F.28. pg_logicalinspect — logical decoding components inspection
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## F.28. pg_logicalinspect — logical decoding components inspection #

The `pg_logicalinspect` module provides SQL functions that allow you to inspect the contents of logical decoding components. It allows the inspection of serialized logical snapshots of a running PostgreSQL database cluster, which is useful for debugging or educational purposes.

By default, use of these functions is restricted to superusers and members of the `pg_read_server_files` role. Access may be granted by superusers to others using `GRANT`.

### F.28.1. Functions #

`pg_get_logical_snapshot_meta(filename text) returns record` #

  Gets logical snapshot metadata about a snapshot file that is located in the server's `pg_logical/snapshots` directory. The `filename` argument represents the snapshot file name. For example:

      postgres=# SELECT * FROM pg_ls_logicalsnapdir();
      -[ RECORD 1 ]+-----------------------
      name         | 0-40796E18.snap
      size         | 152
      modification | 2024-08-14 16:36:32+00

      postgres=# SELECT * FROM pg_get_logical_snapshot_meta('0-40796E18.snap');
      -[ RECORD 1 ]--------
      magic    | 1369563137
      checksum | 1028045905
      version  | 6

      postgres=# SELECT ss.name, meta.* FROM pg_ls_logicalsnapdir() AS ss,
      pg_get_logical_snapshot_meta(ss.name) AS meta;
      -[ RECORD 1 ]-------------
      name     | 0-40796E18.snap
      magic    | 1369563137
      checksum | 1028045905
      version  | 6

  If `filename` does not match a snapshot file, the function raises an error.

`pg_get_logical_snapshot_info(filename text) returns record` #

  Gets logical snapshot information about a snapshot file that is located in the server's `pg_logical/snapshots` directory. The `filename` argument represents the snapshot file name. For example:

      postgres=# SELECT * FROM pg_ls_logicalsnapdir();
      -[ RECORD 1 ]+-----------------------
      name         | 0-40796E18.snap
      size         | 152
      modification | 2024-08-14 16:36:32+00

      postgres=# SELECT * FROM pg_get_logical_snapshot_info('0-40796E18.snap');
      -[ RECORD 1 ]------------+-----------
      state                    | consistent
      xmin                     | 751
      xmax                     | 751
      start_decoding_at        | 0/40796AF8
      two_phase_at             | 0/40796AF8
      initial_xmin_horizon     | 0
      building_full_snapshot   | f
      in_slot_creation         | f
      last_serialized_snapshot | 0/00000000
      next_phase_at            | 0
      committed_count          | 0
      committed_xip            |
      catchange_count          | 2
      catchange_xip            | {751,752}

      postgres=# SELECT ss.name, info.* FROM pg_ls_logicalsnapdir() AS ss,
      pg_get_logical_snapshot_info(ss.name) AS info;
      -[ RECORD 1 ]------------+----------------
      name                     | 0-40796E18.snap
      state                    | consistent
      xmin                     | 751
      xmax                     | 751
      start_decoding_at        | 0/40796AF8
      two_phase_at             | 0/40796AF8
      initial_xmin_horizon     | 0
      building_full_snapshot   | f
      in_slot_creation         | f
      last_serialized_snapshot | 0/00000000
      next_phase_at            | 0
      committed_count          | 0
      committed_xip            |
      catchange_count          | 2
      catchange_xip            | {751,752}

  If `filename` does not match a snapshot file, the function raises an error.

### F.28.2. Author #

Bertrand Drouvot `<bertranddrouvot.pg@gmail.com>`

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