120 lines
2.8 KiB
Go
120 lines
2.8 KiB
Go
// Migration tooling
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//
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// Runs migrations in-order based on files found in the migration
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// root directory provided as argument.
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package main
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import (
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"bufio"
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"bytes"
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"log"
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"os"
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"path/filepath"
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)
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var commentPrefix = []byte("--")
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var requirementPrefix = []byte("requires:")
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// Applies a migration to the given database connection.
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//
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// If an error is returned while trying to read the migration file
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// or execute the SQL it contains, the error is returned.
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func ApplyMigration(db DB, migration Migration) error {
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migrationPath := migration.Path
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migrationBytes, err := os.ReadFile(migrationPath)
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if err != nil {
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return err
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}
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migrationSql := string(migrationBytes)
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log.Printf("SQL: %s", migrationSql)
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err = db.Execute(migrationSql)
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if err != nil {
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return err
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}
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return nil
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}
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// Removes the provided prefix from the byte slice and removes
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// any spaces leading or trailing the resulting slice.
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//
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// If the prefix is not present, nothing is removed except
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// the leading and trailing spaces.
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func cutPrefixAndTrim(b []byte, prefix []byte) []byte {
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withoutPrefix, _ := bytes.CutPrefix(b, prefix)
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return bytes.TrimSpace(withoutPrefix)
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}
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// Extracts any migration headers present in the migration source file.
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// Headers are left in comments of the form:
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// -- <header-name>: ...
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// Anything else than the known headers is ignored.
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func gatherMigrationHeaders(migrationFile *os.File) MigrationHeaders {
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scanner := bufio.NewScanner(migrationFile)
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requirements := []string{}
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for scanner.Scan() {
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currentBytes := scanner.Bytes()
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if !bytes.HasPrefix(currentBytes, commentPrefix) {
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continue
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}
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commentBytes := cutPrefixAndTrim(currentBytes, commentPrefix)
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if bytes.HasPrefix(commentBytes, requirementPrefix) {
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reqName := cutPrefixAndTrim(commentBytes, requirementPrefix)
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requirements = append(requirements, string(reqName))
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}
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}
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return MigrationHeaders{Requirements: requirements}
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}
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// Gathers available migrations from the migration root directory.
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//
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// Migrations are expected to be .sql files.
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func getMigrations(migrationsRoot string) ([]Migration, error) {
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files, err := os.ReadDir(migrationsRoot)
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if err != nil {
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log.Printf("Failed to read migration directory: %s", migrationsRoot)
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return []Migration{}, err
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}
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migrationGraph := NewMigrationGraph()
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for _, file := range files {
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filename := file.Name()
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if filepath.Ext(filename) != ".sql" {
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continue
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}
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migrationPath := filepath.Join(migrationsRoot, file.Name())
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file, _ := os.Open(migrationPath)
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headers := gatherMigrationHeaders(file)
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requirements := ""
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if len(headers.Requirements) > 0 {
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requirements = headers.Requirements[0]
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}
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migration := NewMigration(migrationPath, filepath.Base(file.Name()), requirements)
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migrationGraph.AddMigration(migration)
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}
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return migrationGraph.GetLinearHistory()
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}
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