pg_dump

pg_dump — 將 PostgreSQL 資料庫匯出到腳本檔案或其他封存檔案中

語法

pg_dump [connection-option...] [option...] [dbname]

說明

pg_dump 是用於備份 PostgreSQL 資料庫的工具程式。即使同時也在使用資料庫，它會進行具有一致性的備份。pg_dump 不會阻礙其他使用者存取資料庫（讀取或寫入皆不會阻礙）。

pg_dump 只匯出一個數據庫。要備份整個叢集，或備份叢集中所有資料庫共有的全域物件（例如角色和資料表空間），請使用 pg_dumpall。

Dump 可以是腳本或封存檔案格式輸出。腳本匯出是純文字檔案，其中包含將資料庫重建到保存時所處狀態所需的 SQL 命令。要從此類腳本還原，請將其腳本檔案提供給 psql。腳本檔案甚至可以在其他機器和其他系統結構上用於重建資料庫；進行一些修改，甚至在其他 SQL 資料庫產品上還原。

另一種封存檔案格式必須與 pg_restore 一起使用才能重建資料庫。它們允許 pg_restore 對還原哪些東西有選擇性，甚至可以在還原之前對資料進行重新排序。封存檔案格式設計為可跨系統結構移植。

When used with one of the archive file formats and combined with pg_restore, pg_dump provides a flexible archival and transfer mechanism. pg_dump can be used to backup an entire database, then pg_restore can be used to examine the archive and/or select which parts of the database are to be restored. The most flexible output file formats are the “custom” format (-Fc) and the “directory”format (-Fd). They allow for selection and reordering of all archived items, support parallel restoration, and are compressed by default. The “directory” format is the only format that supports parallel dumps.

While running pg_dump, one should examine the output for any warnings (printed on standard error), especially in light of the limitations listed below.

選項

以下命令列選項來控制輸出的內容和格式。

dbname

指定要匯出的資料庫的名稱。如果未指定，則使用環境變數 PGDATABASE。如果環境變數也未設定，則使用連線的使用者名稱作為資料庫名稱。

-a --data-only

僅匯出資料，而不匯出結構（資料結構定義）。資料表的資料內容、大型物件和序列值將被匯出。

此選項與 --section = data 相似，但由於歷史原因並不完全相同。

-b --blobs

Include large objects in the dump. This is the default behavior except when --schema, --table, or --schema-only is specified. The -b switch is therefore only useful to add large objects to dumps where a specific schema or table has been requested. Note that blobs are considered data and therefore will be included when --data-only is used, but not when --schema-only is.

-B --no-blobs

Exclude large objects in the dump.

When both -b and -B are given, the behavior is to output large objects, when data is being dumped, see the -b documentation.

-c --clean

Output commands to clean (drop) database objects prior to outputting the commands for creating them. (Unless --if-exists is also specified, restore might generate some harmless error messages, if any objects were not present in the destination database.)

This option is only meaningful for the plain-text format. For the archive formats, you can specify the option when you call pg_restore.

-C --create

Begin the output with a command to create the database itself and reconnect to the created database. (With a script of this form, it doesn't matter which database in the destination installation you connect to before running the script.) If --clean is also specified, the script drops and recreates the target database before reconnecting to it.

With --create, the output also includes the database's comment if any, and any configuration variable settings that are specific to this database, that is, any ALTER DATABASE ... SET ... and ALTER ROLE ... IN DATABASE ... SET ... commands that mention this database. Access privileges for the database itself are also dumped, unless --no-acl is specified.

This option is only meaningful for the plain-text format. For the archive formats, you can specify the option when you call pg_restore.

-E encoding --encoding=encoding

Create the dump in the specified character set encoding. By default, the dump is created in the database encoding. (Another way to get the same result is to set the PGCLIENTENCODINGenvironment variable to the desired dump encoding.)

-f file --file=file

Send output to the specified file. This parameter can be omitted for file based output formats, in which case the standard output is used. It must be given for the directory output format however, where it specifies the target directory instead of a file. In this case the directory is created by pg_dump and must not exist before.

-F format --format=format

Selects the format of the output. format can be one of the following:

p plain

Output a plain-text SQL script file (the default).

c custom

Output a custom-format archive suitable for input into pg_restore. Together with the directory output format, this is the most flexible output format in that it allows manual selection and reordering of archived items during restore. This format is also compressed by default.

d directory

Output a directory-format archive suitable for input into pg_restore. This will create a directory with one file for each table and blob being dumped, plus a so-called Table of Contents file describing the dumped objects in a machine-readable format that pg_restore can read. A directory format archive can be manipulated with standard Unix tools; for example, files in an uncompressed archive can be compressed with the gzip tool. This format is compressed by default and also supports parallel dumps.

t tar

Output a tar-format archive suitable for input into pg_restore. The tar format is compatible with the directory format: extracting a tar-format archive produces a valid directory-format archive. However, the tar format does not support compression. Also, when using tar format the relative order of table data items cannot be changed during restore.

-j njobs --jobs=njobs

同時執行匯出 njobs 個資料表。此選項可以節省匯出的時間，但同時也增加了資料庫伺服器上的負載。您只能將此選項與 directory 輸出格式一起使用，因為這是多個程序可以同時寫入資料的唯一輸出方式。

pg_dump 將打開 njobs + 1 個到資料庫的連線，因此請確保您的 max_connections 設定足夠多以容納所有連線。

在執行平行匯出時，對資料庫物件請求 exclusive locks (獨佔鎖定)可能會導致匯出失敗。原因是 pg_dump 主要程序會對工作程序稍後將要匯出的物件請求 shared locks (共享鎖定)，以確保沒有人會移除它們而在執行匯出時使它們消失。如果另一個用戶端隨後請求對資料進行獨佔鎖定，則不會授予該鎖定，它會排隊等待主要程序的共享鎖定被釋放。因此，對該資料表的任何其他存取也不會被允許，並且將排在排他鎖定請求之後。這當然也包括了嘗試匯出資料表的工作程序。如果沒有任何預防措施，這將是典型的 deadlock 情況。為了發現到這種衝突，pg_dump worker 程序使用 NOWAIT 選項請求另一個共享鎖定。如果未向工作程序授予該共享鎖定，那麼其他人在此期間必須已請求獨占鎖定，否則無法繼續進行匯出工作，因此 pg_dump 別無選擇，只能中止匯出。

為了實現備份的一致性，資料庫伺服器需要支援同步快照，這是 PostgreSQL 9.2 中針對主要伺服器引入的功能，針對備用伺服器引入了此功能是在版本 10 的時候。使用此功能，即使資料庫用戶端使用不同的連線，也可以確保他們看到相同的資料集。 pg_dump -j 使用多個資料庫連接； 它透過主要程序一次連線到資料庫，並針對每個工作程序再次連線到資料庫。如果沒有同步快照功能，將無法保證不同的工作程序在每個連線中都看到相同的資料，這就可能導致備份的不一致。

如果要在 9.2 之前版本伺服器的平行匯出，則需要確保從主伺服器連線到資料庫到最後一個工作程序作業連線到資料庫之間的時間裡，資料庫內容沒有變化。 最簡單的方法是在開始備份之前，停止所有資料庫的資料修改程序（包含 DDL 和 DML）。在9.2版之前的 PostgreSQL 服務器上執行 pg_dump -j 時，還需要指定 --no-synchronized-snapshots 參數。

-n schema --schema=schema

Dump only schemas matching schema; this selects both the schema itself, and all its contained objects. When this option is not specified, all non-system schemas in the target database will be dumped. Multiple schemas can be selected by writing multiple -n switches. Also, the schema parameter is interpreted as a pattern according to the same rules used by psql's \d commands (see Patterns), 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; see Examples.

Note

When -n is specified, pg_dump makes no attempt to dump any other database objects that the selected schema(s) might 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 --blobs switch.

-N schema --exclude-schema=schema

Do not dump any schemas matching the schema pattern. The pattern is interpreted according to the same rules as for -n. -N can be given more than once to exclude schemas matching any of several patterns.

When both -n and -N are given, the behavior is to dump just the schemas that match at least one -n switch but no -N switches. If -N appears without -n, then schemas matching -N are excluded from what is otherwise a normal dump.

-o --oids

Dump object identifiers (OIDs) as part of the data for every table. Use this option if your application references the OID columns in some way (e.g., in a foreign key constraint). Otherwise, this option should not be used.

-O --no-owner

Do not output commands to set ownership of objects to match the original database. By default, pg_dump issues ALTER OWNER or SET SESSION AUTHORIZATION statements 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 can specify the option when you call pg_restore.

-R --no-reconnect

This option is obsolete but still accepted for backwards compatibility.

-s --schema-only

Dump only the object definitions (schema), not data.

This option is the inverse of --data-only. It is similar to, but for historical reasons not identical to, specifying --section=pre-data --section=post-data.

(Do not confuse this with the --schema option, which uses the word “schema” in a different meaning.)

To exclude table data for only a subset of tables in the database, see --exclude-table-data.

-S username --superuser=username

Specify the superuser user name to use when disabling triggers. This is relevant only if --disable-triggers is used. (Usually, it's better to leave this out, and instead start the resulting script as superuser.)

-t table --table=table

僅匯出名稱與此選項相符的資料表。為此，“資料表”還包括檢視表、具體化檢視表、序列和外部資料表。透過寫入多個 -t 選項就可以選擇多個資料表。另外，根據 psql 的 \d 命令使用的相同規則，將 table 參數解釋為 pattern（請參閱 Patterns），因此也可以透過在 pattern 中寫入萬用字元來選擇多個資料表。使用萬用字元時，如果需要，請小心引用該樣式，以防止 Shell 擴展萬用字元。請參閱範例。

The -n and -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.

當指定 -t 時，pg_dump 不會嘗試匯出所選資料表可能相依的任何其他資料庫物件。因此，不能保證自己可以成功地將特定資料表匯出的結果還原到乾淨的資料庫中。

Note

The behavior of the -t switch is not entirely upward compatible with pre-8.2PostgreSQL versions. Formerly, writing -t tab would dump all tables named tab, but now it just dumps whichever one is visible in your default search path. To get the old behavior you can write -t '*.tab'. Also, you must write something like -t sch.tab to select a table in a particular schema, rather than the old locution of -n sch -t tab.-T table --exclude-table=table

Do not dump any tables matching the table pattern. The pattern is interpreted according to the same rules as for -t. -T can be given more than once to exclude tables matching any of several patterns.

When both -t and -T are given, the behavior is to dump just the tables that match at least one -t switch but no -T switches. If -T appears without -t, then tables matching -T are excluded from what is otherwise a normal dump.

-v --verbose

Specifies verbose mode. This will cause pg_dump to output detailed object comments and start/stop times to the dump file, and progress messages to standard error.

-V --version

Print the pg_dump version and exit.

-x --no-privileges --no-acl

Prevent dumping of access privileges (grant/revoke commands).

-Z 0..9 --compress=0..9

Specify the compression level to use. Zero means no compression. For the custom archive format, this specifies compression of individual table-data segments, and the default is to compress at a moderate level. For plain text output, setting a nonzero compression level causes the entire output file to be compressed, as though it had been fed through gzip; but the default is not to compress. The tar archive format currently does not support compression at all.

--binary-upgrade

This option is for use by in-place upgrade utilities. Its use for other purposes is not recommended or supported. The behavior of the option may change in future releases without notice.

--column-inserts --attribute-inserts

Dump data as INSERT commands with explicit column names (INSERT INTO table (column, ...) VALUES ...). This will make restoration very slow; it is mainly useful for making dumps that can be loaded into non-PostgreSQL databases. However, 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.

--disable-dollar-quoting

This option disables the use of dollar quoting for function bodies, and forces them to be quoted using SQL standard string syntax.

--disable-triggers

This option is relevant only when creating a data-only dump. It instructs pg_dump to include commands to temporarily disable triggers on the target tables while the data is reloaded. Use this if you have referential integrity checks or other triggers on the tables that you do not want to invoke during data reload.

Presently, the commands emitted for --disable-triggers must 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 can specify the option when you call pg_restore.

--enable-row-security

This option is relevant only when dumping the contents of a table which has row security. By default, pg_dump will set row_security to off, to ensure that all data is dumped from the table. If the user does not have sufficient privileges to bypass row security, then an error is thrown. This parameter instructs pg_dump to set row_security to on instead, allowing the user to dump the parts of the contents of the table that they have access to.

Note that if you use this option currently, you probably also want the dump be in INSERT format, as the COPY FROM during restore does not support row security.

--exclude-table-data=table

Do not dump data for any tables matching the table pattern. The pattern is interpreted according to the same rules as for -t. --exclude-table-data can be given more than once to exclude tables matching any of several patterns. This option is useful when you need the definition of a particular table even though you do not need the data in it.

To exclude data for all tables in the database, see --schema-only.

--if-exists

Use conditional commands (i.e. add an IF EXISTS clause) when cleaning database objects. This option is not valid unless --clean is also specified.

--inserts

Dump data as INSERT commands (rather than COPY). This will make restoration very slow; it is mainly useful for making dumps that can be loaded into non-PostgreSQL databases. However, 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 might fail altogether if you have rearranged column order. The --column-inserts option is safe against column order changes, though even slower.

--load-via-partition-root

When dumping data for a table partition, make the COPY or INSERT statements target the root of the partitioning hierarchy that contains it, rather than the partition itself. This causes the appropriate partition to be re-determined for each row when the data is loaded. This may be useful when reloading data on a server where rows do not always fall into the same partitions as they did on the original server. That could happen, for example, if the partitioning column is of type text and the two systems have different definitions of the collation used to sort the partitioning column.

It is best not to use parallelism when restoring from an archive made with this option, because pg_restore will not know exactly which partition(s) a given archive data item will load data into. This could result in inefficiency due to lock conflicts between parallel jobs, or perhaps even reload failures due to foreign key constraints being set up before all the relevant data is loaded.

--lock-wait-timeout=timeout

Do not wait forever to acquire shared table locks at the beginning of the dump. Instead fail if unable to lock a table within the specified timeout. The timeout may be specified in any of the formats accepted by SET statement_timeout. (Allowed formats vary depending on the server version you are dumping from, but an integer number of milliseconds is accepted by all versions.)

--no-comments

Do not dump comments.

--no-publications

Do not dump publications.

--no-security-labels

Do not dump security labels.

--no-subscriptions

Do not dump subscriptions.

--no-sync

By default, pg_dump will wait for all files to be written safely to disk. This option causes pg_dump to return without waiting, which is faster, but means that a subsequent operating system crash can leave the dump corrupt. Generally, this option is useful for testing but should not be used when dumping data from production installation.

--no-synchronized-snapshots

This option allows running pg_dump -j against a pre-9.2 server, see the documentation of the -j parameter for more details.

--no-tablespaces

Do not output commands to select tablespaces. With this option, all objects will be created in whichever tablespace is the default during restore.

This option is only meaningful for the plain-text format. For the archive formats, you can specify the option when you call pg_restore.

--no-unlogged-table-data

Do not dump the contents of unlogged tables. This option has no effect on whether or not the table definitions (schema) are dumped; it only suppresses dumping the table data. Data in unlogged tables is always excluded when dumping from a standby server.

--quote-all-identifiers

Force quoting of all identifiers. This option is recommended when dumping a database from a server whose PostgreSQL major version is different from pg_dump's, or when the output is intended to be loaded into a server of a different major version. By default, pg_dump quotes only identifiers that are reserved words in its own major version. This sometimes results in compatibility issues when dealing with servers of other versions that may have slightly different sets of reserved words. Using --quote-all-identifiers prevents such issues, at the price of a harder-to-read dump script.

--section=sectionname

Only dump the named section. The section name can be pre-data, data, or post-data. This option can be specified more than once to select multiple sections. The default is to dump all sections.

The data section contains actual table data, large-object contents, and sequence values. Post-data items include definitions of indexes, triggers, rules, and constraints other than validated check constraints. Pre-data items include all other data definition items.

--serializable-deferrable

Use a serializable transaction for the dump, to ensure that the snapshot used is consistent with later database states; but do this by waiting for a point in the transaction stream at which no anomalies can be present, so that there isn't a risk of the dump failing or causing other transactions to roll back with a serialization_failure. See Chapter 13 for more information about transaction isolation and concurrency control.

This option is not beneficial for a dump which is intended only for disaster recovery. It could be useful for a dump used to load a copy of the database for reporting or other read-only load sharing while the original database continues to be updated. Without it the dump may reflect a state which is not consistent with any serial execution of the transactions eventually committed. For example, if batch processing techniques are used, a batch may show as closed in the dump without all of the items which are in the batch appearing.

This option will make no difference if there are no read-write transactions active when pg_dump is started. If read-write transactions are active, the start of the dump may be delayed for an indeterminate length of time. Once running, performance with or without the switch is the same.

--snapshot=snapshotname

Use the specified synchronized snapshot when making a dump of the database (see Table 9.82 for more details).

This option is useful when needing to synchronize the dump with a logical replication slot (see Chapter 49) or with a concurrent session.

In the case of a parallel dump, the snapshot name defined by this option is used rather than taking a new snapshot.

--strict-names

Require that each schema (-n/--schema) and table (-t/--table) qualifier match at least one schema/table in the database to be dumped. Note that if none of the schema/table qualifiers find matches, pg_dump will generate an error even without --strict-names.

This option has no effect on -N/--exclude-schema, -T/--exclude-table, or --exclude-table-data. An exclude pattern failing to match any objects is not considered an error.

--use-set-session-authorization

Output SQL-standard SET SESSION AUTHORIZATION commands instead of ALTER OWNER commands to determine object ownership. This makes the dump more standards-compatible, but depending on the history of the objects in the dump, might not restore properly. Also, a dump using SET SESSION AUTHORIZATION will certainly require superuser privileges to restore correctly, whereas ALTER OWNER requires lesser privileges.

-? --help

Show help about pg_dump command line arguments, and exit.

The following command-line options control the database connection parameters.

-d dbname --dbname=dbname

Specifies the name of the database to connect to. This is equivalent to specifying dbname as the first non-option argument on the command line.

If this parameter contains an = sign or starts with a valid URI prefix (postgresql:// or postgres://), it is treated as a conninfo string. See Section 34.1 for more information.-

h host --host=host

Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket. The default is taken from the PGHOSTenvironment variable, if set, else a Unix domain socket connection is attempted.

-p port --port=port

Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default.

-U username --username=username

User name to connect as.

-w --no-password

Never issue a password prompt. If the server requires password authentication and a password is not available by other means such as a .pgpass file, the connection attempt will fail. This option can be useful in batch jobs and scripts where no user is present to enter a password.

-W --password

Force pg_dump to prompt for a password before connecting to a database.

This option is never essential, since pg_dump will automatically prompt for a password if the server demands password authentication. However, pg_dump will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.

--role=rolename

Specifies a role name to be used to create the dump. This option causes pg_dump to issue a SET ROLE rolename command after connecting to the database. It is useful when the authenticated user (specified by -U) lacks privileges needed by pg_dump, but can switch to a role with the required rights. Some installations have a policy against logging in directly as a superuser, and use of this option allows dumps to be made without violating the policy.

Environment

PGDATABASE PGHOST PGOPTIONS PGPORT PGUSER

Default connection parameters.

This utility, like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Section 34.14).

Diagnostics

pg_dump internally executes SELECT statements. If you have problems running pg_dump, make sure you are able to select information from the database using, for example, psql. Also, any default connection settings and environment variables used by the libpq front-end library will apply.

The database activity of pg_dump is normally collected by the statistics collector. If this is undesirable, you can set parameter track_counts to false via PGOPTIONS or the ALTER USER command.

Notes

If your database cluster has any local additions to the template1 database, be careful to restore the output of pg_dump into a truly empty database; otherwise you are likely to get errors due to duplicate definitions of the added objects. To make an empty database without any local additions, copy from template0 not template1, for example:

CREATE DATABASE foo WITH TEMPLATE template0;

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 then commands to re-enable them after the data has been inserted. If the restore is stopped in the middle, the system catalogs might be left in the wrong state.

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 optimal performance; see Section 24.1.3 and Section 24.1.6 for more information.

Because pg_dump is used to transfer data to newer versions of PostgreSQL, the output of pg_dump can be expected to load into PostgreSQL server versions newer than pg_dump's version. pg_dumpcan also dump from PostgreSQL servers older than its own version. (Currently, servers back to version 8.0 are supported.) However, pg_dump cannot dump from PostgreSQL servers newer than its own major version; it will refuse to even try, rather than risk making an invalid dump. Also, it is not guaranteed that pg_dump's output can be loaded into a server of an older major version — not even if the dump was taken from a server of that version. Loading a dump file into an older server may require manual editing of the dump file to remove syntax not understood by the older server. Use of the --quote-all-identifiers option is recommended in cross-version cases, as it can prevent problems arising from varying reserved-word lists in different PostgreSQL versions.

When dumping logical replication subscriptions, pg_dump will generate CREATE SUBSCRIPTION commands that use the NOCONNECT option, so that restoring the subscription does not make remote connections for creating a replication slot or for initial table copy. That way, the dump can be restored without requiring network access to the remote servers. It is then up to the user to reactivate the subscriptions in a suitable way. If the involved hosts have changed, the connection information might have to be changed. It might also be appropriate to truncate the target tables before initiating a new full table copy.

範例

要將名稱為 mydb 的資料庫匯出到 SQL 腳本檔案中：

$ pg_dump mydb > db.sql

要將這樣的腳本重新載入到名稱為 newdb 的（新建立的）資料庫中：

$ psql -d newdb -f db.sql

To dump a database into a custom-format archive file:

$ pg_dump -Fc mydb > db.dump

To dump a database into a directory-format archive:

$ pg_dump -Fd mydb -f dumpdir

To dump a database into a directory-format archive in parallel with 5 worker jobs:

$ pg_dump -Fd mydb -j 5 -f dumpdir

To reload an archive file into a (freshly created) database named newdb:

$ pg_restore -d newdb db.dump

To reload an archive file into the same database it was dumped from, discarding the current contents of that database:

$ pg_restore -d postgres --clean --create db.dump

只要單獨匯出名稱為 mytab 的資料表：

$ pg_dump -t mytab mydb > db.sql

要在 detroit 綱要中匯出所有名稱以 emp 開頭的資料表，但名稱為 employee_log 的資料表除外：

$ pg_dump -t 'detroit.emp*' -T detroit.employee_log mydb > db.sql

To dump all schemas whose names start with east or west and end in gsm, excluding any schemas whose names contain the word test:

$ pg_dump -n 'east*gsm' -n 'west*gsm' -N '*test*' mydb > db.sql

The same, using regular expression notation to consolidate the switches:

$ pg_dump -n '(east|west)*gsm' -N '*test*' mydb > db.sql

To dump all database objects except for tables whose names begin with ts_:

$ pg_dump -T 'ts_*' 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 (see Patterns). 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

參閱

pg_dumpall, pg_restore, psql