106 lines
2.0 KiB
Go
106 lines
2.0 KiB
Go
package storage
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import (
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"database/sql"
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"fmt"
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_ "github.com/lib/pq"
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)
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type Postgres struct {
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db *sql.DB
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}
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func NewPostgres(db *sql.DB) (*Postgres, error) {
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p := &Postgres{db: db}
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if err := p.migrate(pgMigration); err != nil {
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return &Postgres{}, err
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}
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return p, nil
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}
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var pgMigration = []string{
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`CREATE TABLE channel (
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id SERIAL PRIMARY KEY,
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url VARCHAR(255) NOT NULL,
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feed_url VARCHAR(255) NOT NULL,
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name VARCHAR(255) NOT NULL
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)`,
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`CREATE TABLE video (
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id SERIAL PRIMARY KEY,
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channel_id INTEGER REFERENCES channel(id) ON DELETE CASCADE,
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url VARCHAR(255) NOT NULL,
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title VARCHAR(255) NOT NULL,
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description TEXT,
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summary TEXT
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)`,
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}
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func (p *Postgres) migrate(wanted []string) error {
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query := `CREATE TABLE IF NOT EXISTS migration
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("id" SERIAL PRIMARY KEY, "query" TEXT)`
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_, err := p.db.Exec(query)
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if err != nil {
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return err
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}
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// find existing
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rows, err := p.db.Query(`SELECT query FROM migration ORDER BY id`)
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if err != nil {
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return err
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}
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existing := []string{}
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for rows.Next() {
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var query string
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if err := rows.Scan(&query); err != nil {
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return err
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}
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existing = append(existing, query)
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}
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rows.Close()
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// compare
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missing, err := compareMigrations(wanted, existing)
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if err != nil {
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return err
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}
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// execute missing
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for _, query := range missing {
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if _, err := p.db.Exec(query); err != nil {
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return err
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}
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// register
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if _, err := p.db.Exec(`
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INSERT INTO migration
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(query) VALUES ($1)
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`, query); err != nil {
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return err
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}
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}
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return nil
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}
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func compareMigrations(wanted, existing []string) ([]string, error) {
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needed := []string{}
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if len(wanted) < len(existing) {
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return []string{}, fmt.Errorf("not enough migrations")
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}
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for i, want := range wanted {
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switch {
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case i >= len(existing):
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needed = append(needed, want)
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case want == existing[i]:
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// do nothing
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case want != existing[i]:
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return []string{}, fmt.Errorf("incompatible migration: %v", want)
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}
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}
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return needed, nil
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}
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