != nil {
+		return sql.Row{}, err
+	}
+
+	var payload bytes.Buffer
+	encoder := gob.NewEncoder(&payload)
+
+	err = encoder.Encode(user)
+	if err != nil {
+		return sql.Row{}, err
+	}
+
+	msg := message.NewMessage(watermill.NewULID(), payload.Bytes())
+
+	return sql.Row{
+		Offset: user.ID,
+		Msg:    msg,
+	}, nil
+}