.. _pgcopydb_copy: pgcopydb copy ============= pgcopydb copy - Implement the data section of the database copy This command prefixes the following sub-commands: .. include:: ../include/copy.rst Those commands implement a part of the whole database copy operation as detailed in section :ref:`pgcopydb_clone`. Only use those commands to debug a specific part, or because you know that you just want to implement that step. .. warning:: Using the ``pgcopydb clone`` command is strongly advised. This mode of operations is useful for debugging and advanced use cases only. .. _pgcopydb_copy_db: pgcopydb copy db ---------------- pgcopydb copy db - Copy an entire database from source to target The command ``pgcopydb copy db`` is an alias for ``pgcopydb clone``. See also :ref:`pgcopydb_clone`. .. include:: ../include/copy-db.rst .. _pgcopydb_copy_roles: pgcopydb copy roles ------------------- pgcopydb copy roles - Copy the roles from the source instance to the target instance The command ``pgcopydb copy roles`` implements both :ref:`pgcopydb_dump_roles` and then :ref:`pgcopydb_restore_roles`. .. include:: ../include/copy-roles.rst .. note:: In Postgres, roles are a global object. This means roles do not belong to any specific database, and as a result, even when the ``pgcopydb`` tool otherwise works only in the context of a specific database, this command is not limited to roles that are used within a single database. When a role already exists on the target database, its restoring is entirely skipped, which includes skipping both the ``CREATE ROLE`` and the ``ALTER ROLE`` commands produced by ``pg_dumpall --roles-only``. 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. .. _pgcopydb_copy_extensions: pgcopydb copy extensions ------------------------ pgcopydb copy extensions - Copy the extensions from the source instance to the target instance The command ``pgcopydb copy extensions`` gets a list of the extensions installed on the source database, and for each of them run the SQL command CREATE EXTENSION IF NOT EXISTS. .. include:: ../include/copy-extensions.rst When copying extensions, this command also takes care of copying any `Extension Configuration Tables`__ user-data to the target database. __ https://www.postgresql.org/docs/current/extend-extensions.html#EXTEND-EXTENSIONS-CONFIG-TABLES .. _pgcopydb_copy_schema: pgcopydb copy schema -------------------- pgcopydb copy schema - Copy the database schema from source to target The command ``pgcopydb copy schema`` implements the schema only section of the clone steps. .. include:: ../include/copy-schema.rst .. _pgcopydb_copy_data: pgcopydb copy data ------------------ pgcopydb copy data - Copy the data section from source to target The command ``pgcopydb copy data`` implements the data section of the clone steps. .. include:: ../include/copy-data.rst .. note:: The current command line has both the commands ``pgcopydb copy table-data`` and ``pgcopydb copy data``, which are looking quite similar but implement different steps. Be careful for now. This will change later. The ``pgcopydb copy data`` command implements the following steps:: $ pgcopydb copy table-data $ pgcopydb copy blobs $ pgcopydb copy indexes $ pgcopydb copy constraints $ pgcopydb copy sequences $ vacuumdb -z Those steps are actually done concurrently to one another when that's possible, in the same way as the main command ``pgcopydb clone`` would. The only difference is that the ``pgcopydb clone`` command also prepares and finishes the schema parts of the operations (pre-data, then post-data), which the ``pgcopydb copy data`` command ignores. .. _pgcopydb_copy_table_data: pgcopydb copy table-data ------------------------ pgcopydb copy table-data - Copy the data from all tables in database from source to target The command ``pgcopydb copy table-data`` fetches the list of tables from the source database and runs a COPY TO command on the source database and sends the result to the target database using a COPY FROM command directly, avoiding disks entirely. .. include:: ../include/copy-table-data.rst .. _pgcopydb_copy_blobs: pgcopydb copy blobs ------------------- pgcopydb copy blobs - Copy the blob data from the source database to the target The command ``pgcopydb copy blobs`` fetches list of large objects (aka blobs) from the source database and copies their data parts to the target database. By default the command assumes that the large objects metadata have already been taken care of, because of the behaviour of ``pg_dump --section=pre-data``. .. include:: ../include/copy-blobs.rst .. _pgcopydb_copy_sequences: pgcopydb copy sequences ----------------------- pgcopydb copy sequences - Copy the current value from all sequences in database from source to target The command ``pgcopydb copy sequences`` fetches the list of sequences from the source database, then for each sequence fetches the ``last_value`` and ``is_called`` properties the same way pg_dump would on the source database, and then for each sequence call ``pg_catalog.setval()`` on the target database. .. include:: ../include/copy-sequences.rst .. _pgcopydb_copy_indexes: pgcopydb copy indexes --------------------- pgcopydb copy indexes - Create all the indexes found in the source database in the target The command ``pgcopydb copy indexes`` fetches the list of indexes from the source database and runs each index CREATE INDEX statement on the target database. The statements for the index definitions are modified to include IF NOT EXISTS and allow for skipping indexes that already exist on the target database. .. include:: ../include/copy-indexes.rst .. _pgcopydb_copy_constraints: pgcopydb copy constraints ------------------------- pgcopydb copy constraints - Create all the constraints found in the source database in the target The command ``pgcopydb copy constraints`` fetches the list of indexes from the source database and runs each index ALTER TABLE ... ADD CONSTRAINT ... USING INDEX statement on the target database. The indexes must already exist, and the command will fail if any constraint is found existing already on the target database. .. include:: ../include/copy-constraints.rst Description ----------- These commands allow implementing a specific step of the pgcopydb operations at a time. It's useful mainly for debugging purposes, though some advanced and creative usage can be made from the commands. The target schema is not created, so it needs to have been taken care of first. It is possible to use the commands :ref:`pgcopydb_dump_schema` and then :ref:`pgcopydb_restore_pre_data` to prepare your target database. To implement the same operations as a ``pgcopydb clone`` command would, use the following recipe: :: $ export PGCOPYDB_SOURCE_PGURI="postgres://user@source/dbname" $ export PGCOPYDB_TARGET_PGURI="postgres://user@target/dbname" $ pgcopydb dump schema $ pgcopydb restore pre-data --resume --not-consistent $ pgcopydb copy table-data --resume --not-consistent $ pgcopydb copy sequences --resume --not-consistent $ pgcopydb copy indexes --resume --not-consistent $ pgcopydb copy constraints --resume --not-consistent $ vacuumdb -z $ pgcopydb restore post-data --resume --not-consistent The main ``pgcopydb clone`` is still better at concurrency than doing those steps manually, as it will create the indexes for any given table as soon as the table-data section is finished, without having to wait until the last table-data has been copied over. Same applies to constraints, and then vacuum analyze. Options ------- The following options are available to ``pgcopydb copy`` sub-commands: --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 --target Connection string to the target Postgres instance. --dir During its normal operations pgcopydb creates a lot of temporary files to track sub-processes progress. Temporary files are created in the directory specified by this option, or defaults to ``${TMPDIR}/pgcopydb`` when the environment variable is set, or otherwise to ``/tmp/pgcopydb``. --no-role-passwords Do not dump passwords for roles. When restored, roles will have a null password, and password authentication will always fail until the password is set. Since password values aren't needed when this option is specified, the role information is read from the catalog view pg_roles instead of pg_authid. Therefore, this option also helps if access to pg_authid is restricted by some security policy. --table-jobs How many tables can be processed in parallel. This limit only applies to the COPY operations, more sub-processes will be running at the same time that this limit while the CREATE INDEX operations are in progress, though then the processes are only waiting for the target Postgres instance to do all the work. --index-jobs How many indexes can be built in parallel, globally. A good option is to set this option to the count of CPU cores that are available on the Postgres target system, minus some cores that are going to be used for handling the COPY operations. --large-object-jobs How many worker processes to start to copy Large Objects concurrently. --split-tables-larger-than Allow :ref:`same_table_concurrency` when processing the source database. This environment variable value is expected to be a byte size, and bytes units B, kB, MB, GB, TB, PB, and EB are known. --skip-large-objects Skip copying large objects, also known as blobs, when copying the data from the source database to the target database. --restart When running the pgcopydb command again, if the work directory already contains information from a previous run, then the command refuses to proceed and delete information that might be used for diagnostics and forensics. In that case, the ``--restart`` option can be used to allow pgcopydb to delete traces from a previous run. --resume When the pgcopydb command was terminated before completion, either by an interrupt signal (such as C-c or SIGTERM) or because it crashed, it is possible to resume the database migration. When resuming activity from a previous run, table data that was fully copied over to the target server is not sent again. Table data that was interrupted during the COPY has to be started from scratch even when using ``--resume``: the COPY command in Postgres is transactional and was rolled back. Same reasonning applies to the CREATE INDEX commands and ALTER TABLE commands that pgcopydb issues, those commands are skipped on a ``--resume`` run only if known to have run through to completion on the previous one. Finally, using ``--resume`` requires the use of ``--not-consistent``. --not-consistent In order to be consistent, pgcopydb exports a Postgres snapshot by calling the `pg_export_snapshot()`__ function on the source database server. The snapshot is then re-used in all the connections to the source database server by using the ``SET TRANSACTION SNAPSHOT`` command. Per the Postgres documentation about ``pg_export_snapshot``: Saves the transaction's current snapshot and returns a text string identifying the snapshot. This string must be passed (outside the database) to clients that want to import the snapshot. The snapshot is available for import only until the end of the transaction that exported it. __ https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-SNAPSHOT-SYNCHRONIZATION-TABLE Now, when the pgcopydb process was interrupted (or crashed) on a previous run, it is possible to resume operations, but the snapshot that was exported does not exists anymore. The pgcopydb command can only resume operations with a new snapshot, and thus can not ensure consistency of the whole data set, because each run is now using their own snapshot. --snapshot 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. --use-copy-binary Use the COPY WITH (FORMAT BINARY) instead of the COPY command. See also documentation for `COPY`__. __ https://www.postgresql.org/docs/current/sql-copy.html --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. PGCOPYDB_TARGET_PGURI Connection string to the target Postgres instance. When ``--target`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_TABLE_JOBS Number of concurrent jobs allowed to run COPY operations in parallel. When ``--table-jobs`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_INDEX_JOBS Number of concurrent jobs allowed to run CREATE INDEX operations in parallel. When ``--index-jobs`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_RESTORE_JOBS Number of concurrent jobs allowed to run `pg_restore` operations in parallel. When ``--restore-jobs`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_LARGE_OBJECTS_JOBS Number of concurrent jobs allowed to copy Large Objects data in parallel. When ``--large-objects-jobs`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_SPLIT_TABLES_LARGER_THAN Allow :ref:`same_table_concurrency` when processing the source database. This environment variable value is expected to be a byte size, and bytes units B, kB, MB, GB, TB, PB, and EB are known. When ``--split-tables-larger-than`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_SPLIT_MAX_PARTS Limit the maximum number of parts when :ref:`same_table_concurrency` is used. When ``--split-max-parts`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_ESTIMATE_TABLE_SIZES When true (or *yes*, or *on*, or 1, same input as a Postgres boolean) then pgcopydb estimates the size of tables to determine whether or not to split tables. This option is only useful when querying the relation sizes on source database is costly. When ``--estimate-table-sizes`` is ommitted from the command line, then this environment variable is used. PGCOPYDB_DROP_IF_EXISTS When true (or *yes*, or *on*, or 1, same input as a Postgres boolean) then pgcopydb uses the pg_restore options ``--clean --if-exists`` when creating the schema on the target Postgres instance. PGCOPYDB_SNAPSHOT Postgres snapshot identifier to re-use, see also ``--snapshot``. PGCOPYDB_USE_COPY_BINARY When true (or *yes*, or *on*, or 1, same input as a Postgres boolean) then pgcopydb uses the COPY WITH (FORMAT BINARY) instead of the COPY command, same as when using the ``--use-copy-binary`` option. TMPDIR The pgcopydb command creates all its work files and directories in ``${TMPDIR}/pgcopydb``, and defaults to ``/tmp/pgcopydb``. Examples -------- Let's export the Postgres databases connection strings to make it easy to re-use them all along: :: $ export PGCOPYDB_SOURCE_PGURI=postgres://pagila:0wn3d@source/pagila $ export PGCOPYDB_TARGET_PGURI=postgres://pagila:0wn3d@target/pagila Now, first dump the schema: :: $ pgcopydb dump schema 08:27:48.633 44371 INFO Using work dir "/tmp/pgcopydb" 08:27:48.634 44371 INFO Dumping database from "postgres://pagila:0wn3d@source/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 08:27:48.634 44371 INFO Dumping database into directory "/tmp/pgcopydb" 08:27:48.634 44371 INFO Using pg_dump for Postgres "16.2" at "/usr/bin/pg_dump" 08:27:48.971 44371 INFO Fetched information for 5 tables (including 0 tables split in 0 partitions total), with an estimated total of 1000 thousands tuples and 128 MB on-disk 08:27:48.978 44371 INFO Fetched information for 4 indexes (supporting 4 constraints) 08:27:48.983 44371 INFO Fetching information for 1 sequences 08:27:48.996 44371 INFO Fetched information for 1 extensions 08:27:49.072 44371 INFO Found 5 indexes (supporting 5 constraints) in the target database 08:27:49.078 44371 INFO /usr/bin/pg_dump -Fc --section=pre-data --section=post-data --file /tmp/pgcopydb/schema/schema.dump 'postgres://pagila:0wn3d@source/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60' Now restore the pre-data schema on the target database, cleaning up the already existing objects if any, which allows running this test scenario again and again. It might not be what you want to do in your production target instance though! :: $ PGCOPYDB_DROP_IF_EXISTS=on pgcopydb restore pre-data --no-owner --resume --not-consistent 08:30:13.621 44597 INFO Using work dir "/tmp/pgcopydb" 08:30:13.621 44597 INFO Restoring database from existing files at "/tmp/pgcopydb" 08:30:13.706 44597 INFO Found 5 indexes (supporting 5 constraints) in the target database 08:30:13.710 44597 INFO Using pg_restore for Postgres "16.2" at "/usr/bin/pg_restore" 08:30:13.711 44597 INFO [TARGET] Restoring database into "postgres://pagila:0wn3d@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 08:30:13.730 44597 INFO Drop tables on the target database, per --drop-if-exists 08:30:13.774 44597 INFO /usr/bin/pg_restore --dbname 'postgres://pagila:0wn3d@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60' --section pre-data --jobs 4 --clean --if-exists --no-owner --use-list /tmp/pgcopydb/schema/pre-filtered.list /tmp/pgcopydb/schema/schema.dump Then copy the data over: :: $ pgcopydb copy table-data --resume --not-consistent 08:34:02.813 44834 INFO [SOURCE] Copying database from "postgres://pagila:0wn3d@source/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 08:34:02.813 44834 INFO [TARGET] Copying database into "postgres://pagila:0wn3d@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 08:34:02.861 44834 INFO Using work dir "/tmp/pgcopydb" 08:34:02.862 44834 INFO Copy data from source to target in sub-processes 08:34:02.863 44834 INFO Re-using catalog caches 08:34:02.863 44834 INFO STEP 4: starting 4 table-data COPY processes And now create the indexes on the target database, using the index definitions from the source database: :: $ pgcopydb copy indexes --resume --not-consistent 14:28:53 47 INFO Running pgcopydb version 0.13.38.g22e6544.dirty from "/usr/local/bin/pgcopydb" 14:28:53 47 INFO [SOURCE] Copying database from "postgres://pagila@source/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 14:28:53 47 INFO [TARGET] Copying database into "postgres://pagila@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 14:28:53 47 INFO Schema dump for pre-data and post-data section have been done 14:28:53 47 INFO Pre-data schema has been restored on the target instance 14:28:53 47 INFO All the table data has been copied to the target instance 14:28:53 47 INFO All the indexes have been copied to the target instance 14:28:53 47 INFO Fetched information for 54 indexes 14:28:53 47 INFO Creating 54 indexes in the target database using 4 processes Step Connection Duration Transfer Concurrency -------------------------------------------------- ---------- ---------- ---------- ------------ Dump Schema source 0ms 1 Catalog Queries (table ordering, filtering, etc) source 0ms 1 Prepare Schema target 0ms 1 COPY, INDEX, CONSTRAINTS, VACUUM (wall clock) both 0ms 4 + 8 COPY (cumulative) both 0ms 0 B 4 Large Objects (cumulative) both 4 CREATE INDEX, CONSTRAINTS (cumulative) target 0ms 4 Finalize Schema target 0ms 1 -------------------------------------------------- ---------- ---------- ---------- ------------ Total Wall Clock Duration both 696ms 4 + 8 -------------------------------------------------- ---------- ---------- ---------- ------------ Now re-create the constraints (primary key, unique constraints) from the source database schema into the target database: :: $ pgcopydb copy constraints --resume --not-consistent 14:28:54 53 INFO Running pgcopydb version 0.13.38.g22e6544.dirty from "/usr/local/bin/pgcopydb" 14:28:54 53 INFO [SOURCE] Copying database from "postgres://pagila@source/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 14:28:54 53 INFO [TARGET] Copying database into "postgres://pagila@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 14:28:54 53 INFO Schema dump for pre-data and post-data section have been done 14:28:54 53 INFO Pre-data schema has been restored on the target instance 14:28:54 53 INFO All the table data has been copied to the target instance 14:28:54 53 INFO All the indexes have been copied to the target instance 14:28:54 53 INFO Create constraints 14:28:54 53 INFO Fetched information for 54 indexes 14:28:54 53 INFO Creating 54 indexes in the target database using 4 processes Step Connection Duration Transfer Concurrency -------------------------------------------------- ---------- ---------- ---------- ------------ Dump Schema source 0ms 1 Catalog Queries (table ordering, filtering, etc) source 0ms 1 Prepare Schema target 0ms 1 COPY, INDEX, CONSTRAINTS, VACUUM (wall clock) both 0ms 4 + 8 COPY (cumulative) both 0ms 0 B 4 Large Objects (cumulative) both 4 CREATE INDEX, CONSTRAINTS (cumulative) target 0ms 4 Finalize Schema target 0ms 1 -------------------------------------------------- ---------- ---------- ---------- ------------ Total Wall Clock Duration both 283ms 4 + 8 -------------------------------------------------- ---------- ---------- ---------- ------------ The next step is a VACUUM ANALYZE on each table that's been just filled-in with the data, and for that we can just use the `vacuumdb`__ command from Postgres: __ https://www.postgresql.org/docs/current/app-vacuumdb.html :: $ vacuumdb --analyze --dbname "$PGCOPYDB_TARGET_PGURI" --jobs 4 vacuumdb: vacuuming database "pagila" Finally we can restore the post-data section of the schema: :: $ pgcopydb restore post-data --resume --not-consistent 14:28:54 60 INFO Running pgcopydb version 0.13.38.g22e6544.dirty from "/usr/local/bin/pgcopydb" 14:28:54 60 INFO Schema dump for pre-data and post-data section have been done 14:28:54 60 INFO Pre-data schema has been restored on the target instance 14:28:54 60 INFO All the table data has been copied to the target instance 14:28:54 60 INFO All the indexes have been copied to the target instance 14:28:54 60 INFO Restoring database from existing files at "/tmp/pgcopydb" 14:28:54 60 INFO Using pg_restore for Postgres "16.1" at "/usr/bin/pg_restore" 14:28:54 60 INFO [TARGET] Restoring database into "postgres://pagila@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60" 14:28:55 60 INFO /usr/bin/pg_restore --dbname 'postgres://pagila@target/pagila?keepalives=1&keepalives_idle=10&keepalives_interval=10&keepalives_count=60' --single-transaction --use-list /tmp/pgcopydb/schema/post-filtered.list /tmp/pgcopydb/schema/schema.dump