pgcopydb

pgcopydb - copy an entire Postgres database from source to target

Synopsis

pgcopydb provides the following commands:

pgcopydb
  clone     Clone an entire database from source to target
  fork      Clone an entire database from source to target
  follow    Replay changes from the source database to the target database
  snapshot  Create and export a snapshot on the source database
+ copy      Implement the data section of the database copy
+ dump      Dump database objects from a Postgres instance
+ restore   Restore database objects into a Postgres instance
+ list      List database objects from a Postgres instance
+ stream    Stream changes from the source database
  help      Print help message
  version   Print pgcopydb version

Description

The pgcopydb command implements a full migration of an entire Postgres database from a source instance to a target instance. Both the Postgres instances must be available for the entire duration of the command.

The pgcopydb command also implements a full Logical Decoding client for Postgres, allowing Change Data Capture to replay data changes (DML) happening on the source database after the base copy snapshot. The pgcopydb logical decoding client code is compatible with both test_decoding and wal2json output plugins, and defaults to using test_decoding.

pgcopydb help

The pgcopydb help command lists all the supported sub-commands:

$ pgcopydb help
 pgcopydb
   clone     Clone an entire database from source to target
   fork      Clone an entire database from source to target
   follow    Replay changes from the source database to the target database
   copy-db   Clone an entire database from source to target
   snapshot  Create and export a snapshot on the source database
 + copy      Implement the data section of the database copy
 + dump      Dump database objects from a Postgres instance
 + restore   Restore database objects into a Postgres instance
 + list      List database objects from a Postgres instance
 + stream    Stream changes from the source database
   ping      Attempt to connect to the source and target instances
   help      Print help message
   version   Print pgcopydb version

 pgcopydb copy
   db           Copy an entire database from source to target
   roles        Copy the roles from the source instance to the target instance
   extensions   Copy the extensions from the source instance to the target instance
   schema       Copy the database schema from source to target
   data         Copy the data section from source to target
   table-data   Copy the data from all tables in database from source to target
   blobs        Copy the blob data from the source database to the target
   sequences    Copy the current value from all sequences in database from source to target
   indexes      Create all the indexes found in the source database in the target
   constraints  Create all the constraints found in the source database in the target

 pgcopydb dump
   schema     Dump source database schema as custom files in work directory
   pre-data   Dump source database pre-data schema as custom files in work directory
   post-data  Dump source database post-data schema as custom files in work directory
   roles      Dump source database roles as custome file in work directory

 pgcopydb restore
   schema      Restore a database schema from custom files to target database
   pre-data    Restore a database pre-data schema from custom file to target database
   post-data   Restore a database post-data schema from custom file to target database
   roles       Restore database roles from SQL file to target database
   parse-list  Parse pg_restore --list output from custom file

 pgcopydb list
   databases    List databases
   extensions   List all the source extensions to copy
   collations   List all the source collations to copy
   tables       List all the source tables to copy data from
   table-parts  List a source table copy partitions
   sequences    List all the source sequences to copy data from
   indexes      List all the indexes to create again after copying the data
   depends      List all the dependencies to filter-out
   schema       List the schema to migrate, formatted in JSON
   progress     List the progress

 pgcopydb stream
   setup      Setup source and target systems for logical decoding
   cleanup    Cleanup source and target systems for logical decoding
   prefetch   Stream JSON changes from the source database and transform them to SQL
   catchup    Apply prefetched changes from SQL files to the target database
   replay     Replay changes from the source to the target database, live
 + sentinel   Maintain a sentinel table on the source database
   receive    Stream changes from the source database
   transform  Transform changes from the source database into SQL commands
   apply      Apply changes from the source database into the target database

 pgcopydb stream sentinel
   create  Create the sentinel table on the source database
   drop    Drop the sentinel table on the source database
   get     Get the sentinel table values on the source database
 + set     Maintain a sentinel table on the source database

 pgcopydb stream sentinel set
   startpos  Set the sentinel start position LSN on the source database
   endpos    Set the sentinel end position LSN on the source database
   apply     Set the sentinel apply mode on the source database
   prefetch  Set the sentinel prefetch mode on the source database

pgcopydb version

The pgcopydb version command outputs the version string of the version of pgcopydb used, and can do that in the JSON format when using the --json option.

$ pgcopydb version
pgcopydb version 0.13.1.g868ad77
compiled with PostgreSQL 13.11 (Debian 13.11-0+deb11u1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
compatible with Postgres 10, 11, 12, 13, 14, and 15

In JSON:

$ pgcopydb version --json
{
    "pgcopydb": "0.13.1.g868ad77",
    "pg_major": "13",
    "pg_version": "13.11 (Debian 13.11-0+deb11u1)",
    "pg_version_str": "PostgreSQL 13.11 (Debian 13.11-0+deb11u1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit",
    "pg_version_num": 130011
}

The details about the Postgres version applies to the version that’s been used to build pgcopydb from sources, so that’s the version of the client library libpq really.

pgcopydb ping

The pgcopydb ping command attempts to connect to both the source and the target Postgres databases, concurrently.

pgcopydb ping: Attempt to connect to the source and target instances
usage: pgcopydb ping  --source ... --target ...

  --source              Postgres URI to the source database
  --target              Postgres URI to the target database

An example output looks like the following:

$ pgcopydb ping
18:04:48 84679 INFO   Running pgcopydb version 0.10.31.g7e5fbb8.dirty from "/Users/dim/dev/PostgreSQL/pgcopydb/src/bin/pgcopydb/pgcopydb"
18:04:48 84683 INFO   Successfully could connect to target database at "postgres://@:/plop?"
18:04:48 84682 INFO   Successfully could connect to source database at "postgres://@:/pagila?"

This command implements a retry policy (named Decorrelated Jitter) and can be used in automation to make sure that the databases are ready to accept connections.