DOKK / manpages / debian 12 / pgcopydb / pgcopydb dump.1.en
PGCOPYDB DUMP(1) pgcopydb PGCOPYDB DUMP(1)

pgcopydb dump - pgcopydb dump

pgcopydb dump - Dump database objects from a Postgres instance

This command prefixes the following sub-commands:

pgcopydb dump


  schema     Dump source database schema as custom files in target directory


  pre-data   Dump source database pre-data schema as custom files in target directory


  post-data  Dump source database post-data schema as custom files in target directory


  roles      Dump source database roles as custome file in work directory


pgcopydb dump schema - Dump source database schema as custom files in target directory

The command pgcopydb dump schema uses pg_dump to export SQL schema definitions from the given source Postgres instance.

pgcopydb dump schema: Dump source database schema as custom files in target directory
usage: pgcopydb dump schema  --source <URI> --target <dir>


  --source          Postgres URI to the source database


  --target          Directory where to save the dump files


  --dir             Work directory to use


  --snapshot        Use snapshot obtained with pg_export_snapshot


pgcopydb dump pre-data - Dump source database pre-data schema as custom files in target directory

The command pgcopydb dump pre-data uses pg_dump to export SQL schema pre-data definitions from the given source Postgres instance.

pgcopydb dump pre-data: Dump source database pre-data schema as custom files in target directory
usage: pgcopydb dump schema  --source <URI> --target <dir>


  --source          Postgres URI to the source database


  --target          Directory where to save the dump files


  --dir             Work directory to use


  --snapshot        Use snapshot obtained with pg_export_snapshot


pgcopydb dump post-data - Dump source database post-data schema as custom files in target directory

The command pgcopydb dump post-data uses pg_dump to export SQL schema post-data definitions from the given source Postgres instance.

pgcopydb dump post-data: Dump source database post-data schema as custom files in target directory
usage: pgcopydb dump schema  --source <URI> --target <dir>


  --source          Postgres URI to the source database


  --target          Directory where to save the dump files


  --dir             Work directory to use


  --snapshot        Use snapshot obtained with pg_export_snapshot


pgcopydb dump roles - Dump source database roles as custome file in work directory

The command pgcopydb dump roles uses pg_dumpall --roles-only to export SQL definitions of the roles found on the source Postgres instance.

pgcopydb dump roles: Dump source database roles as custome file in work directory
usage: pgcopydb dump roles  --source <URI>


  --source          Postgres URI to the source database


  --target          Directory where to save the dump files


  --dir             Work directory to use


The pg_dumpall --roles-only is used to fetch the list of roles from the source database, and this command includes support for passwords. As a result, this operation requires the superuser privileges.

The pgcopydb dump schema command implements the first step of the full database migration and fetches the schema definitions from the source database.

When the command runs, it calls pg_dump to get first the pre-data schema output in a Postgres custom file, and then again to get the post-data schema output in another Postgres custom file.

The output files are written to the schema sub-directory of the --target directory.

The pgcopydb dump pre-data and pgcopydb dump post-data are limiting their action to respectively the pre-data and the post-data sections of the pg_dump.

The following options are available to pgcopydb dump schema:

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.
Connection string to the target Postgres instance.
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.
Instead of exporting its own snapshot by calling the PostgreSQL function pg_export_snapshot() it is possible for pgcopydb to re-use an already exported snapshot.
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.
Set current verbosity to DEBUG level.
Set current verbosity to TRACE level.
Set current verbosity to ERROR level.

PGCOPYDB_SOURCE_PGURI

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


First, using pgcopydb dump schema

$ pgcopydb dump schema --source "port=5501 dbname=demo" --target /tmp/target
09:35:21 3926 INFO  Dumping database from "port=5501 dbname=demo"
09:35:21 3926 INFO  Dumping database into directory "/tmp/target"
09:35:21 3926 INFO  Found a stale pidfile at "/tmp/target/pgcopydb.pid"
09:35:21 3926 WARN  Removing the stale pid file "/tmp/target/pgcopydb.pid"
09:35:21 3926 INFO  Using pg_dump for Postgres "12.9" at "/Applications/Postgres.app/Contents/Versions/12/bin/pg_dump"
09:35:21 3926 INFO   /Applications/Postgres.app/Contents/Versions/12/bin/pg_dump -Fc --section pre-data --file /tmp/target/schema/pre.dump 'port=5501 dbname=demo'
09:35:22 3926 INFO   /Applications/Postgres.app/Contents/Versions/12/bin/pg_dump -Fc --section post-data --file /tmp/target/schema/post.dump 'port=5501 dbname=demo'


Once the previous command is finished, the pg_dump output files can be found in /tmp/target/schema and are named pre.dump and post.dump. Other files and directories have been created.

$ find /tmp/target
/tmp/target
/tmp/target/pgcopydb.pid
/tmp/target/schema
/tmp/target/schema/post.dump
/tmp/target/schema/pre.dump
/tmp/target/run
/tmp/target/run/tables
/tmp/target/run/indexes


Then we have almost the same thing when using the other forms.

We can see that pgcopydb dump pre-data only does the pre-data section of the dump.

$ pgcopydb dump pre-data --source "port=5501 dbname=demo" --target /tmp/target
09:35:21 3926 INFO  Dumping database from "port=5501 dbname=demo"
09:35:21 3926 INFO  Dumping database into directory "/tmp/target"
09:35:21 3926 INFO  Found a stale pidfile at "/tmp/target/pgcopydb.pid"
09:35:21 3926 WARN  Removing the stale pid file "/tmp/target/pgcopydb.pid"
09:35:21 3926 INFO  Using pg_dump for Postgres "12.9" at "/Applications/Postgres.app/Contents/Versions/12/bin/pg_dump"
09:35:21 3926 INFO   /Applications/Postgres.app/Contents/Versions/12/bin/pg_dump -Fc --section pre-data --file /tmp/target/schema/pre.dump 'port=5501 dbname=demo'


And then pgcopydb dump post-data only does the post-data section of the dump.

$ pgcopydb dump post-data --source "port=5501 dbname=demo" --target /tmp/target
09:35:21 3926 INFO  Dumping database from "port=5501 dbname=demo"
09:35:21 3926 INFO  Dumping database into directory "/tmp/target"
09:35:21 3926 INFO  Found a stale pidfile at "/tmp/target/pgcopydb.pid"
09:35:21 3926 WARN  Removing the stale pid file "/tmp/target/pgcopydb.pid"
09:35:21 3926 INFO  Using pg_dump for Postgres "12.9" at "/Applications/Postgres.app/Contents/Versions/12/bin/pg_dump"
09:35:21 3926 INFO   /Applications/Postgres.app/Contents/Versions/12/bin/pg_dump -Fc --section post-data --file /tmp/target/schema/post.dump 'port=5501 dbname=demo'


Dimitri Fontaine

2022, Dimitri Fontaine

November 3, 2022 0.10