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Architecture

Purpose

The postgres adapter provides storage.Conn and ddl.Compiler implementations for PostgreSQL.

  • OpCopyColumn → UPDATE … SET dest = src WHERE dest IS NULL AND src IS NOT NULL It now also supports opening a pg_dump archive as a read-only ddl.Snapshot via postgres.Backups.

Components

  • PostgresAdapter: The core adapter implementing storage.Conn and ddl.Compiler.
  • Backups: A factory for opening pg_dump archives (ddl.BackupFormat).
  • snapshot: A restored archive answering ddl.Snapshot. It wraps PostgresAdapter to reuse schema introspection (Tables, Columns) and cast all column values to text during ReadTable.

Flows

  • OpenBackup: When opening a backup, the adapter creates a temporary database (snapshot_<nano>), restores the archive into it using pg_restore (with --no-owner --no-acl), connects to the restored database, and returns a snapshot.
  • Close: The snapshot closes the connection and forcefully drops the temporary database.

Decisions

  • restore then read with SQL; never parse the custom format: To read a pg_dump -Fc archive, we leverage pg_restore to dump it into a temporary database rather than trying to parse the complex binary custom format directly. This is the documented and reliable way to read custom format archives.