Skip to content

Latest commit

 

History

History
123 lines (83 loc) · 3.87 KB

pgcopydb_snapshot.rst

File metadata and controls

123 lines (83 loc) · 3.87 KB
Raw

pgcopydb snapshot

pgcopydb snapshot - Create and export a snapshot on the source database

The command pgcopydb snapshot connects to the source database and executes a SQL query to export a snapshot. The obtained snapshot is both printed on stdout and also in a file where other pgcopydb commands might expect to find it.

pgcopydb snapshot: Create and export a snapshot on the source database
usage: pgcopydb snapshot  --source ...

  --source         Postgres URI to the source database
  --dir            Work directory to use
  --follow         Implement logical decoding to replay changes
  --plugin         Output plugin to use (test_decoding, wal2json)
  --slot-name      Use this Postgres replication slot name

Options

The following options are available to pgcopydb create and pgcopydb drop subcommands:

--source

Connection string to the source Postgres instance. See the Postgres documentation for connection strings__ for the details. In short both the quoted form "host=... dbname=..." and the URI form postgres://user@host:5432/dbname are supported.

__ https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING

--dir

During its normal operations pgcopydb creates a lot of temporary files to track sub-processes progress. Temporary files are created in the directory location given by this option, or defaults to ${TMPDIR}/pgcopydb when the environment variable is set, or then to /tmp/pgcopydb.

--follow

When the --follow option is used then pgcopydb implements Change Data Capture as detailed in the manual page for pgcopydb_follow in parallel to the main copy database steps.

The replication slot is created using the Postgres replication protocol command CREATE_REPLICATION_SLOT, which then exports the snapshot being used in that command.

--plugin

Logical decoding output plugin to use. The default is test_decoding__ which ships with Postgres core itself, so is probably already available on your source server.

It is possible to use wal2json__ instead. The support for wal2json is mostly historical in pgcopydb, it should not make a user visible difference whether you use the default test_decoding or wal2json.

__ https://www.postgresql.org/docs/current/test-decoding.html __ https://github.com/eulerto/wal2json/

--slot-name

Logical decoding slot name to use.

--verbose

Increase current verbosity. The default level of verbosity is INFO. In ascending order pgcopydb knows about the following verbosity levels: FATAL, ERROR, WARN, INFO, NOTICE, DEBUG, TRACE.

--debug

Set current verbosity to DEBUG level.

--trace

Set current verbosity to TRACE level.

--quiet

Set current verbosity to ERROR level.

Environment

PGCOPYDB_SOURCE_PGURI

Connection string to the source Postgres instance. When --source is ommitted from the command line, then this environment variable is used.

Examples

Create a snapshot on the source database in the background:

$ pgcopydb snapshot &
[1] 72938
17:31:52 72938 INFO  Running pgcopydb version 0.7.13.gcbf2d16.dirty from "/Users/dim/dev/PostgreSQL/pgcopydb/./src/bin/pgcopydb/pgcopydb"
17:31:52 72938 INFO  Using work dir "/var/folders/d7/zzxmgs9s16gdxxcm0hs0sssw0000gn/T//pgcopydb"
17:31:52 72938 INFO  Removing the stale pid file "/var/folders/d7/zzxmgs9s16gdxxcm0hs0sssw0000gn/T//pgcopydb/pgcopydb.aux.pid"
17:31:52 72938 INFO  Work directory "/var/folders/d7/zzxmgs9s16gdxxcm0hs0sssw0000gn/T//pgcopydb" already exists
17:31:52 72938 INFO  Exported snapshot "00000003-000CB5FE-1" from the source database
00000003-000CB5FE-1

And when the process is done, stop maintaining the snapshot in the background:

$ kill %1
17:31:56 72938 INFO  Asked to terminate, aborting
[1]+  Done                    pgcopydb snapshot