lt_dump — extract a LightDB database into a script file or other archive file
lt_dump
[connection-option
...] [option
...] [dbname
]
lt_dump is a utility for backing up a LightDB database. It makes consistent backups even if the database is being used concurrently. lt_dump does not block other users accessing the database (readers or writers).
lt_dump only dumps a single database. To back up an entire cluster, or to back up global objects that are common to all databases in a cluster (such as roles and tablespaces), use lt_dumpall.
Dumps can be output in script or archive file formats. Script dumps are plain-text files containing the SQL commands required to reconstruct the database to the state it was in at the time it was saved. To restore from such a script, feed it to ltsql. Script files can be used to reconstruct the database even on other machines and other architectures; with some modifications, even on other SQL database products.
The alternative archive file formats must be used with lt_restore to rebuild the database. They allow lt_restore to be selective about what is restored, or even to reorder the items prior to being restored. The archive file formats are designed to be portable across architectures.
When used with one of the archive file formats and combined with
lt_restore,
lt_dump provides a flexible archival and
transfer mechanism. lt_dump can be used to
backup an entire database, then lt_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.
lt_dump support dump plorasql packages and procedures, like dump tables and so on.
While running lt_dump, one should examine the output for any warnings (printed on standard error), especially in light of the limitations listed below.
The following command-line options control the content and format of the output.
dbname
Specifies the name of the database to be dumped. If this is
not specified, the environment variable
LTDATABASE
is used. If that is not set, the
user name specified for the connection is used.
-a
--data-only
Dump only the data, not the schema (data definitions). Table data, large objects, and sequence values are dumped.
This option is similar to, but for historical reasons not identical
to, specifying --section=data
.
-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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_restore
.
-K
--recreate-schema
Output commands to directly drop schema(use cascade mode) prior to outputting the commands for creating them, more faster then normal mode.
(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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_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 LTCLIENTENCODING
environment
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 lt_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 lt_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 lt_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 lt_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 lt_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
Run the dump in parallel by dumping njobs
tables simultaneously. This option may reduce the time needed to perform the dump but it also
increases the load on the database server. You can only use this option with the
directory output format because this is the only output format where multiple processes
can write their data at the same time.
lt_dump will open njobs
+ 1 connections to the database, so make sure your max_connections
setting is high enough to accommodate all connections.
Requesting exclusive locks on database objects while running a parallel dump could
cause the dump to fail. The reason is that the lt_dump master process
requests shared locks on the objects that the worker processes are going to dump later
in order to
make sure that nobody deletes them and makes them go away while the dump is running.
If another client then requests an exclusive lock on a table, that lock will not be
granted but will be queued waiting for the shared lock of the master process to be
released. Consequently any other access to the table will not be granted either and
will queue after the exclusive lock request. This includes the worker process trying
to dump the table. Without any precautions this would be a classic deadlock situation.
To detect this conflict, the lt_dump worker process requests another
shared lock using the NOWAIT
option. If the worker process is not granted
this shared lock, somebody else must have requested an exclusive lock in the meantime
and there is no way to continue with the dump, so lt_dump has no choice
but to abort the dump.
For a consistent backup, the database server needs to support
synchronized snapshots, a feature that was introduced in
LightDB 9.2 for primary servers and 10
for standbys. With this feature, database clients can ensure they see
the same data set even though they use different connections.
lt_dump -j
uses multiple database connections; it
connects to the database once with the master process and once again
for each worker job. Without the synchronized snapshot feature, the
different worker jobs wouldn't be guaranteed to see the same data in
each connection, which could lead to an inconsistent backup.
If you want to run a parallel dump of a pre-9.2 server, you need to make sure that the
database content doesn't change from between the time the master connects to the
database until the last worker job has connected to the database. The easiest way to
do this is to halt any data modifying processes (DDL and DML) accessing the database
before starting the backup. You also need to specify the
--no-synchronized-snapshots
parameter when running
lt_dump -j
against a pre-9.2 LightDB
server.
-n pattern
--schema=pattern
Dump only schemas matching pattern
; 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. The
pattern
parameter is
interpreted as a pattern according to the same rules used by
ltsql's \d
commands
(see Patterns below),
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 below.
When -n
is specified, lt_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.
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 pattern
--exclude-schema=pattern
Do not dump any schemas matching 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
--no-owner
Do not output commands to set
ownership of objects to match the original database.
By default, lt_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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_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 pattern
--table=pattern
Dump only tables with names matching
pattern
. Multiple tables
can be selected by writing multiple -t
switches. The
pattern
parameter is
interpreted as a pattern according to the same rules used by
ltsql's \d
commands
(see Patterns below),
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; see
Examples below.
As well as tables, this option can be used to dump the definition of matching
views, materialized views, foreign tables, and sequences. It will not dump the
contents of views or materialized views, and the contents of foreign tables will
only be dumped if the corresponding foreign server is specified with
--include-foreign-data
.
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.
When -t
is specified, lt_dump
makes no attempt to dump any other database objects that the selected
table(s) might 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.
The behavior of the -t
switch is not entirely upward
compatible with pre-8.2 LightDB
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 pattern
--exclude-table=pattern
Do not dump any tables matching 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 lt_dump to output detailed object comments and start/stop times to the dump file, and progress messages to standard error.
-V
--version
Print the lt_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 and directory archive formats, 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
). This will make restoration very slow; it is mainly
useful for making dumps that can be loaded into
non-LightDB databases.
Any error during restoring will cause only rows that are part of the
problematic table
(column
, ...) VALUES
...INSERT
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 lt_dump to include commands to temporarily disable triggers on the target tables while the data is restored. Use this if you have referential integrity checks or other triggers on the tables that you do not want to invoke during data restore.
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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_restore
.
--enable-row-security
This option is relevant only when dumping the contents of a table which has row security. By default, lt_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 lt_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=pattern
Do not dump data for any tables matching 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
.
--extra-float-digits=ndigits
Use the specified value of extra_float_digits
when dumping
floating-point data, instead of the maximum available precision.
Routine dumps made for backup purposes should not use this option.
--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.
--include-foreign-data=foreignserver
Dump the data for any foreign table with a foreign server
matching foreignserver
pattern. Multiple foreign servers can be selected by writing multiple
--include-foreign-data
switches.
Also, the foreignserver
parameter is
interpreted as a pattern according to the same rules used by
ltsql's \d
commands
(see Patterns below),
so multiple foreign servers 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 below.
The only exception is that an empty pattern is disallowed.
When --include-foreign-data
is specified,
lt_dump does not check that the foreign
table is writable. Therefore, there is no guarantee that the
results of a foreign table dump can be successfully restored.
--lt-exclude-lightdb-objects
Exclude all built-in objects created by LightDB in the dump.
For built-in tables or schemas created by LightDB, when both
-t
or -n
are given, the behavior is
to ignore the table or the schema, when data is being dumped, see the
-t
and -n
documentation.
--lt-dump-lightdb-tables
Dump only the data of built-in tables which specified in 'pg_extension_config_dump' (in the extension's SQL scripts).
This tables will be truncate firstly when data is being restored.
When both -s
or --section
are given,
the behavior is to ignore the table data, when data is being dumped.
For built-in tables created by LightDB, when
--exclude-table-data
are given, the behavior is to
ignore the table data, when data is being dumped, see the
--exclude-table-data
documentation.
For built-in tables created by LightDB, when
-t
are given, dump only the data of tables with names
matching pattern
.
For built-in tables created by LightDB, when
-T
are given, exclude the tables with names
matching pattern
.
For built-in tables created by LightDB, when
-n
are given, dump only the data of tables under the
schema with names matching
pattern
.
For built-in tables created by LightDB, when
-N
are given, exclude the tables under the schema
with names matching pattern
.
Options --lt-exclude-lightdb-objects and --lt-dump-lightdb-tables cannot be used together.
--lt-disable-auto-analyze
Do not automatic collect statistics when dump index. (see CREATE INDEX for more details).
--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-LightDB databases.
Any error during restoring will cause only rows that are part of the
problematic INSERT
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 restoring 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 lt_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 restore 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, lt_dump
will wait for all files
to be written safely to disk. This option causes
lt_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 lt_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 ignored when emitting an archive (non-text) output
file. For the archive formats, you can specify the option when you
call lt_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.
--on-conflict-do-nothing
Add ON CONFLICT DO NOTHING
to
INSERT
commands.
This option is not valid unless --inserts
,
--column-inserts
or
--rows-per-insert
is also specified.
--quote-all-identifiers
Force quoting of all identifiers. This option is recommended when
dumping a database from a server whose LightDB
major version is different from lt_dump's, or when
the output is intended to be loaded into a server of a different
major version. By default, lt_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.
--rows-per-insert=nrows
Dump data as INSERT
commands (rather than
COPY
). Controls the maximum number of rows per
INSERT
command. The value specified must be a
number greater than zero. Any error during restoring will cause only
rows that are part of the problematic INSERT
to be
lost, rather than the entire table contents.
--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 lt_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 9.89 for more details).
This option is useful when needing to synchronize the dump with a logical replication slot (see Chapter 45) 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, lt_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 lt_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. The dbname
can be a connection string.
If so, connection string parameters will override any conflicting
command line options.
-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 LTHOST
environment 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 LTPORT
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 lt_dump to prompt for a password before connecting to a database.
This option is never essential, since
lt_dump will automatically prompt
for a password if the server demands password authentication.
However, lt_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 lt_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 lt_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.
LTDATABASE
LTHOST
LTOPTIONS
LTPORT
LTUSER
Default connection parameters.
LT_COLOR
Specifies whether to use color in diagnostic messages. Possible values
are always
, auto
and
never
.
This utility, like most other LightDB utilities, also uses the environment variables supported by libpq (see Section 32.14).
lt_dump internally executes
SELECT
statements. If you have problems running
lt_dump, make sure you are able to
select information from the database using, for example, ltsql. Also, any default connection settings and environment
variables used by the libpq front-end
library will apply.
The database activity of lt_dump is
normally collected by the statistics collector. If this is
undesirable, you can set parameter track_counts
to false via LTOPTIONS
or the ALTER
USER
command.
If your database cluster has any local additions to the template1
database,
be careful to restore the output of lt_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, lt_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 lt_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 22.1.3
and Section 22.1.6 for more information.
Because lt_dump is used to transfer data
to newer versions of LightDB, the output of
lt_dump can be expected to load into
LightDB server versions newer than
lt_dump's version. lt_dump can also
dump from LightDB servers older than its own version.
(Currently, servers back to version 8.0 are supported.)
However, lt_dump cannot dump from
LightDB 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 lt_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 LightDB versions.
When dumping logical replication subscriptions,
lt_dump will generate CREATE
SUBSCRIPTION
commands that use the connect = false
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.
To dump a database called mydb
into a SQL-script file:
$
lt_dump mydb > db.sql
To reload such a script into a (freshly created) database named
newdb
:
$
ltsql -d newdb -f db.sql
To dump a database into a custom-format archive file:
$
lt_dump -Fc mydb > db.dump
To dump a database into a directory-format archive:
$
lt_dump -Fd mydb -f dumpdir
To dump a database into a directory-format archive in parallel with 5 worker jobs:
$
lt_dump -Fd mydb -j 5 -f dumpdir
To reload an archive file into a (freshly created) database named
newdb
:
$
lt_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:
$
lt_restore -d postgres --clean --create db.dump
To dump a single table named mytab
:
$
lt_dump -t mytab mydb > db.sql
To dump all tables whose names start with emp
in the
detroit
schema, except for the table named
employee_log
:
$
lt_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
:
$
lt_dump -n 'east*gsm' -n 'west*gsm' -N '*test*' mydb > db.sql
The same, using regular expression notation to consolidate the switches:
$
lt_dump -n '(east|west)*gsm' -N '*test*' mydb > db.sql
To dump all database objects except for tables whose names begin with
ts_
:
$
lt_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 below). 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
$
lt_dump -t "\"MixedCaseName\"" mydb > mytab.sql