I have two databases on the same server. One named A and one named B. Booth databases have the same structure. I want to empty database B and load it with data from database A. Which is the best way to do this?
I have tried to take backup of database A in plain format. Then open the resulting sql-file and replace every occurence of 'A' with 'B' and then run the sql-script. This worked but I think it should be an easier way to move data from one database to another. Is it?
I use 'pgAdmin III' as my tool, but this is not necessary.
This is my first post here, hope the question is relevant and structured well enough. I tried google first but found it hard to find anyone with the same question.
Thanks in advance!
/David
SOLUTION: After help from Craig, this is how I did it
pg_dump -Fc -a -f a.dbbackup A
psql -c 'TRUNCATE table1, table2, ..., tableX CASCADE'
pg_restore dblive.backup -d B -c (not sure if -c was necessary)
Backup:
pg_dump -Fc -f a.dbbackup
Restore:
psql -c 'CREATE DATABASE b;'
pg_restore --dbname b a.dbbackup
Use the -U, -h etc options as required to connect to the correct host as the correct user with permissions to dump, create and restore the DB. See the docs for psql, pg_dump and pg_restore for more info (they all take the same options for connection control).
Related
I have a dump file (size around 5 GB) which is taken via this command:
pg_dump -U postgres -p 5440 MYPRODDB > MYPRODDB_2022.dmp
The database consists multiple schemas (let's say Schema A,B,C and D) but i need to restore only one schema (schema A).
How can i achieve that? The command below didn't work and gave error:
pg_restore -U postgres -d MYPRODDB -n A -p 5440 < MYPRODDB_2022.dmp
pgrestore: error: input file appears to be a text format dump. please
use psql.
You cannot do that with a plain format dump. That's one of the reasons why you always use a different format unless you need an SQL script.
If you want to stick with a plain text dump:
pg_dump -U postgres -p 5440 -n A MYPRODDB > MYPRODDB_2022.dmp
psql -U postgres -d MYPRODDB -p 5440 -f MYPRODDB_2022.dmp
Though dumping back over the same database as above will throw errors unless you use --clean or its short form -c to create commands to drop existing objects before restoring them:
-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 pg_restore.
Probably also a good idea to throw in --if-exists:
--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.
I try to restore a large table
pg_restore.exe -U postgres -d db_name --clean --if-exists --single-transaction F:\Backups\PostgreSQL\data.dump.gz
So I have a read lock for a few minutes. How to restore data with zero downtime for reading? I need only reading.
You would need to not do the --clean and instead do --data-only, but then do a DELETE from tablename inside the same transaction, before the COPY. I don't think there is a way to make pg_restore do this for you, but you could dump the output of pg_restore to a file and edit it, or use something like sed or perl to inject the DELETE.
This should work for table names which don't need to be quoted, and assuming none of the data being copied has first column which starts with 'COPY ':
pg_restore --data-only --single-transaction dmp.dmp -f -| perl -pe 's/^COPY ([\w.]+)/delete from $1; copy $1/' | psql -U postgres -d db_name
However, your schema changing method doesn't seem so dirty to me. It still requires a momentary access exclusive lock, so it isn't really zero downtime, but it might be unnoticable downtime if it can acquire said lock quickly enough.
I want to restore a database from backup and rewrite all data that is there with backup data.
My current command is like this:
pg_restore -h localhost -U postgres -d dbName -v autobackup_file.dmp
How to restore and rewrite all data?
I've seen an option -c; is that the correct way?
And where should I put it in my command?
-c can be anywhere, e.g. immediately after pg_restore.
It will DROP all restored objects before restoring them, but it will not drop any objects that are not in the dump.
To drop and recreate the whole database so you get a clean copy, you can use -C -c.
I have a database with some tables for the application settings, lists like users, departments, cities. I want the structure and the data for those tables. So if i get a new user the backup will save it.
But also have some data for historic and calculated data, that data came from another sources and only work for some time and then expire, so backup that data will be a waste. But will need have the structure so the restore will create the tables need it for the application.
right now I'm using this command but this save all table and all data.
pg_dump -U "postgres" -h "local" -p "5432"
-d dbName -F c -b -v -f c:\uti\backup.dmp
I have 2 additional questions regarding pg_dump.
A) docs say option -b is for blob data. I have very big tables, but i guess this options is for only tables with a BLOB field, so shouldn't make any difference in my backup because i don't have those fields ?.
B) I see pg_dump options are for tables and schemas. How you specify if want save the functions code?
Exclude the tables you do not want to backup
pg_dump -U "postgres" -h "local" -p "5432"
-d dbName -F c -b -v -f c:\uti\backup.dmp
--exclude-table-data '*.table_name_pattern_*'
--exclude-table-data 'some_schema.another_*_pattern_*'
The function creation code is part of the schema.
Clodoaldo Neto's is the way to go. However, I witnessed a strange behavior when using pg_dump with capital letters. The issue is also described here
So in my case the table to ignore was named ChangeHistory and the trick to ignore it was wildcarding capital letters as below
pg_dump [omitted for brievity] --exclude-table "*hange*istory"
How to get my db structure without the data, (schema, tables, ...) as a script by command line.
http://www.postgresql.org/docs/current/interactive/app-pgdump.html
pg_dump -s -U username database > backup.sql
Haven't tested it though, so not sure if it works.
edit: had the german link up there ;)