Extracts a database into a single script file or other archive file.
pg_dump [<connection_options>] [<dump_options>] <dbname> pg_dump --help pg_dump --version
<connection_options> = [-h <host> | --host <host>] [-p <port> | -- port <port>] [-U <username> | --username <username>] [-W | --password] <dump_options> = [-a | --data-only] [-b | --blobs] [-c | --clean] [-C | --create] [-d | --inserts] [(-D | --column-inserts) ] [-E <encoding> | --encoding <encoding>] [-f <file> | --file <file>] [-F(p|t|c)] | --format (plain|custom|tar)] [-i | --ignore-version] [-n <schema> | --schema <schema>] [-N <schema> | --exclude-schema <schema>] [-o | --oids] [-O | --no-owner] [-s | --schema-only] [-S <username> | --superuser <username>] [-t <table> | --table <table>] [-T <table> | --exclude-table <table>] [-v | --verbose] [(-x | --no-privileges) ] [--disable-dollar-quoting] [--disable-triggers] [--use-set-session-authorization] [--gp-syntax | --no-gp-syntax] [-Z <0..9> | --compress <0..9>]
pg_dump is a standard PostgreSQL utility for backing up a database, and is also supported in HAWQ. It creates a single (non-parallel) dump file.
pg_dump if you are migrating your data to another database vendor’s system, or to another HAWQ system with a different segment configuration (for example, if the system you are migrating to has greater or fewer segment instances). To restore, you must use the corresponding pg_restore utility (if the dump file is in archive format), or you can use a client program such as psql (if the dump file is in plain text format).
pg_dump is compatible with regular PostgreSQL, it can be used to migrate data into HAWQ. The
pg_dump utility in HAWQ is very similar to the PostgreSQL
pg_dump utility, with the following exceptions and limitations:
- If using
pg_dumpto backup a HAWQ database, keep in mind that the dump operation can take a long time (several hours) for very large databases. Also, you must make sure you have sufficient disk space to create the dump file.
- If you are migrating data from one HAWQ system to another, use the
--gp-syntaxcommand-line option to include the
DISTRIBUTED BYclause in
CREATE TABLEstatements. This ensures that HAWQ table data is distributed with the correct distribution key columns upon restore.
pg_dump makes consistent backups even if the database is being used concurrently.
pg_dump does not block other users accessing the database (readers or writers).
When used with one of the archive file formats and combined with
pg_dump provides a flexible archival and transfer mechanism.
pg_dump can be used to backup an entire database, then
pg_restorecan be used to examine the archive and/or select which parts of the database are to be restored. The most flexible output file format is the custom format (
-Fc). It allows for selection and reordering of all archived items, and is compressed by default. The tar format (
-Ft) is not compressed and it is not possible to reorder data when loading, but it is otherwise quite flexible. It can be manipulated with standard UNIX tools such as
PGDATABASEis used. If that is not set, the user name specified for the connection is used.
--schema-onlyis specified, so the
-bswitch is only useful to add large objects to selective dumps.
DROPcommands are added to the DDL dump output files so that when you use those files to do a restore, the
DROPcommands are run prior to the
CREATEcommands. This option is only meaningful for the plain-text format. For the archive formats, you may specify the option when you call pg_restore.
INSERTcommands (rather than
COPY). This will make restoration very slow; it is mainly useful for making dumps that can be loaded into non-PostgreSQL-based databases. Also, since this option generates a separate command for each row, an error in reloading a row causes only that row to be lost rather than the entire table contents. Note that the restore may fail altogether if you have rearranged column order. The
-Doption is safe against column order changes, though even slower.
INSERTcommands with explicit column names
, ...) VALUES ...). This will make restoration very slow; it is mainly useful for making dumps that can be loaded into non-PostgreSQL-based databases. Also, since this option generates a separate command for each row, an error in reloading a row causes only that row to be lost rather than the entire table contents.
PGCLIENTENCODINGenvironment variable to the desired dump encoding.)
p, plain — Output a plain-text SQL script file (the default).
c, custom — Output a custom archive suitable for input into pg_restore. This is the most flexible format in that it allows reordering of loading data as well as object definitions. This format is also compressed by default.
t, tar — Output a tar archive suitable for input into pg_restore. Using this archive format allows reordering and/or exclusion of database objects at the time the database is restored. It is also possible to limit which data is reloaded at restore time.
pg_dumpand the database server.
pg_dumpcan dump from servers running previous releases of HAWQ (or PostgreSQL). However, some older versions might not be supported. Use this option if you need to override the version check.
-nswitches. Also, the schema parameter is interpreted as a pattern according to the same rules used by
\dcommands, so multiple schemas can also be selected by writing wildcard characters in the pattern. When using wildcards, be careful to quote the pattern if needed to prevent the shell from expanding the wildcards.
-n is specified,
pg_dump makes no attempt to dump any other database objects that the selected schema(s) may depend upon. Therefore, there is no guarantee that the results of a specific-schema dump can be successfully restored by themselves into a clean database.
Note: Non-schema objects such as blobs are not dumped when
-n is specified. You can add blobs back to the dump with the
-Ncan be specified multiple times to exclude schemas that match several different patterns. When both
-Nare specified, the behavior is to dump only schemas that match at least one
-nswitch but no
-n, then schemas matching
-Nare excluded from an otherwise normal dump.
SET SESSION AUTHORIZATIONstatements to set ownership of created database objects. These statements will fail when the script is run unless it is started by a superuser (or the same user that owns all of the objects in the script). To make a script that can be restored by any user, but will give that user ownership of all the objects, specify
-O. This option is only meaningful for the plain-text format. For the archive formats, you may specify the option when you call pg_restore.
--disable-triggersis used. It is better to leave this out, and instead start the resulting script as a superuser.
Note: HAWQ does not support user-defined triggers.
Multiple tables can be selected by writing multiple
-t switches. Also, the table parameter is interpreted as a pattern according to the same rules used by
\d commands, so multiple tables can also be selected by writing wildcard characters in the pattern. When using wildcards, be careful to quote the pattern if needed to prevent the shell from expanding the wildcards. The
-N switches have no effect when
-t is used, because tables selected by
-t will be dumped regardless of those switches, and non-table objects will not be dumped.
-t is specified,
pg_dump makes no attempt to dump any other database objects that the selected table(s) may depend upon. Therefore, there is no guarantee that the results of a specific-table dump can be successfully restored by themselves into a clean database.
-t cannot be used to specify a child table partition. To dump a partitioned table, you must specify the parent table name.
-Tcan be given more than once to exclude tables matching any of several patterns. When both
-Tare given, the behavior is to dump just the tables that match at least one
-tswitch but no
-t, then tables matching
-Tare excluded from what is otherwise a normal dump.
pg_dumpto output detailed object comments and start/stop times to the dump file, and progress messages to standard error.
pg_dumpto include commands to temporarily disable triggers on the target tables while the data is reloaded. Use this if you have triggers on the tables that you do not want to invoke during data reload. The commands emitted for
--disable-triggersmust be done as superuser. So, you should also specify a superuser name with
-S, or preferably be careful to start the resulting script as a superuser. This option is only meaningful for the plain-text format. For the archive formats, you may specify the option when you call pg_restore.
Note: HAWQ does not support user-defined triggers.
SET SESSION AUTHORIZATIONcommands instead of
ALTER OWNERcommands to determine object ownership. This makes the dump more standards compatible, but depending on the history of the objects in the dump, may not restore properly. A dump using
SET SESSION AUTHORIZATIONwill require superuser privileges to restore correctly, whereas
ALTER OWNERrequires lesser privileges.
--gp-syntaxto dump HAWQ syntax in the
CREATE TABLEstatements. This allows the distribution policy (
DISTRIBUTED RANDOMLYclauses) of a HAWQ table to be dumped, which is useful for restoring into other HAWQ systems. The default is to include HAWQ syntax when connected to a HAWQ system, and to exclude it when connected to a regular PostgreSQL system.
PGHOSTor defaults to localhost.
PGPORTor defaults to 5432.
PGUSERor defaults to the current system role name.
When a data-only dump is chosen and the option
--disable-triggers is used,
pg_dump emits commands to disable triggers on user tables before inserting the data and commands to re-enable them after the data has been inserted. If the restore is stopped in the middle, the system catalogs may be left in the wrong state.
tar archives are limited to a size less than 8 GB. (This is an inherent limitation of the
tar file format.) Therefore this format cannot be used if the textual representation of any one table exceeds that size. The total size of a tar archive and any of the other output formats is not limited, except possibly by the operating system.
The dump file produced by
pg_dump does not contain the statistics used by the optimizer to make query planning decisions. Therefore, it is wise to run
ANALYZE after restoring from a dump file to ensure good performance.
Dump a database called
mydb into a SQL-script file:
$ pg_dump mydb > db.sql
To reload such a script into a (freshly created) database named
$ psql -d newdb -f db.sql
Dump a HAWQ in tar file format and include distribution policy information:
$ pg_dump -Ft --gp-syntax mydb > db.tar
To dump a database into a custom-format archive file:
$ pg_dump -Fc mydb > db.dump
To reload an archive file into a (freshly created) database named
$ pg_restore -d newdb db.dump
Note: A warning related to the
gp_enable_column_oriented_table parameter may appear. If it does, disregard it.
To dump a single table named
$ pg_dump -t mytab mydb > db.sql
To specify an upper-case or mixed-case name in
-t and related switches, you need to double-quote the name; else it will be folded to lower case. But double quotes are special to the shell, so in turn they must be quoted. Thus, to dump a single table with a mixed-case name, you need something like:
$ pg_dump -t '"MixedCaseName"' mydb > mytab.sql